Tech Help XR 650 R

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Tech Help XR 650 R

Post  sune on Mon Dec 23, 2013 8:50 am

I'm in the process of rebuilding my XR 650 R motor, all parts including new crank are OEM from Honda. When I assembled the engine casings i noticed that there is about 3mm of flotation on the crank where you can either move the crank to the left or right. This does not seem correct as the tolerances seem to way to high it is almost as if the crank is 3mm to narrow. Is it possible to overpress the bearings too deep onto the crank especially on the side where there is the press fitted balancer shaft gear resulting in the casing bearing being too close together thus causing the flotation.

I would be nice to get some specs of the distance to the outer limit from the one bearing to the outer limit of the bearing racer on the other end of the crank that I can use as a comparrison.

I would also like to highlight that this is a full Honda HRC spec motor that is now being changed back to standard spec and I don't know if this involved any machining to casings to allow for possible larger parts as I noticed that the removed cam, cam gears, timing chain and valve springs are all larger than the standard spec. Unfortunatly I don't have the old crank as comparrison as I have already thrown it away.

And help appreciated
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sune
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XR650R Year : 2004

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crank float

Post  temporary kiwi on Tue Dec 24, 2013 11:05 am

the crank pin should be level/flush with the flywheel on both sides, the flywheel should have at least 12thou gap to the crankcase on the clutch side to allow for swell via heat, 3mm side to side does sound excessive, the conrod has to have clearance for the thrust washers, not sure the exact figure at the moment, possibly the crank has been pressed togeather too much resulting in the extra play

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Re: Tech Help XR 650 R

Post  AURORA on Thu Jan 16, 2014 4:51 am



The Rh bearing sets the play once you tighten the main crank final drive nut on the right hand side

If the main bearing is loose on the LH side on the crank end it will move back and forth or the bearing is worn or bad


Could be a bad crank.
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Re: Tech Help XR 650 R

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