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to stroke or not to stroke

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I am considering getting the 250 stroked by Powroll bringing it to 291cc. It is already bored to to 277 with a weisco piston.

Does anyone have any experience with putting a stroked crank in the 250? Thoughts?

Also, how hard is it to get the crank out? will I need any special tools? I have the Honda Service manual.

Thanks

John

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no comments? Has no one had experience putting a stroker on there xr?

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I havent done it personally but it should give you a good boost in torque and a couple more ponies. Try it and get back to us.

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I am considering getting the 250 stroked by Powroll bringing it to 291cc. It is already bored to to 277 with a weisco piston.

Does anyone have any experience with putting a stroked crank in the 250? Thoughts?

Also, how hard is it to get the crank out? will I need any special tools? I have the Honda Service manual.

Thanks

John

John,

just talk to Rob Barnum at Barnums Pro Products where ya got yer carb at he will be more than happy to walk you thru it :)

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John,

Dwight Rudder has built a bored and stroked 300. Do a search in this forum using the term stroked.

I'm considering doing the same thing, but I'll have to wait until June.

Looking at the Powroll web site you can get the parts for under $600. But you still need to find a shop to bore the cylinder.

Good luck on your project.

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I am currently looking at purchasing a new XR250 and "building it" - I have built several before and do know that sometimes "more is less". I stay away from cams, high compression pistons and stroker kits...

I talked to a friend who is a honda factory trained tech who has built honda XRs for many years.. He says don't stroke - points he made to me were...

1. In '86 they went to a longer stroke from the previous year. This is the longest stroke that the engine can reliably maintain and the longest stroke that will provide optimal horsepower.

2. A longer stroke in the given configuration will provide torque and increased "hit" off of the bottom but will dramatically decrease top end power and "rev-ability" of the motor. It will yank and sign off quickly and won't be fast (although seat of the pants might tell you that it is...)

3. In stroking the motor - they shorten the rod and relocate the lower pin on the crank. This results in "egg-ing" of the bore. The piston skirt must be shortened and the shorter rod puts side loads on the cylinder walls - the piston is pushed sideways into the cylinder... Engine longevity is not good.

------------

Right now, I am on the fence between the thumper 80mm piston (custom made for thumper by wiseco) or using the 77-78 mm J & E piston. The difference between the two is compression - the 80mm piston is 10:1 compression (10.2 was stock for pre-96 motor). This provides reliability and lets engine rev into upper rpms well. The J & E piston uses 10.5 : 1 compression (stock compression for post-96 motor) and will provide a little more torque and "grunt" off the bottom (and I won't have to sleeve the cylinder).

If I go with the 80mm piston - I will go with northwest sleeve for the 300cc sleeve. Based on motor smoking and oil analysis using thumper racing sleeves - I believe northwest sleeve uses higher quality iron for their sleeves.

Carburetion will be with 35mm keihin FCR. I believe it is far superior to the edelbrock that many here rave about. The keihin (even the stock keihin) does more to aerate and atomize the fuel prior to it even entering the bore of the carb. The result is better throttle response, efficiency and hp.

Back to your situation. If I were you, I would swap out the wiseco for a J & E (they are lighter than off the shelf wiseco) or go with thumper 300cc piston. Take the money you would have spent on the stroker kit and spend it on a Keihin FCR.

Or just step back and do one thing at a time. Next step would be keihin fcr.

- jeff

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