DR650 FAQ - Fuel System
I want to replace the leaking vacuum style petcock. Your replacement manual petcocks say "must be turned off if the bike sits for more than a few hours". Why is this? Does this carburetor have something that allows the fuel to not be shut off at the floats or something?A:
In a perfect world the float valve will stop the flow of fuel into the carburetor except for when the carburetor needs more. Most of the time you can get away with forgetting to turn the fuel off, but if the float valve leaks, even just a little, all the fuel in the tank could end up in the engine crankcase mixed with the oil, and/or all over the floor of the garage. That’s bad news for your engine and of course a fire hazard. This is the reason the stock petcock is vacuum operated. It shuts the fuel off for you every time the motor is shut off.
I'm about ready to go ahead with an order for the TM40. Info on your site indicates you can set it up for modifications I have already made to my bike. I have a 2006 DR650 with the airbox top cut out and a GSXR muffler with Two Bros. mid pipe installed. I have ground down the header weld as well. I want to use the stock choke lever and I have a taller handlebar mount & bars. The stock throttle cables are a little on the tight side in this configuration. Anything else I need to tell you before I place my order?A:
Our standard jetting setup will be just right for your mods. You should have no problem keeping your choke in the stock location either. We do offer a remote choke assembly that puts the choke in an easy to reach location. If your throttle cables are tight you might consider inverting the throttle housing so the cables are running under the bar. That will give you a couple additional inches of cable length. That is all we need to get your carb headed your way!
I'm having trouble routing the TM40 throttle cables. It looks like the elbows bend the wrong way. Did I get the wrong cables?A:
I put the TM40 on my 2007 DR650 about 2 weeks ago. I also installed a FMF Q2 and put a 2" hole in the top of the air box and removed the snorkel. Pretty much like the other responses I've read, the bike runs great with the TM-40. It has improved throttle response, and I don't have to shift as often because the bike is much more tractable across a broader RPM range. I've got a 14 CS sprocket on, and the bike pulls hard up to an indicated 100 mph. I'm not sure where the rev limiter kicks in, but it winds up fast to 100 mph and wants to keep going. I'm getting about the same mileage as I was with the stock BST. The bike will go just over 100 miles before it hits reserve, which if I figured right is 42 - 45 mpg. Most of my riding is stop-n-go on surface streets, and I ride fairly hard on the throttle. But the mileage has been the about same on highway trips.
I think the TM-40 carb may be a tad rich. The exhaust smells like it did with the BST, no gas odor. But, the bike did need a little choke for about 30 seconds to get going in the morning with the BST. With the TM-40 the bike starts INSTANTLY with no choke. There is a slight blip on initial throttle and between shifts, other than that, it rips.
OK, after all of that here's the question, do you think I need to make adjustments, and if so, where do you recommend that I start? Personally, I'm reluctant to start changing settings for effect, because it runs very well as is.
I'm interested in the Twin-Air filter for the DR650. Does it flow any better than the stock filter? I don't want the K&N filter. Sorry about the length here. I thought it's better to tell you what I know, than for you to have to ask later. Thanks for your help, I'm very pleased with the TM-40 kit.A:
The blip between shifts should be addressed. It's getting a little bit too much fuel at the initial opening of the throttle. What it needs is more gap between the top of the accelerator pump rod and the white nylon arm that actuates it. This can be adjusted with a small phillips screw on the upper right hand side of the carb. I'd also suggest lowering the needle (raising the clip) one notch to improve fuel mileage.
Starting easily with no choke is definitely a sign of being too rich at idle. Screw the mixture screw in until you can just notice the idle start to drop. You want the screw set right at the cusp of idle speed drop.
The Twin Air filter flows much better than the stock filter - on par with the K&N. Only change one thing at a time though! Then test ride thoroughly between changes so you can gauge the individual changes on their own.
Are the throttle cables supplied with the TM40 carburetor kit for the DR650 the same as the stock Suzuki cables, or are different throttle cables required for the TM40 conversion? The reason I'm asking is because my DR650 is less than a year old, and the throttle cables should be good for some time. If different throttle cables aren't required, how much do they add to the cost of the kit?
Also I have some reservation about cutting open the top of the air box (Jessie's mod). I've discussed tuning the bike with a mechanic I've had work on other bikes, and he recommended removing the air box and using a pod filter. Other than avoiding water crossings (which I do anyway), is there any other reason to run a modified air box?A:
The stock cables are too long to work on the TM40. We have cables custom made to work with the new carburetor. The reason people modify the airbox is the DynoJet jet kit is designed to work correctly only with a modified airbox. The airbox doesn't have to be modified to run the TM40 but it will be much easier to tune and make more power with a modified airbox..
I would not recommend using a pod filter. I don't have any jetting test data for that setup so you would be on your own as far as finding a jetting setup that would work without the airbox.
I just picked up a TM40 from a local riding buddy who took it off of a Harley. I need some jetting advice for initial setup for my typical riding of sea level to about 7000 feet. I'm also planning to do the GDR, so I'll need to get the jets for altitude also. The meat of the Colorado/Wyoming part is around 8000 feet +/- with a few passes going over 10,000 feet. Currently the bike is set-up with the stock exhaust and the snorkel removed from the airbox and 1" hole added in the top. I've searched and people with similar setups have used anywhere between 127.5 and 140 for the main and 17.5 to 20 for the pilot. The 17.5 pilot seems to have a pretty wide range so I'll probably go with that one. Will the 17.5 work OK at altitude or should I pack a 15 just in case?
For my standard riding elevations, I'm thinking the 132.5 or 135 is a good starting point. For the GDR, maybe start the ride on the lean side at 130 and pack something leaner to swap if it starts bogging. How small do I need to go at those altitudes?A:
One thing to be aware of if you are using a TM40 off a Harley is that the accelerator pump nozzle is way too big. You need to drop it down to a 40 or 45. As for the other jets, a 150 main and 22.5 pilot works fine for me from sea level to 9500 feet. No carb adjustments needed. That's with open airbox and FMF Q4 exhaust. The key to acceptable running at altitude is to jet on the lean edge of the 'good running' envelope at your home elevation. I doubt the 17.5 pilot will work very well for you. The TM40 works really well with stock equipment, but it functions much better with a different silencer (breathe better) and the top cut out of the airbox allowing it to breathe better.
Some people are putting the Keihin FCR39 on their DR650s. How does the FCR compare with the Mikuni TM40?A:
Each carb has both good and bad attributes when compared to the other. The FCR is a more advanced carburetor but that also makes it a more complicated piece of hardware as compared to the Mikuni. The Mikuni is very simple and straightforward to make jetting changes. The FCR has the 'coast enrichener' that will decrease (but not eliminate) the annoying popping on deceleration. The TM40 will pop just like the stock BST. The TM40 (kit) is a brand new carb and therefore a known quantity. Most FCR conversions will start out with a used YFZ450 carb of maybe questionable history.
If you can score a good deal on a good used FCR then you can do the whole conversion for less money than the full TM40 kit. In my opinion the FCR is more suited to the guy who is more of a hands-on tinkerer. Someone who is not afraid to delve into a used carb, modify and re-jet it and evaluate the success of his efforts.
The TM40 (kit) is probably a better choice for the guy who feels comfortable swapping out carburetors but doesn't really want to become intimately familiar with internal carburetor parts.
Do you have a standard jetting you would recommend I start with once I've installed the exhaust & done the airbox mod? I live at approximately sea level and won't normally be going any higher than a max of about 4,000 to 5,000 feet (I live in the Northeast and do travel up to Mt. Washington/Green Mountains from time to time and do frequent the Berkshires).A:
We haven't done much jetting work with the stock carburetor. With a cut airbox you will need a DynoJet jet kit (we sell them in Moose Racing packaging). Probably a DJ160 main and needle in 3rd or 4th notch. Again, we have not done much jetting work with the stock carb since I switched over to the Mikuni TM40 pumper.
My Dynojet kit instructions say to remove the side cover from the airbox. It's really noisy with that cover off though. Is there anything else I can do?A:
Yes. the intake honk echoing off the left side cover can be annoying. Instead, you can leave the airbox lid in place and cut out the top of the airbox. I used a knife that I heated up with a torch to cut out the top and the upper sections on the sides. Click on the pics below to see larger images.
I have a 2007 DR650 and just recently removed the snorkel and am ready to do other modifications for additional power. What should I do next?A:
The simple, easy next step is to shim the carburetor needle up by about .030". Just removing the snorkel is only a benefit if you also raise the needle. If you want to install a DynoJet jet kit you will need to not only remove the snorkel but also cut out the top of the airbox (or remove the airbox side cover). This allows the motor to get more air.
I recently removed the snorkel from my airbox and shimmed the needle 1.5 mm. Is that right?A:
That is a bit too much, should be 0.5 to 1 mm (.020" to .040"). More than that and fuel economy will suffer.
I have a new (to me) 1996 DR650. The airbox is cut open. I asked the fellow I bought it from if the jetting had been revised and he said that he did not do the airbox modification, that the fellow who owned it before him did the modification and revised the jetting. What I want to know is if there is a way that I can check to make sure that the jetting was revised.A:
If the bike runs decent then the jetting has been revised. A bike with a modified airbox and stock jetting will be just about impossible to ride. That said, you still want to take it apart, inspect everything and make notes as to how it actually has been set up, for future reference. A lot of folks doing the rejet will end up with a setup that is too rich. If it runs OK but you aren't getting close to 50 mpg during moderate riding, then the jetting setup could use some work.
I just bought a '96 DR650. It ran great on my test ride, but after I got it home (four hours in the back of my truck in the extreme cold, it would barely start and run. Next day, I get it running, but it just will NOT throttle up with out stumbling and backfiring. The odd thing is that it ALMOST corrects itself as the bike gets warmed up (idles for about 10 minutes or more.) Previous owner stated that he always had to let it warm up with the choke on for 10 minutes to get rid of it. I've been searching this forum for info, and found some help but nothing has completely fixed it. The bike is stock in all ways that I know. So here's what I've done:
- Checked the plugs (carbon present, cleaned them up)
- Completely cleaned the carburetor and cleaned the jets (all stock sizes) and then blew them out with compressed air
- Turned out idle screw
- Adjusted the valves
- Cleaned contacts in coil wiring harness
- Put in fresh gas
- Petcock is set on 'prime'
I'm sure it can be ironed out, I'm just curious why it gets "better" as it warms up.A:
Getting better when hot tells you it is pretty likely a lean mixture problem. Something is causing it not to get enough fuel in the range where the poor running occurs. Have any airbox modifications been done? It sounds like a bike that has airbox mods but no jetting mods to go with it.
How well did it pull the 17/42 gearing with the flatslide carburetor? That seems pretty tall. Can you go from the 13 to 17 using the same chain length? The biggest reason I have stayed with the CV carburetor, besides lack of funds, is the altitude change around here. In a day’s riding it is possible to have 5,000 to 6,000 feet of elevation change and the CV carb seems to handle that pretty well.A:
Yes, you can go from 13 to 17 on the countershaft sprocket with the stock length chain. 17/42 gearing works better with the flatslide but the stock carb will pull it just fine as long as you don't let the revs drop too low. It puts 5th gear right where my imaginary 6th gear would be. The TM40 isn't bothered by altitude changes. I've run mine from sea level to 9,500 feet without a hitch. Click here if you have more questions about the TM40 carburetor swap.
My DR650 can be difficult to start at times, what can I do to make it easier?A:
The DR650s can be adjusted on the lean side to meet EPA regulations. The easiest thing to do, and it will probably cure the problem, is to adjust the fuel mixture screw. The only problem is, it is covered up! If you remove the carburetor and look just forward of the float bowl, you will see a little brass plug. That is what you need to remove. To do that, simply drill a small hole in the plug, thread in a small sheet metal screw just far enough to get a turn or two into the plug, and then grab the screw with a pair of pliers and pull it out. That simple.
Once you have the plug removed, you will be able to see the fuel mixture screw down in that recess. A good place to start with the stock carb is about 1-1/2 turns out. Turn the screw in all the way until it seats, then turn it back out one and a half turns. This screw can be difficult to reach as it is located in a very narrow recess. We do off an extended fuel screw that makes it much easier to fine tune the idle mixture. Though the pictures are for an XT225 carburetor, click here to see a very good tutorial with pictures on the XT225.com forum of how to do this operation.
My bike hasn’t been ridden much lately due to the weather. It is just now getting nice enough out, so I broke the old DR out the other day and it was very difficult to start. I needed to cover up the intake to get it going. Then I took the carburetor apart to check the choke and see if that was the problem. It seemed fine, so I put in a new Needle and Needle Jet. Then I cleaned the entire unit out as best I could, but it didn't’t seem to make any improvement. Once the beast gets warmed up it seems to run fine.A:
There's a well in the float bowl that feeds the enrichener circuit. That well usually has a very small orifice in the bottom where fuel passes from the bowl into the well. Make sure that passage is not blocked.
I have a stock 1999 DR350SE with just over 5,000 miles. It has been stored away for quite some time and I did not treat the fuel in any fashion before storing it. When I pulled it out of storage it did not run so good. It idled OK, but stumbled just above idle. If I roll the gas on smoothly up through the RPM’s, it seems fine, but if I roll it on pretty hard, it just stumbles and falls on its face. I did go through and clean the carburetor out with carburetor cleaner, but that didn’t help much, if at all.A:
The most critical part of cleaning a gummed up carburetor is to remove the pilot jet and make sure the passage inside it is perfectly clean and not even partially blocked. It sounds like all you did was spray the cleaner on everything and just isn't enough to do the job.
I have seen a few sets of snowmobile carburetors on eBay, are these the same carburetor as your TM40 kit for the DR650?A:
No! These are not ‘pumper’ cards. These are designed and built for 2-strokes and do not have an accelerator pump. They also do not come with all of the parts necessary to make installation on your DR a snap. You DO NOT get the steel adapter ring bonded to the carburetor body for a firm, reliable fit in the stock air boot; new cables; a wide range of extra jetting for fine tuning; extended fuel screw and detailed instructions, all of which are included in our TM40 kit. We also include a knob type choke (even though the stock cable choke fits perfectly). This carburetor even has a vacuum port for the stock fuel petcock and is pre-jetted for the typical performance modifications of a pipe and modified airbox, or we can set it up for your particular bike before we ship it out.
Just so I understand, can you explain the difference between a 'pumper' and regular carburetor? Second, what dimension on a carburetor determines the size of a carburetor?A:
The 'pumper' designation refers to the carburetor having an accelerator pump that gives a small squirt of fuel any time the throttle is opened. With a pumper carb you can usually run leaner jetting (better fuel economy). Without the pump you usually have to run the needle a bit richer to be sure to get the desired throttle response. Second, the size of the carburetor is determined by the size of the opening through the body near the needle.
I want to install a pumper on the thumper, and need a kit. I was wondering what the difference is between the ProCycle and Kientech kits besides the adapter that you include in your kit. Do you really need the adapters? Are they made of steel and if so, is there any problem with rust?A:
I believe the adapters are necessary to avoid damaging the intake boot. You can clamp a TM40 into the intake boot by squeezing the boot down tight with a hose clamp but I have seen this done on other bikes and eventually the boot will tear along the edge of the clamp. Torn boot = vacuum leak. The intake boot is very difficult to replace because Suzuki holds it on with phillips head screws and those screws are secured with locktite.
Our original idea was to ship the carburetor with a new boot that fit the TM40 perfectly. Then I realized the trouble folks would have had trying to get the screws out and decided to use the adapters.
I purchased a TM40 kit from you awhile back and I'm trying to fine tune it, but before I do I figured I should seek someone more qualified before I just start guessing. My average MPG is about 42-43. I just put on an older model DR Dakar fairing and it bumped it up to about 45 mpg. Any advice on where I should start to improve that into say the 50+ mpg range? I know here in Oklahoma the wind has been ferocious lately and that affects mpgs, but the bike seems like it's chugging down the gas, I'm guessing too rich maybe? I know it's hard to tell without actually riding it, but if there is any information that I can give you for extra help please let me know. The setup on the carb is the same as yours (that I do know). I didn't know if I need to adjust the air screw (if so which way?). Sorry for the drawn out message, just trying to get over that 50+ mpg mark for my TAT trip later this summer! Thanks for your help and selling some amazing products!A:
The first place to start is to drop the needle one notch (raise the clip). Take it for a nice long test ride and pay special attention to how it responds to small throttle movements in the 35-45 mph range. If the drivability is fine drop the needle (raise the clip) one more notch or if that puts you on the top notch move the nylon washer from below the clip to above the clip. Repeat the test ride and repeat lowering the needle. At some point the needle setting will be lean enough to cause surging in that 35-45 mph range. You want the needle setting to be rich enough to eliminate the surging.
If you are still using the OEM Suzuki air filter you might consider replacing it with the Twin Air filter. The aftermarket filter will lean things out just a tad.
Thanks for the kind words! Glad you like our products.
I know this is probably a dumb question, but I'm interested in the TM40 carburetor kit. I've read all of the threads that I can find on this subject but still haven't quite found the answer I am looking for. My current setup on my 2001 DR650 is stock exhaust and a Uni air filter with the backfire screen removed. I like the bike quiet. I understand that the throttle response is much better with the TM40, but I'm not real hard on the bike and pretty easy with the throttle. With all of that out of the way, will the TM40 kit help my gas mileage?
This is the area that I would like to improve on now. Also, I don't know a lot about carbs and jetting, do I need to change anything if I were to purchase this kit from you guys with the setup I have now? Not sure how you guys set up the carbs before they leave, if you do at all. I've seen different prices on these carbs, but yours sounds and looks more like a whole kit, correct?A:
I have been able to get better fuel economy with the TM40 but the improvement is small. In relatively sedate riding with the stock carb I would get 50-52 mpg and with the TM in its current tune I have gotten nearly 56 mpg - pretty good but it would take a LOT of riding to pay back the cost of the carb kit. I don't yet have data on how it compared in more aggressive riding.
I am with you 100% on keeping the bike quiet. My setup is stock airbox w/no snorkel and stock muffler. I did remove the anti-backfire screen but it makes no difference in airflow unless the airbox is opened up. I'm running the K&N filter but our testing shows the same jetting works with the Twin Air filter.
Whenever possible we ship our carb kits set up as close as possible for the buyers modifications. I could certainly send one to you set up identical to mine.
We sell this as a complete kit for the DR650 including throttle cables, adapter sleeves, extra jetting and installation & tuning manuals for $449. We also sell the TM40 by itself for $319 for those folks who can and want to do their own fitting and tuning.
I’m looking for a moderate power increase but don't want to sacrifice reliability/mpg too much. I'm afraid if I go to a larger carb, I'll suffer on the MPG side of things. I do have a pretty conservative right hand, but would really like some more power (who doesn't like to play, right?).
I am getting around 120 miles to reserve stock and would like to keep it above 100 after modifications, if possible. I don't really want to add an aftermarket tank as the extra fuel would only add more lbs to the bike, which I would like to avoid like the plague. I do about 65/35 street/dirt and I just want a little something more out of the bike.
What supporting mods do you have for your TM40? And what mpg do you get? I'm weighing my options here.A:
Proper jetting will not result in more fuel consumption. The reason you hear of people losing mileage after rejetting is because it is easy to jet too rich but more difficult to jet 'spot on'. The TM40 isn't any bigger than the stock BST40 - they are both 40mm carburetors. The TM40 doesn't really make any more power (though it does feel like it).
What you get with the pumper carb is instant and controllable throttle response. On my own bike I actually gained 1-2 mpg with the TM40 over the stocker. The reason for this is you don't have to compromise the jetting setup as much as you do with the stocker. The TM40 can be set to run on the lean edge of good running at cruising speed but still give the necessary squirt of fuel for good response.
I typically average around 52 mpg. The best I've seen is 57 and very enthusiastic riding will get my down to 46-47. I am currently running a modified airbox, K&N air filter and full FMF system with Q4 muffler.
I recently ran out of gas at 170 miles on my DR650 equipped with an IMS 4.9 gallon model. I am currently running a DynoJet kit with the needle in the 4th position, a 160 main jet and the fuel screw turned out 1 full turn. The airbox has been modified slightly for better flow and I have a FMF muffler on it. What can I do to get more mileage and lengthen the distance between fuel stops? If I raise the clip on my needle, will the mileage get better?A:
Careful jetting can yield from 45 mpg up to the low 50’s, and some riders have been known to do even better. Riding at an enthusiastic pace, my DR650 gets between 49 and 51 mpg with my FMF Q4. If I really twist the throttle hard, it will drop down to 45 to 46 mpg which is still enough to get 190 miles out of my IMS 4.9 gallon tank before switching over to reserve. Just lowering the jet needle may improve your mileage, but watch your throttle response as going too far will cause it to suffer. If that happens, go back a notch.
I just got back from a ride and at 63 miles I had to switch to reserve. I went back to town and filled up 1.6 gallons, with a total of 68 miles. I calculated the mileage at 42.5 mpg, does that sound about right for you DR350 owners out there? I just got the bike and I know the air box has been opened up, it has a SuperTrapp exhaust, and has been rejetted. I was thinking I would get more like 50+ mpg from this bike. So I guess my question is does 42 mpg sound about right for this bike?A:
Jetting is too rich. You should be seeing around 50 mpg even with some spirited riding. The first thing I would do is lower the needle (raise the clip) and see how it works.
Anybody know why my gas mileage drops from 54 MPG in the summer to about 48 MPG in the winter with no change in driving habits, etc.? I believe it is due to "winter gas mixture" - which some folks suggested. Sure enough, in the months of Dec - Mar, I get around 48 MPG. During the "summer" months I creep up to 52-54 MPG.A:
It might not be just the 'winter' gas. I believe that the generally colder temps could have an effect on fuel mileage also. My wife has a Prius and its fuel economy is drastically effected by winter temperatures.
Should I go with the DynoJet jet kit or spring for a TM40 carburetor for my 1991 DR650. My concern is that I have heard the TM40 pumper carburetor is not as forgiving to huge changes in altitude as the vacuum operated carburetor.A:
While this is theoretically true it is not necessarily the case. My ride last weekend took me from 400 ft. elevation here at home up to 9550 ft. at the top of the Steens Mountains. The TM40 worked flawlessly the whole way. Yeah, the bike was down on power way up there in the thin air, but there were no hiccups or blubbering at any time. It ran like a top.
I remember reading a few years back (when someone else was putting a FCR on something) that a CV carb was better at dealing with altitude? Like riding from sea level up to 8000 feet. Is this true?A:
I would attribute this to the fact that the OEM standard jetting in most CV carbs is borderline lean to start with. Start out too lean at sea level, jetting will be pretty close at say 4-5000 feet and only a little on the rich side at 8000 feet. Jet your flatslide the same way and you would have similar results. I have ridden my DR650 equipped with the TM40 from sea level to over 10,000 feet with no adverse affects.
Can you explain the differences between the ProCycle jet kit and the DynoJet kit?A:
We created the ProCycle jet kit because the DynoJet kit left so many questions about the installation. Our kit includes much more thorough instructions and the same needle profile as the DynoJet kit, a drill bis (for removing the mixture screw plug), an extended mixture screw, new stainless allen head screws for the bowl and cap as well as the necessary jets. The jets in our kit use the Mikuni numbering sequence (same as stock) to make changing jets now and later less confusing. (The DynoJet jets are numbered on their own scale and it can be very confusing when changing jets.)
I have read on some forums that the DynoJet installation instructions are not correct, is this true? If it is true, what specifically is wrong with the instructions and what should be done?A:
There is nothing really wrong with the DynoJet installation instructions. Like most aftermarket jet kits, DynoJet errs on the rich side to be safe. When following their directions you must remember that their recommended setup is nothing more than a good starting point. You will need to adjust for your particular bike, location and conditions. The DynoJet instructions can be confusing to some users and that is why we developed the ProCycle jet kit. Our own jet kit has much more thorough instructions and diagrams to eliminate as much confusion as possible. We also include all the necessary parts such as the needle jet (same profile as the DynoJet kit), main jets (numbered like regular Mikuni jets), drill bit, an extended fuel screw and new stainless steel screws for the bowl and cap.
What are your thoughts on the Factory Pro carburetor kit compared to the Dynojet kit? I have a TM40 on mine and rode a buddies with the Factory Pro kit and I was very surprised! It had almost the same grunt mid-range to top end, but not as much at lower revs.A:
The Factory Pro jet kit is calibrated to only work properly with an un-modified airbox. They certainly make the bike run very well but if you want to uncork the intake so it can breath and make a little more power, you won't be able to get the Factory Pro jet kit set-up correctly. This kit is only appropriate for riders who will not be opening up the airbox.
I am planning on purchasing a used DR650 and plan to keep the engine bone stock. Will I need to get a bigger pilot jet like on every other bike I have owned?A:
Nope. The DR650 is the exception. Leave the stock pilot jet but definitely remove the brass plug and adjust the mixture screw. To make adjustments really simple, install an extended fuel screw. Below are directions on how how to correctly adjust the fuel mixture.
How do I know if my fuel screw is adjusted correctly?A:
A good place to start is with the fuel screw approximately 2 turns out from lightly bottomed. Use a small screwdriver to gently turn the screw all the way in until it lightly bottoms out, then slowly unscrew it two turns. That should be close enough that you can start the motorcycle easily.
Warm the bike up thoroughly by going for a ride for at least 10 minutes. Once back home, leave the bike idling. CAUTION: Wear gloves for this next part so you don’t burn your hands on the cylinder! Keep track of the number of turns out you have to turn the screw (remember, you started at two turns out) until you just start to hear the idle speed drop ever so slightly. If you are more than 3 turns out from bottom, you may need a larger pilot jet.
Once you hear the idle drop slightly while unscrewing the fuel mixture screw, turn it back in slowly until you again hear the idle start to fall slightly. The second you hear the idle drop, stop and unscrew the fuel mixture screw just a bit until the idle goes back to normal. This is where you want it set. You should be in the 1-1/2 to 2 turns out range. If you are less than one turn out, you may need a smaller pilot jet.
When you finish the work, your idle will probably need to be reset to the factory recommended RPM.
I am new to this whole DR jetting thing, I have always ridden a bike with FI and have never paid attention to the plugs before. Can someone tell me how the spark plugs from my DR650 should look? The bike runs well, starts easy and idles well. It has been cold enough here that I haven't been able to tell how hot it wants to run. But from what I can find the color of the plug makes me think I might be running lean.A:
Modern fuel burns so much cleaner than the fuels of yesteryear that plug color doesn't mean that much. If it runs well don't worry about it.
Does removing the fire screen in the air filter gain me any additional horsepower?A:
In all of our dyno testing, we have never found any performance gain by removing the screen. Removing this screen could make your machine more susceptible to fire and we recommend leaving it in place.
OK, so I want to put the K&N air filter on my bike. Everything is stock and I want to do the filter and maybe a SuperTrapp eventually. But if I start out with just getting the K&N filter do I have to worry about re-jetting the carburetor? I know I will when I get the exhaust but I'm wondering if I can just do the air filter for now without touching anything else. Second question, if I do just the air filter what would it do for performance?A:
No re-jetting will be required unless you also modify the airbox.
I put in a K&N air filter a year or two back when I did a bunch of modifications. Now I want to go back to a foam filter, but when I removed the K&N and went to install the new non-OEM filter, I realized two things: first, I no longer have the filter cage, so I need to get that. Second, there's a thick sponge/foam gasket that goes around the airbox opening, obviously to create an airtight seal for the K&N. My question is, did this sponge/foam gasket come with the K&N and is it required (or desired) when I switch back to the foam filter?A:
The foam gasket came with the K&N filter. It isn't necessary with foam filter but it won't hurt to leave it in there either.
I haven't used the actual No-Toil filters, but I use the No-Toil cleaner and oil on my Twin Air filters. It is great stuff. Seems to work as good as any oil I have used on filters but comes off easy in the cleaner it comes with.A:
The No-Toil oil is designed to work specifically with their filters. Using it on Twin-Air, or other foam filters, will eventually disintegrate the filters as they are not designed to use it. The first thing to go is the glue that holds the filter together. Keep an eye on the condition of your Twin Air.
I just replaced my stock filter with a new Twin-Air filter and was wondering if I need to make any jetting changes because of the swap?A:
As long as you just replaced the filter and did not make any other modifications to the airbox or anything, the stock jetting will be just fine. The same goes for the K&N and No-Toil filters as well. Just swapping out the filter will not require any jetting changes.
I received the TM40 kit today and everything looks good. Would you recommend that I lube the new throttle cables before they are installed, or leave them nice and shiny, but apparently un-lubed?A:
The steel inner cables run in nylon liners so no additional lubrication should be needed, but if you want to lube them use some dry graphite type lubricant. The kind that is sold for locks. Putting oil based lube in cables works nicely at first but the oil attracts dust and dirt and eventually can do more harm than good.
Hey guys, I have a 2005 DR650 that I have put a TM40 carburetor on. It also has a FMFQ4 exhaust on it and I have done the air box modification. At first the thing would make the header glow bright red and you couldn’t throw your leg over it. Went up one size on idle jet and it has cooled down.
My question is, what should a DR650 head temp be running at? I hooked up my Vapor temp to the outside spark plug and was getting temperatures from 280 degrees up to 350 degrees in short order. Running with air flowing was pretty regular 280 degrees or so. Time it took to get off the bike and raise the garage door up to 350 degrees. Is this too much on a bike like the DR, or is this good. It does feel hot from the rider’s perspective.A:
Those temps are nothing to worry about. The head temp will vary quite a bit with speed and load. I wouldn’t be concerned about anything under 400 degrees. Even temps over 400 degrees are fine for short periods of time. The Vapor unit is a great way to keep an eye on your engine temperature.
Thanks for the info, but now I really have a dumb question for you. Could you describe how this surging would feel? I do have a Twin-Air filter in with the stock exhaust and snorkel removed. I think it runs ok, but would just like to see those mpg's up. And I totally understand that it is a process and I do want to learn it, it's just getting to that point. Thank you again for all of your help with this. I didn't know if this was something I should post on Thumper Talk or not, I know they're picky about products on their boards.A:
Surging is experienced when riding. You are trying to maintain a steady speed, the bike will minutely speed up and slow down or you may find yourself having to constantly adjust the throttle to keep a steady speed. It's likely to be kind of subtle.
I live in Sydney, Australia and have a 1998 model DR650. I have fitted 17" motard rims to it and am looking to convert it to a full-blown Super Moto bike. Here are my questions:
- Does the Mikuni carburetor make much of a power difference?
- Will this help to cure all the flat spots? Is it smoother with it?
- Will I still need to get it re-tuned to suit my Yoshimura pipe (which was off a gsxr1000)?
- Are the intimidators better than the emulators? If so can I fit the intimidators into my forks and get away with that or is it advisable to change the springs to suit. Are the spring ratings that you have the SM specifications?
- I am 110 kg, do I need to re-valve the rear shock to a more suitable spring? I have been advised that I need a 9.5 rear spring rate for my weight. I think yours is 8.5 is that suitable for my weight.
- Is the fork brace worth it?
As you can see I am considering the Mikuni carburetor and the suspension modifications front and rear. Do all parts come with full instructions? What is the shipping costs and how long for delivery?A:
Here are your answers.
- The Mikuni TM40 is a huge improvement over the stock carburetor.
- It gives instant throttle response and runs much smoother down lower in the RPM.
- We can ship it jetted for your particular bike setup.
- I don't have any firsthand experience with the Intimidators. I have installed the Race Tech emulators in lots of bikes and I think they are a great product. I would definitely recommend upgrading the fork springs.
- You rear shock will definitely need to be rebuilt and have the oil replaced and a Race Tech Gold Valve installed. We sell a kit that includes the Spring, Gold Valve and Oil along with detailed instructions. You may also want to order a Shock Seal Head Kit to make your rebuilt top-notch. The stock shock is not even adequate for a 50 kilo rider. With a good re-valve you should be fine with our 7.5 spring. I don't know who recommended a 9.5 rear spring. It would be way to stiff unless you were riding 2-up with a ton of gear. I don't even know of any company making a 9.5 spring that would fit the rear of the DR650.
- The fork brace is a nice improvement. Especially for a motard that will spend most of its riding on pavement.
Shipping to Australia typically takes a week. Shipping cost is based on weight and springs are heavy. Depending on exactly what all you order shipping will likely come in around $70-$90.
I was browsing your web page trying to sort out what I should consider for a 2009 DR650. So I have a few questions that maybe you can answer for me:
- I was trying to decide between the big bore or the complete kit of the high compression w/cam. What is the difference in power / performance between the two? Or, am I comparing apples to oranges to some degree. Should I be thinking of the big bore vs. the high compression, and figure the cam should be used for either?
- Also, should I assume that I need to upgrade the carburetor and exhaust as well for both these upgrade routes?
- Lastly, for a carburetor, I need to sort out whether I should go with the Mikuni TM40 pumper upgrade or try to go with the Keihin FCR-MX? How does the Mikuni perform vs. the Keihin?
It is somewhat a case of apples and oranges.
- The high compression piston and cam kit will give you crisper engine response and a motor that is more willing to rev and makes more power everywhere with a better top end pull. The big bore 725 kit by itself will give you a motor with a powerband similar to stock but with the biggest gains mostly in the low end and mid-range. For the best of both worlds add the cam to the 725 kit.
- Upgrading the exhaust and carburetor are not required but will definitely help make the most of the engine modifications.
- Performance wise, the TM40 and FCR are nearly equal. The TM40 will flow slightly more air so might have a small power advantage in a well built and tuned motor.
The choice between TM40 and FCR comes down to what is practical for you. Our TM40 kits are a 'plug and play' setup. New carb, jetted for your bike. No tinkering necessary. Most people setting up an FCR will start with a used carb from a Yamaha YFZ450 ATV and have to make their own modifications to make it work. IF you can find a GOOD used carb and get it for a good price the FCR can be done for less money than our TM40 kits. At this point there isn't anyone offering brand new FCR carbs kitted up for the DR650. New FCRs are very expensive. One technical advantage to the FCR is the air cut valve that decreases decal popping noise from the exhaust. Both the stock carb and the TM40 will cause popping noise from the exhaust during deceleration with closed throttle.
I found out why the valve cover gasket was leaking so bad, the gasket had a huge section gone! The top end looks brand new and the timing chain looks brand new. When I put this back in, what are the clearances supposed to be on the valves?A:
Don't put that gasket back in! There should be no gasket between the head and the cam cover! You should only use a sealant (like Yamabond). I'm guessing the last person that worked on this did not know that and hand-made a gasket for it.