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XR600 crank bearing confusion

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Hi all,

I'm currently rebuilding my 1989 (ish!) XR600 engine. I thought "lets do a proper job and replace all the bearings!" and so begins the woes 👍

It turns out several of the bearings are Honda special varients of industry standard ball race bearings, eg. balance shaft and cam bearing (the one by the sprocket). I have also found out the smaller crank bearing is narrower than the standard 6307 bearing by 3mm, even though the parts list description says 6307!

My question is this: should both the bearings be C3 (thats extra clearence for high speed/temperature running) or is it just the larger one (the 6308)?

Im quietly confident the guys in the machine shop at work can grind 1.5mm off both sides of a standard 6307 bearing to make it fit (they spend all day re-working aircraft fuel system parts so their work is top notch! :smashpc:) and if I stick it through our ultrasonic wash system any swarf will be removed leaving a replica of the Honda special!

My budget has all but disappeared so if I can do this then the pair of bearings will cost £15 instead of nearly £70!

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My question is this: should both the bearings be C3 (thats extra clearence for high speed/temperature running) or is it just the larger one (the 6308)?

I wouldn't know for sure apart from saying I've used just a stock bearing from a bearing shop on one side of the crank and the Honda original on the other..Nothings burnt up as yet..

You're of course correct about some of the others also having to come from Honda,,nothing else fits..

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I still cant work out for the life of me why Honda had to use special varients of standard bearings, it seems un-necessary when some small modifications to the parts could use standard bearings, eg. if both ends of the cam were the same diameter both bearings would be standard :smashpc:

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