Layshaft bearing replacement/First Post

Hi all.

This is my first post but I'v been on the site going on 2 or 3 years now and I would first just like to thank all of you for the help fixing up my 73 750 and getting it back on the road in those 3 years. The search function is wonderful, and I'm amazed that it took this long for me to come up with a question that I finally had to post.

After 600 miles of pretty much flawless operation last summer I finally got around to replacing the layshaft bearing. I have searched and read enough posts to the point I finally felt comfortable enough to open up the transmission and try to replace the bearing myself today but I hit a snag, and it's not one that I've read about (or at least I can't remember, so I'm sorry if this has been asked).
To my understanding there will be three ways the bearing will come out. Either the ballbearing will be loose in the case, allowing the layshaft and bearing to be pulled out easily with no heat. Or if a replacement roller bearing was fitted the race will be pulled out on the layshaft leaving the bearing tight in the case. Or the ballbearing will hold the layshaft tight in the case and will require heat and possibly some sort of puller device. Now my question, and probably an easy one for you knowledgeable folks: My Layshaft came out easily with no heat required, but it left the entire ballbearing tight in the case. What does that mean for me and this repair project? Is the end of the layshaft worn and I'll have to get a replacement before I can install the new roller bearing that I have? Is this even an issue since I'll be switching to a roller and shimming the layshaft? The race of the new roller will slide right on the oily layshaft and it will spin but does not seem to be a sloppy fit.

Any help or experience would be greatly appreciated. Thank you.

Hi, welcome. How hard did the shaft resist pulling out?

If there is little or no noticeable play between the shaft an new bearing race and no sign marks damage or worn area on shaft from old bearing then high strength bearing fit may work. Or check that the bearing is correct size tolerance to hold on shaft. Either by measuring if you have access to suitably accurate equipment or consulting with manufacturers specifications.

My layshaft came out of box with no effort (slid out lightly gripped with oily fingers) but the old bearing was very tight and a nightmare to remove needing lots of heat plus a large slide hammer. But the replacement roller bearing race fitted nicely on the shaft with gentle tap.

theocean said:

My Layshaft came out easily with no heat required, but it left the entire ballbearing tight in the case. What does that mean for me and this repair project? Is the end of the layshaft worn and I'll have to get a replacement before I can install the new roller bearing that I have? Is this even an issue since I'll be switching to a roller and shimming the layshaft? The race of the new roller will slide right on the oily layshaft and it will spin but does not seem to be a sloppy fit.

Click to expand...

Clean and dry the shaft end and the ID of the bearing. Then slide the shaft back into the bearing with red locktite.
Then you can use a heatgun around the bearing and get the case nice and hot and use the now glued in place shaft to pull the bearing out.
If that doesn't get it, then you will need to find someone with a automotive clutch pilot bearing puller with a slide hammer to get it out.
The new bearing will probably fit a little tighter, the tight fit is not really critical. Jim

To remove bearing use a suitable sized Ramset Dynabolt ,used for masonry anchoring(available from hardware store).Tighten Dynabolt so its end grips to bearings inside diameter then heat gbox with heat gun and pull on Dynabolt.Bearing should come out attached to end of Dynabolt.Dynabolts also good for removing wheel bearings as gives a surface that can be tapped out with a hammer from the other side so long as bearing is not to be reused as could damage bearing balls/races.

Thank you all for the input.

Concours, as long has i pull the shaft straight out (square) of the old bearing, there is little to no resistence.

Toppy, the shaft does not seem to be all that worn on the end...no more so than any of the other areas on the shaft. I measured it with my cheapy digital calipers and got 16.92 or 16.93 mm. When I measured the ID of the new roller bearing race I got 16.94 or 16.95 mm. Are those figures satisfactory? I believe I bought the roller bearing from CNW, however, it was a few years ago so I could be mis-remembering.

Jim, when you say the tight fit is not really critical I assume you mean the fit between the shaft and the race, correct? And if so, why is that so, when, from my understanding, a tight fit is critical between the bearing and the GB case? Are the metals of the shaft and the race to such a degree of hardness that a little slipping wont do much damage, where a little slipping between the bearing and the soft aluminum of the case would wear the case quickly. Sorry for being redundant, I just don't want to assume I understand all this stuff when I don't...after all that was one of the reasons i got this project was for the learning experience (and it has certainly worked). Would it be benefitial to apply some locktight on the new race when it comes time for assembly or is it unnessary with my measurements from my cheap digital calipers?

I decided to try the red locktite method first, let it cure over night, then give it a try tmrw. Then try the Dynabolt anchor method if no one at my work has a suitable bearing puller. I hate using those anchors for what they are meant for but i can see how they could come in handy for instances like this...I'll definatly put them in the bag of tricks.

As another way to show my gratitude for the friendly people and info on this site I'll try figure out how to upload some before and after pictures one of these days. I bought it from a neighbor who chopper-rized it in the 70's and had it sitting in his garage for the last 20+ years. It's nothing special compared to the machines on this forum but it's mine and has a little of it's own character/patina.

theocean said:

Jim, when you say the tight fit is not really critical I assume you mean the fit between the shaft and the race, correct? And if so, why is that so, when, from my understanding, a tight fit is critical between the bearing and the GB case? Are the metals of the shaft and the race to such a degree of hardness that a little slipping wont do much damage, where a little slipping between the bearing and the soft aluminum of the case would wear the case quickly. Sorry for being redundant, I just don't want to assume I understand all this stuff when I don't...after all that was one of the reasons i got this project was for the learning experience (and it has certainly worked). Would it be benefitial to apply some locktight on the new race when it comes time for assembly or is it unnessary with my measurements from my cheap digital calipers?

I decided to try the red locktite method first, let it cure over night, then give it a try tmrw. Then try the Dynabolt anchor method if no one at my work has a suitable bearing puller. I hate using those anchors for what they are meant for but i can see how they could come in handy for instances like this...I'll definatly put them in the bag of tricks.

Click to expand...

I have just seen several layshafts that were loose enough that the bearing could be pulled of by hand and it never seemed to cause any problem. If a new bearing is not very tight you might want to use a bit of red locktite when you re-assemble it.

The dynabolt method may work. I have also known people who went to their parts store and rented a pilot bearing puller for a few dollars to remove the bearing. Jim

Ok, thanks Jim. One of the reasons for this project was a learning experience, but another reason was to slowly fill my tool box so I can properly use that knowledge on future projects. The search results for a pilot bearing puller didn't seem too expensive so I might just have to shop around a bit and buy one if the locktite doesn't work.

AKA a blind bearing puller. I don't know where in the world you are, but if you are in the states, Autozone lends out tools for free. Some offer this item, some don't.

http://www.harborfreight.com/blind-hole ... 95987.html

Hi All

This thing has been giving me fits. Tried the red locktite...that stuff holds. It held so well that after I heated the case up to 250, and still couldn't pull the bearing out, I couldn't get the shaft out either. I eventually got pissed and just put the small propane torch right at the locktite as i spun the shaft then pulled to try to get the shaft out. My faith in red locktite is strong now. I eventually gave up and devised a puller that i could use to pull on the splines of the shaft without rounding/stripping the splines. After a couple of different iterations I finally got it perfect and hooked it up to the transmission. Figured that since the locktite held so well the first time that this time my homebrew shaft puller might take the bearing with it so I heated the transmission and tightened up the puller just past finger tight and waited for the heat to take affect. At the 5 minute mark into the heat with a hair dryer the locktite gave way and i was able to slowly pull out the shaft perfectly. AWESOME!!! The bearing was still in there so I started my search for a blind hole bearing puller. No store near me had one, many didn't even know what it was (including a guy working at a napa that owned a MkIII at one time). Finally found one an hour into the metropolis that I live on the edge of. Drove there, bought it, went home and hooked it up, heated, slide hammer a few times and it dropped out. AWESOME!!! Amazing how easy things are when you have the right tools! Everything looked good in the case. It appeared that someone put JB weld or sleeve retainer or lock tight or something on the bearing, which might be why the locktite on the shaft and pulling it didn't work. But after I cleaned everything up the old and new bearings were still a very tight fit. Froze the bearing, heated the case to about 275 and used the shaft to install. It got about half way in and stuck, it looked somewhat square to the case so I tapped the outer race sides with a wood dowel/hammer and after two or three taps in different locations it made a nice clunk/clink as if it was seated, so i tapped a few more times and heard another, smaller clink.

Now my question; how do i know if it is fully seated and square? The outer race protrudes a little bit (it easily catches on my finger nail on all sides.) But all sides seem to protrude equally. I put the inner race on the shaft and into the bearing and it doesn't look perfectly, vertically below the main shaft. I put the inner race in w/o the shaft and it doesn't look like there is a whole lot of room between it and the case. Is it possible to put it in almost the entire way and have it be slightly crooked? Or not in the last 10%?

I am assuming it is fine but i am a worrier about these things and don't want to mess up the case or the new bearing if i have to try to remove it and have another go at the whole thing...and certainly don't want my transmission to blow up 5 miles after i button it all up.

The drift will tell you when your home. A long drift to reach in, tap all around. The sound/feel is distinctive when a bearing is bottomed out in the pocket. The drift "bounces", versus a felt "travel".

Heat. (heat gun) . Cold. (freezer). Heavy leather gloves. Piece of cake.

Well, it all worked. It felt like the bearing was bottomed out so i figured I'd just put everything together and if it didn't fit then i would have to get back in there and drive the bearing in a little further. But, seeing as i had to shim around .050" to get the end play i felt comfortable with I figured the bearing was fully seated. Rode the bike 30 miles one day and about 20 the next and it worked/shifted beautifully! But a weird knocking/vibration has kept up and it was impossible for me to ignore so i started looking in the primary...but I think thats a different issue so that will be another thread.

Thanks everybody for your help!

I've read how easy these bearings come out of the trans case, but not mine, nor a friends. I ended up making a blind puller with some stuff I had around and it was still hard to get out with heat. I even had it in the gas BBQ cooker. It went back in good.

Both my crank bearings fell out in the BBQ cooker right on the grate, that was easy.

RGM motors has the layshaft roller bearing. I think you can also get it from a bearing supplier if you know the bearing #. So, here it is: NJ203EM, 40 x 17 x 12mm. Cheers, Dan.