layshaft bearing upgrade

Going to do the layshaft bearing upgrade next week on my '73 850, and I'm leaving the gearbox on the frame during the procedure. I've got lots of great info from this forum so not anticipating any problems. I'll be installing a FAG 6203.P63 bearing, and changing out the kickstart layshaft bush also. One question for those that have done the upgrade with the gearbox on the frame....which works best, having the bike sitting up on the centerstand, or propped up on the kickstand?

I thought the roller layshaft bearing upgade was a FAG 203 C3 ? As far as centerstand vs side, I would say centerstand. Then again ... I would pull the primary, then the motor, and do the gearbox on the bench. To me, it's worth the added hassle. Working on it on the bench, having a vice handy, putting the whole gearbox shell in the oven to install the new bearing. It's just so much easier. But however you do it, good luck !!!

nortriubuell said:

I thought the roller layshaft bearing upgade was a FAG 203 C3 ?

Click to expand...

The layshaft roller bearing upgrade is the FAG NJ203 (C3), hopefully the 6203.P63 bearing that singring is referring to is the FAG 6203TB (P63) phenolic cage 'Mick Hemmings' ball bearing?

I've just done my gearbox (850 MkIIA) and was hoping to do it in the bike, but there was no way I was going to get the bearings out without damaging something. I took the gearbox shell out with the bike on the sidestand by removing the rear isolastic bolt and the top and centre bolts holding the cradle to the crankcase. The cradle was then dropped down with the swingarm still attached, pivotting on the slackened bottom cradle bolt until there was enough space for the shell to clear the back of the crankcase. The oil filter had to come off, I took the exhausts off to improve access and there's no centrestand fitted to my bike, but everything else stayed in place. I wrapped a length of rope around the engine & frame downtubes to stop the motor falling back - not sure if this is necessary, but better safe.... Above all, use common sense and watch out for the rocker oil line if it goes inside the cradle! Refitting was easier than I expected, but clearance is pretty tight with a complete 'box instead of an empty shell.

I fitted the Mick Hemmings recommended layshaft bearing, which seems to be a ball bearing with a very substantial non-metallic cage. Incidentally, the bearings were really tight in my shell, but just fell out in the oven at 250 degrees F. New ones dropped in at the same temperature - no need for force at all. No way could I have done this with the shell in the bike.

Hope this helps

Mitch

Yes, the bearing I'll be using is the Mick Hemmings recommended FAG 6203TB.P63
Thanks for the replies.

mitchp said:

No way could I have done this with the shell in the bike.

Click to expand...

Well...I found it was easy to change the layshaft bearing with the gearbox shell in position, no problem at all.

There are many ways to skin a cat they say. I did mine with the bike on a lift, on the center stand and did not pull the trans. I used a small torch to carefully heat up the area and a Small internaly fingered puller. If that is about all that is being replaced it seems crazy to go through all the work to pull the trans. That said, I'm no expert & I have heard that it's not good to heat aluminum directly with a torch so I hope I didn't damage anything due to my own ignorance. I was very careful & used a laser thermomiter to keep an eye on the heat. All done in a afternoon at a friends restoration shop which was nice. Everything else inside seemed ok, I did replace a few springs and the kick start pawl just for good measure. For me it was a good experiance because I had never gone so far as to pull gears out of a trans & was a bit afraid them. Now, while I know I'm no pro I'm not afraid to work on them.

I am 1/2 way through this procedure on my 850. Bike is on the centerstand and the gearbox in-place.
Bearings were removed easily with an electric heatgun.
Once the weather gets a few deg warmer I'll finish it off.

I did this not too long ago. Center stand, on a lift, gearbox in the bike. It went very smoothly - no problems. I did a write up on my exploits here http://www.doov.com/apps/nortoncomp...aft-bearing-upgrade&catid=1:upgrades&Itemid=8.

Good luck!

L.A.B. said:

mitchp said:

No way could I have done this with the shell in the bike.

Click to expand...

Well...I found it was easy to change the layshaft bearing with the gearbox shell in position, no problem at all.

Click to expand...

Fair enough. I tried, but couldn't get the case hot enough in the bike to release the layshaft bearing and I don't have a blind bearing-puller/slide hammer. Even if I'd got the old one out, my concern would have then have been the new bearing going in part way and stopping. Therefore I took the safe option and pulled the case, which was actually easier than I expected.

I did 2 gearboxes last summer out of the cradle, heated in a small gas grill. In both cases the layshaft bearing would not drop out with heat, I had to fabricate a puller and they finally popped out. Installation was much easier. It seems to be the luck of the draw if you can get them to come out easily. BTW my mainshaft bearing came out with the mainshaft, no heat, so I put some sleeve retainer on it with installation. Hope it stays put.

I guess it's worth trying to get it out in the bike, if not, more work is required.

Dave
69S

mitchp said:

L.A.B. said:

mitchp said:

No way could I have done this with the shell in the bike.

Click to expand...

Well...I found it was easy to change the layshaft bearing with the gearbox shell in position, no problem at all.

Click to expand...

Fair enough. I tried, but couldn't get the case hot enough in the bike to release the layshaft bearing and I don't have a blind bearing-puller/slide hammer.

Click to expand...

I did remove the primary drive-so that I could heat the case on the outside in the area directly behind the layshaft bearing, and it didn't take very long to get it hot enough.
The original layshaft bearing is often a reasonably tight fit on the layshaft-as mine was, so it was just a matter of heating the box and gently pulling on the layshaft until it came out-with the bearing still attached, and with the new bearing fitted to the layshaft I used that as the bearing fitting tool as Mick Hemmings demonstrates in his gearbox rebuild video, even though he has the gearbox shell out of the bike, he set the gearbox shell upright before installing both D/S bearings (Mick fits both D/S bearings to their respective sleeve gear and/or shaft and installs them both all in less than 20 seconds).

I don't know if you have a bike bench or lift, but it certainly does make this sort of job much easier having the gearbox at a convenient working height.

Mine came out on the shaft when I heated the case from the back as well. It was simple. Now the main bearing that was another story!

Russ

I guess this is just luck of the draw, because my layshaft was loose in the old bearing. Old sleeve gear bearing fell out at 200 degrees F, but the layshaft bearing was still rock solid at 240. My oven only goes up to 275, so I was getting a bit anxious but when the thermometer hit 250 there was a thud as the bearing hit the bottom of the oven. For refit I heated the case straight to 250 and the bearings just dropped in exactly as per the Hemmings video.

Hope I won't have to do this again, 'cos I ended up with new bearings and bushes throughout plus new second gear pinions and kickstart shaft. My wallet has yet to recover.......

(If I was doing it again I'd pull the trans straight away)

I have issues! A double whammy..
My layshaft bearing refuses to go back in all the way home.I've had the heat gun on it for like 10 mins and its very hot.The bearing just sits in place less than 1/2 of the way in.Maybe its not hot enough?
now if that wasn't bad enough I sprayed the bearing with contact cleaner and the bearing doesn't feel as solid as it did previously.Do you think its ruined?