Gearbox Bearings Install

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AltaNorton

AltaNorton

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I'm putting new bearings into my gearbox, I have heated the cases and put the bearings in the freezer, but I'm still having trouble getting them in. I've been using sockets as drifts but don't have a press so getting them in is quite a challenge. What methods have you used?

Also, the layshaft bearing is flush with the case, but I can see that it is not all the way pressed into the bottom of it's cavity. It doesn't want to go in any further and I don't want to ruin it. It is supposed to go all the way to the bottom isn't it?

Thanks
 
At 300 to 350 F. the bearings will fall into place it they are straight and have a little oil on them. No drifting or freezing should be required. Jim
 
Alright thanks. The cases were up to 325 but I didn't put any oil around them I'll try that and make sure they are perfectly straight. As for the superblend layshaft bearing, it's stuck in there and I think the only way to get it out will be to heat the cases but will that ruin the bearing if there's too much heat?
 
mattthomas4444 said:
I've been using sockets as drifts but don't have a press so getting them in is quite a challenge. What methods have you used?
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If the case is hot enough, then the cooled bearings should "drop" in? There shouldn't be any need for drifts and certainly not a press.

Presumably you are fitting a layshaft roller bearing-so you will already have fitted the inner race to the layshaft? Fit the outer part of the bearing over the inner part and use the layshaft as the fitting tool, but speed is important, the quicker you get the bearing home the less chance it has to expand.

Same with the sleeve gear bearing, fit the bearing onto the sleeve gear first, then fit the mainshaft into the sleeve gear and fit the sleeve gear with bearing into position with the mainshaft.


mattthomas4444 said:
Also, the layshaft bearing is flush with the case, but I can see that it is not all the way pressed into the bottom of it's cavity. It doesn't want to go in any further and I don't want to ruin it. It is supposed to go all the way to the bottom isn't it?
Click to expand...

If it's flush with the case then it's probably in all the way in.
 
There is a space behind the layshaft so if needed you can get a bearing puller in there. Flush should be good.

Dave
69S
 
Thanks LAB I'll bet that putting the bearings on the shafts will help.

Dave, right now the bearing is in the bore and flush with the surface of the case, are you saying it doesn't need to go any deeper? Also I will probably take it out anyway just to put it in with the shaft to make sure it's perfectly straight. Can the bearings shield take high heat without damage or should I try taking it out with out heat?
 
If you run your finger around where the bearing and shell meet nearest you, you should be able to feel if the bearing is in straight or not. You might be able to get a small straight edge on it too. I'm not the expert, but I do know that there is space below the bearing to get a puller in there, I did it on mine and another, they just would not fall out. Yes, when you put the gearbox bearings in, best to put them in with the case hot as possible and on the end of the shaft they run on. Helps get things lined up. I used a small gas grill outside to do it.

If the shields are bronze, fine, don't know about the plastic or polymer ones, they probably won't take the heat. I remember reading that makes them a one time bearing.

Dave
69S
 
A polymer bearing will take 300 to 350 degrees easily. A buna rubber sealed bearing will not.
I was taught that when installing a bearing in an aluminum housing it was best to heat the bearing a little and the housing a lot. A steel bearing changes very little in size with temperature change but it will hold a lot of thermal energy and will draw the heat from the aluminum rapidly causing problems. I was always taught that freezing one part and heating the other was only used when shrink fitting like metals.
So that is how I always have done it. Jim
 
Well, I got all of the bearings seated just right. Thanks for the help, I did freeze the bearings overnight, and I think the reason they didn't pop in the first time is due to the fact that the cases were not hot enough. The large main bearing just dropped right in and the others were easily pushed in with the shafts attached, plus a little oil.

Thanks,
Matt
 
Good, now tell us the truth....how many times did you say mother f***er during the process? I think I was up to about 40 times per minute before I got my bearings to seat properly!

Russ
 
I rebuilt two Commando gearboxes last winter (the one from my bike, and a "spare") and found that 275* F works just fine. 250* F did not, so that last 25 F* was the ticket. Can't see why you'd ever need to go hotter. FWIW/YMMV
 
That layshaft bearing can be a little tricky. I ruined one when I apparently did not have the case hot enough. The bearing went in crooked, got stuck, and I ruined it trying to get it out. The plastic cage popped out and the rollers went flying. I had to buy a new bearing. I sent the parts to Jim Comstock and had him install it. He could probably do that job in his sleep!

Mick Hemmings makes it look so easy in that video... :?

Debby
 
This certainly is a confidence breaker. I dread doing this job and am dreading it more post by post.
 
If it's any help, I didn't have any trouble. I used Hemmings ball bearing, so no shimming.

Dave
69S
 
britbike220 said:
This certainly is a confidence breaker. I dread doing this job and am dreading it more post by post.
Click to expand...
Same as you.Nothing to do but to do it if you know what I mean.
 
Yeah, go for it! Builds character, whether you succeed or fail. :D

I think my problem was just that I needed to get the case a little hotter. I only heated it to something like 200 degrees. Not quite enough. Next time I'll set the oven at 300. 8)

Debby
 
BrianK said:
I rebuilt two Commando gearboxes last winter (the one from my bike, and a "spare") and found that 275* F works just fine. 250* F did not, so that last 25 F* was the ticket. Can't see why you'd ever need to go hotter. FWIW/YMMV
Click to expand...


Probably wouldn't need to go hotter if everything goes right. But the aluminum temper is not affected until the temp exceeds 375 degrees so heating to between 300 and 350 gives a little margin for error. You would want to be careful if your using a torch to heat it that hot because you could sure make hot spots that could cause damage. Jim
 
The spit test works on this casing (as with others). If spit balls and fizzles then it's hot enough.

I prefer to do it with a pair of thin leather gloves on just to reduce the attraction of knuckle to hot surface.
 
Well my swearing was kept to a minimum since I managed to do it in the kitchen with my mom and dad in the house ( I cant believe she let me). but there was a time when i though my mechaninc touch had magically been reduced to that of a infant. Now lets hope the rest of the gearbox goes together as easily as the second attempt with the bearings
 
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