Gearbox bearings

[JIM77]

I've just started putting my 96 cr250 engine back together and one of the gear box bearings on the right case is loose, and hasn't developed an interference fit. It's the bearing for the main shaft.

There's no signs of damage or wear on the bearing seat and I'm using OEM bearings, I can't find any reference in my clymer manual, is it possible it's meant to be this way?

If not, can anyone recommend a fix?

[alexbrown64]

Jim, we have just been discussing the same thing here: http://forum.ozvmx.com/index.php?topic=36759.0;all
I have the same problem with my mains for an 83 YZ125.  Just organizing another set of cases from the US but there are folk who can machine your case and fit a sleeve if necessary.  I believe you should have an interference fit otherwise your bearing will just spin in the case.  I was also looking at 620 green bearing loctite. 
Cheers,
Alex

[JIM77]

It's weird because all other bearing are pretty snug, even with heating the case and freezing the bearings, they all pretty much needed some persuasion, except the ones with retainers. So the cases are pretty good condition generally and I don't think the motor has done much work for its age.

I be interested to know how well the loctite works for the long term though, it looks pretty good and I'm only talking a fly shit of interference required.

[alexbrown64]

Hey Jim, here is a great link to an engine rebuild for the 92-01 CR engine.  Perhaps you can rip one of the pics out of it, highlight what bearing it is and post it up. Someone on here is bound to know more about it.  Green loctite, retainers,  OEM bearing etc, im sure there is a simple solution..  anyway, check out this link as im sure it will help in your rebuild..
http://www.allthingsmoto.com/forums/f-14/92-01-honda-cr250-engine-build-tutorial-64413/
Cheers,
Alex

[pancho]

I've just started putting my 96 cr250 engine back together and one of the gear box bearings on the right case is loose, and hasn't developed an interference fit. It's the bearing for the main shaft.

There's no signs of damage or wear on the bearing seat and I'm using OEM bearings, I can't find any reference in my clymer manual, is it possible it's meant to be this way?

If not, can anyone recommend a fix?

It is Quite possible that this is a design feature, where the bearing is designed to re-align itself as the cases expand and  contract with temperature change. (Cold engine-Hot engine) The other end of the shaft/bearing assembly is often securely mounted with a retaining plate on the track and a strong circlip on the shaft. Other than that if the bearing is a bit too loose loctite bearing mount does the trick. cheers pancho.

[JIM77]

Hey Jim, here is a great link to an engine rebuild for the 92-01 CR engine.  Perhaps you can rip one of the pics out of it, highlight what bearing it is and post it up. Someone on here is bound to know more about it.  Green loctite, retainers,  OEM bearing etc, im sure there is a simple solution..  anyway, check out this link as im sure it will help in your rebuild..
http://www.allthingsmoto.com/forums/f-14/92-01-honda-cr250-engine-build-tutorial-64413/
Cheers,
Alex

Yeah mate, I've been all over these threads on ATM, the bloke who wrote them is a wizz with these Cr250 engines. I tried contacting him to get is opinion, but haven't heard anything back yet. Will get some photos posted and see what you more experienced blokes reckon.

Thanks Jim.

[JIM77]

I've just started putting my 96 cr250 engine back together and one of the gear box bearings on the right case is loose, and hasn't developed an interference fit. It's the bearing for the main shaft.

There's no signs of damage or wear on the bearing seat and I'm using OEM bearings, I can't find any reference in my clymer manual, is it possible it's meant to be this way?

If not, can anyone recommend a fix?

It is Quite possible that this is a design feature, where the bearing is designed to re-align itself as the cases expand and  contract with temperature change. (Cold engine-Hot engine) The other end of the shaft/bearing assembly is often securely mounted with a retaining plate on the track and a strong circlip on the shaft. Other than that if the bearing is a bit too loose loctite bearing mount does the trick. cheers pancho.

I'm thinking this could be a reasonable explanation, the only problem I can see is on assembly of the bottom end the, gear box is assembled from the left side case and holding the said bearing in place will be a PITA.

I Know some of the bearings fell straight out of the case when heated on disassembly, should have paid more attention at the time though, to which ones. Admittedly I did take the engine apart almost a year ago now, so that's a bit of challenge in itself.

[JIM77]

Photos attached, the culprit is the top right in the first photo. I got I wrong too, the gear box needs to be assembled from this side of the case, so the bearing will stay put. Opinions please? Loctite and be done with it? The bearing seat is in good condition as you can see by the other photo.

[Nathan S]

https://www.facebook.com/groups/628913867217054/?pnref=lhc

[Momus]

Use some Loctite 620 'Cylindrical retaining compound'.

This stuff has about 4000 psi shear strength- so with probably 2 square inches of surface area on the crook housing the bearing will stay put- and it is good for 450 F.

It  has saved my arse on various race car bearing mountings- gearbox extension housing bushes and on aluminium hubs.
If it is mistakenly used on studs or bolts into aluminium castings it is so strong that the female threads can be torn out.


.

[JIM77]

Thanks for all the advice, I've convinced myself that the loctite 620 is the most practical answer and grabbed a bottle today. I wouldn't go that option if it was a main bearing etc, and given that the seat is only a fly shit worn, she'll be right.