so i split the cases on my 1986 xr600r, and after removing all the bolts and disassembling the external parts and mechanisms, the right side case came right off of the left side case. so the left side case is laying on the bench with the crank still in it, i grabbed onto the crank and it slid right out of the left side case ( after removing the balancer of course). both crank bearings remained on the crank. my question - arent the cranks pressed into the left hand case ?. should the crank and bearings have come out that easily? is it safe to put this crank back in by simply dropping it back into the case/ the bearings are like new! no wear on the bearing outer races or inside the case where the bearings seat! i think somebody before me replaced the crank bearings and never started the bike after replacing them. is there any way to tell if the crank was installed properly before i removed it? thanks dan

Yes they are supposed to be pressed in.

I found the same thing on mine a few years ago. I put my engine back together and ran it until about a month ago. I changed bottom ends for other reasons and I have not yet taken a look at the old one to see what the bearings and cases looked like.

I asked the same questions at the and no one really had much of an answer other than give it a try. Since then I've learned more and I would now use a high temp retaining compound like Locktite 620 on the bearings to hold them in the cases. It's good to 450F and that might just be barely enough. I don't know of any higher temp retaining compound, but that does not mean there isn't one. Something that could take 550F would be better.

I'm pretty sure it's the cases that are the problem. I just can't see how the outer part of the bearing could wear. My theory is extreme overheating anneals the aluminum and that relaxes the metal leading to the loose bearings. The other possibility is metal debris. A bit gets stuck between the ball bearing and the outer race. Suddenly the ball stops turning and the momentum of the moving crank spins the outer bearing race in the case. It would not take much of that to wear the cases so the bearings are no longer tightly held.

If you are going to use a Loctite product to retain the bearing, take a look at Loctite 603. While it does not have as high a temperture tolerance as 620 (300 vs 450), it does a better job curing if oil is present.

Thanks guy ill stop at napa and look into these retaining compounds! I think I'd subscribe to the annealing theory, it makes sense to me!

I've never used these retaining compounds before! I'm just scared to "spin" a bearing! then again I dont wanna buy new cases or used cases and be in the same boat I'm in now.
Cleonard- did u coat the outer race with loctite, or small dabs? How much of this stuff should I use? The bearings fit in the case snugly just not press fit, u can pullem by hand but there's 0 clearence between the bearing and case!

Aren't there steel rings cast into the case halves where the crank bearings go?

Yes there are steel rings cast into the case! What's this mean?

HeadTrauma said:

danduvall said:

It's been too long since I've been into mine. I sure seem to remember steel bearings into aluminum cases. I have a couple of older 80's cases in the garage I'm going to look at tonight.

Are those rings a removeable race of sorts?

If the fit of the bearing into the steel seat is a snug push fit, you probably have no worries. If you decide to use the loctite, make sure that the surfaces are free of oil/grease. Apply a thin coat of the Loctite to the outer surface of the bearing and slip it into the seat. Take a look at the bearing plate that is fitted between the bearing and the steel seat. Sometimes they are beat up a little and need replacement.

creeky said:

The crank gets over 300 for sure. I'd lay even odds that it might get at hot as 450. Using the 620 will require maximum cleanliness for sure. Lots of carb cleaner and then brake cleaner to get as much oil out of there as possible before installing the bearing.

danduvall said:

I've never used it in an engine, but I did use it on my rear hub. I only came across it after I put my engine back together. I didn't even know this stuff existed at the time. I used the high strength 680 to hold the chain side hub bearing on my rear wheel. I coated the bearing and the hole with a thin layer and then assembled everything. The bearing had basically zero clearance, but it would turn just like your crank bearing. It's been holding that bearing just fine for almost a year now. I hope it comes apart when it comes time to replace that bearing.

You don't want extra floating around inside the engine, but you want the whole bearing to case area with retaining compound.

I got home and looked at my cases and there's definitley a steel ring cast into each case half! I'm womdering if thes are replaceable?! On the outside of each case there's 3 holes in each case and they're positioned evenly around the steel rings, like the hole would be used to drive the rings out! I duno! Prolly sounds like I'm grasping at straws! Lol I'd just hate to put this engine together and have something so critical fail!

I remeber reading from xr600 manual ' if bearing comes with
crankshaft - replace the bearing ' maybe the bearing is shot

I would go with a Beer and the big gun

J-B WELD
Part No. 8265-S

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Tensile Strength: 3960
Adhesion: 1800
Flex Strength: 7320
Tensile Lap Shear: 1040
Shrinkage: 0.0%
Resistant to: 500° F
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A: J-B Weld (Part # 8265-S, 8265, and 8280) can withstand a constant temperature of 500 degrees F. The maximum temperature threshold is approximately 600 degrees F for a short term (10 minutes).
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A: When fully cured, J-B Weld can only be removed by grinding or filing it off, or by directly heating the product above the 600 degree maximum temperature threshold.

http://jbweld.net/products/index.php

I love this stuff! I have seen engine cases slow cure epoxy and run for years that cr250 1987 is still going.
just my .02

replace the bearing

JBWeld is great stuff, but I don't think it's the best for this application. It's just way too thick to deal with .001 or less gaps.

It might be worthwhile trying a new bearing. They are not too expensive from a bearing shop.

i don't think u should worry about it, Honda like it on the free side ;)
my XR bearing to case clearance was also like that(not only in the crank shaft).

on the CR engine it's also like that and it was normal.