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The DR900 - DR650 Big Bore Stroker buildup

This idea has been sitting on the back burner for a long while now. I finally have enough time and space to get on with it.
2 Years ago I had a Crankworks build a 10mm over stroked DR650 crank. Carrillo made up a special 5mm shorter rod which cost a bundle but makes the longer stroke crank fit within the DR motor without a bunch of difficult modifications.
Here's the crank:

The Carrillo rod is a thing of beauty.


I have collected a few organ donor DR motors.
On the left is a high mileage 1996 missing the top end. It's got good center cases. The other 2 motors are 1998s with broken crankcases because of the lack of a torque limiter in the starter drive. :sad:


I'll combine the best parts from these three motors for the DR-zilla. I've also got a 790 piston, cylinder and 190 cam set aside for the project. The final displacement will come to 886cc. :crazy:
The biggest unknown I see is what to do with the clutch. I'll almost certainly have to come up with a way to add additional plates to the clutch pack.
No, sorry, this is not ever going to be a kit :s_cool
Folks are really interested when they think they could buy a kit for a few hundred bucks. The fact is that a 900 kit would have to sell for at least $3000. That would be just a kit, no labor, no cam, no 3rd gear upgrade or any of the other things you would probably want to add at the same time. No, this is not a commercially viable project. It's just something I've chosen to do to push the envelope and learn about what is possible. If it doesn't explode on the first ride and someone else is crazy enough to want to build their own stroker I'll be happy to help point them in the right direction.


Engine builds always get held up by something. My first holdup was getting all new bearings for inside the crankcase. The crankcase donor had around 50K miles so reusing the old bearings was not an option. Note the billet 3rd gear set. I'm sure there will be more internal parts needed but you never can tell until everything is apart and inspected.


So, armed with new bearings it is time to start tearing the motor down. It's easiest to start on the left side and remove the stator cover, shift linkage, starter drive and flywheel.


Everything from the left side stays together, gets cleaned up together, gets boxed up together. This eliminates the possibility of getting bolts, dowel pins, thrust washers, etc getting mixed up with other motor parts.
See the broken stator cover? That's crash damage that ended the useful life of this bike. Luckily I have good stator covers from the other donor motors.


Same thing happens on the clutch side. I'll pull the clutch stuff from a different motor because the first one has already been pillaged for clutch parts and I want to make sure I don't miss something.


Again, everything from the right side stays together through the whole process.
The neutral safety switch screws were only finger tight just as expected.

Since the top end was already removed from this donor some time back it's time to split the cases.
I made a case pulling tool out of a piece of half inch plate.
The case is held tightly by the press fit of the left crank bearing. The tool pushes the crankshaft out of the left case half and separates the cases in the process.


The left case half lifts off leaving all the internals in place in the right case half.


Here are the cases cleaned up and with the old bearings removed.
Heat makes removing the bearings really easy. I put the cases open side down in the shop oven and turn it up to 350 degrees. Come back in 25 minutes and all the bearings have fallen right out.

After getting the case halves clean I followed up by blasting them with walnut shells, masking off and painting the outside with high heat satin finish black. Walnut shells aren't abrasive enough to harm any of the machined surfaces like sand would. Glass bead blasting is a big no no because the glass will embed into the aluminum and end up inside the motor. Walnut shells are easy to thoroughly clean off too. Heat is just as useful putting the bearings is as it was taking them out. With the cases heated to 350 degrees to cure the paint it was simple to just drop the bearings into their bores.
Yay! It's always a good feeling when the project turns the corner and parts start going back together instead of coming apart.

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