Stuck on Layshaft Bearing upgrade

I've got a '75 MkIII with about 4700 original miles on it. I'm assuming the layshaft bearing is in need of replacement as I'm pretty sure the gearbox has never been cracked. I JUST had the primary apart, so I wasn't looking forward to tearing it down again to remove the trans from the bike. As a result I'm attempting to do this in situ. I understand it's possible, but sort of a pain. Anyway I got to a point where I was sort of thinking the layshaft would just slide out. Of course it dosen't. This makes it a lot more complex to remove the bearing in the back. I assume I'm supposed to get the layshaft out of there first - it looked like it fell out in the Hemmings Video... Now I'm wondering if that only happens if you're already running the replacement roller bearings. If you happen to have the original ball bearing type, then could the layshaft be pressed into the race? How do you get this apart?

Help Mr. Wizard....



--David

No, the shaft is not a press fit in the bearing. You should be able to pull that off the layshaft. Getting the layshaft bearing out for the 2 transmissions I did involved a puller and heat. You can make a puller with a couple of small hex bolts, but you need to grind off the heads so they will go between the ID and the bottom of the gearbox. The layshaft bearing has space behind it go get a puller in there, I had to do that with both trans I did, and plenty of heat. They did not fall out like Mick's, unfortunately, but with pulling and heat. Your mileage may vary. Good Luck, I feel your pain.

Dave
69S

DogT, Thanks. OK so that layshaft if supposed to come out. Good. I've tried pulling by hand to no avail . Is there some trick?

Thanks on the puller idea - I have a pilot bearing slide hammer that should work well if I can get enough heat on it. How did you do this? I'm thinking I'll try using a propane torch.

-- D

I had one race stuck even with box out and frying hot, but instead of a puller bother I took it to welder who tacked a rod on the race, waited 30 sec for the heat to move to the shell then with pliers just pulled the thing out by hand.

I've had the lay shaft be a rather tight press on the ball bearing race and roller races.
Took some heating and/or careful hammer drifting to get them on and off at hand on desk top with vise to hold shaft in thick leather. Don't forget to check shafts run out/trueness.

Heat is part of this repair so be sure to have extinguisher at hand.

napanorton said:

DogT, Thanks. OK so that layshaft if supposed to come out. Good. I've tried pulling by hand to no avail . Is there some trick?

Thanks on the puller idea - I have a pilot bearing slide hammer that should work well if I can get enough heat on it. How did you do this? I'm thinking I'll try using a propane torch.

-- D

Click to expand...

You are lucky if the shaft is a tight fit in the bearing. Heat the case-preferably with a hot air gun but a torch will work if you are careful and spread the heat around. Don't hit any gears directly with the flame. When the case gets hot enough then you can pull the shaft out by hand with the bearing stuck on the end. Then removing the bearing from the shaft is easy. Jim

Well, my layshaft just pulled out, but I had the gearbox out. It may be tighter in the machine with the mainshaft in situ. Those 2 gears you have in your picture should come out and that may help, there's no trick. Since I had the gearboxes out, I just put them in a small gas grill and heated them to about 350, but then also used a home made puller and then also applied a LP torch to the layshaft bearing on the outside. They finally popped out, they never just fell out like Mick's, sorry to say. The mainshaft bearing just came out when I took out the mainshaft, but yours is still attached on the drive side, so you can't do that. Others may have done it with the GB in position, I never tried that. Hopefully someone will speak to that.

Dave
69S

Out of the four layshaft bearings I have replaced this year in the bike, one had a bearing that fit the shaft tight enough to heat the case and pull the layshaft and bearing out by hand. I had to use a pilot bearing puller on the rest of them. The mainshaft and gear should cause no problem.

If it were my bike, I would say "in for a penny, in for a pound". It's not hard, just a little time consuming ... oh the joys of owning a Norton, and honing your mechanic skills the longer you own it. Here is my two cents ...

I would pull dismantle the primary, remove the gearbox case, place it in an oven, (250-300 degrees for 20 minutes) and then knock the case on a block of wood. Aluminum alloy of the case expands MUCH more than the steel of the bearing. Bearing should drop out, trust me, they have ALWAYS come out for me. For added insurance, you can spray some PB blaster penetrating oil around the joint where the bearing and the case meet, before you put it in the oven. (Electric oven only please !) I woud also do it right, and replace all the bearings from a rebuild kit. I know, I know ... it is a pain but this is the right way to do it IMO. Then, you probably won't have to touch the gearbox again in your lifetime. I know people use heat guns and torches, but nothing gives even heat all around like putting it in an oven. With a heat gun or a torch, you just don't get even heat disipation, period. Plus, you do not risk destroying the heat temper of any of the gears; if you use an oven. If it is still really stubborn, and this does not work; you might have to bite the bullet ... and follow Hobot's advise. His would be the next drastic step. Keep us posted, cheers !

Thanks for the all the help so far. I hope to get back to it after dinner.

So the fact the bearing is stuck on the end is good - as it hopefully will come out together. Should I abe able to get the rest of the gears out of the way first? I was hoping the ones on the layshaft would slide off, but they don't seem to want to - at least not at first try.

Yes a good sign if shaft is sorta stuck in the bearing, then likely can just heat the steaming snot out of the shell and pluck the whole assembly right out by hand.
Test pull as heating but it can take almost frying pan hot and heat leaks on top of that being attached to cradle. Focused heat melts powder coating and bubbles paint I found. After trying it both ways I now perfer the more disciplined meditative state of undoing what ever it takes to get parts in hand to deal with/examine in perfect comfort - especially if I'm newly familiar with what I just put back on it good state, than fart around knuckle busting strained reaching in peering around.

To me this is intimate handling of art deco watch works not under hood boredom of utilitarian car or truck. About every time I've taken a seeming short cut later I regretted it more or less. Seems to be about a wash either way time wise.

Mr. Hudson also took sand paper to TS crankshaft to get ball bearing to slide on off by hand at room temp, taking no care to get a round surface just sloppy good fit.

No need to pull primary or gearbox,propane torch to the shell area of bearing,outer or inner,no flame on any gears or shafts, grab layshaft with leather glove and pull out. Easy. Clean of grease ,oils to prevent fire, extinguisher on hand. Pop off old ball bearing with screwdriver , toast bearing with heat if tough. Press pre-frozen new roller bearing outer shell into still hot gearbox. tap new inner race onto layshaft. oil up bearing and reassemble. Good to go.

comnoz said:

napanorton said:

DogT, Thanks. OK so that layshaft if supposed to come out. Good. I've tried pulling by hand to no avail . Is there some trick?

Thanks on the puller idea - I have a pilot bearing slide hammer that should work well if I can get enough heat on it. How did you do this? I'm thinking I'll try using a propane torch.

-- D

Click to expand...

You are lucky if the shaft is a tight fit in the bearing. Heat the case-preferably with a hot air gun but a torch will work if you are careful and spread the heat around. Don't hit any gears directly with the flame. When the case gets hot enough then you can pull the shaft out by hand with the bearing stuck on the end. Then removing the bearing from the shaft is easy. Jim

Click to expand...

Yep thats what I did.

Napa, the good finding of snug fit that heat released nicely in situ also means more trouble to get a new race back in. I've had bearing/race go in slightly cockeyed and then thermal expand and lock in so took extra hot to work back out and get another run at it- after bearing refroze smaller again. Of course I ain't a mechanic so yours may go in slick as can be first shot a bullseye.

I've done 4 AMC boxes, 2 fit as advertised, one was too loose a bore to re-use- fell right back out when cooled off to a chill and another was unexpectedly tight.

Now that I'm almost over my turkey stupor, I want to get back to the trans. How the hell do you heat the tranny case to get the layshaft bearing out with the gears in place? (I've figured out that 3 and 4 lay gear are trapped) I'm under the impression a hand held electric heat gun won't deliver enough heat, and with a propane torch you can't hit the gear teeth. With so little room, what is the procedure/equipment? Do you heat the outside? Inside? Induction heating? I'm trying to hit 350, right? The bearing is the freezer - so hopefully that will just slide in, once I get the old one out.

Any help appreciated.

-- David (still stuck)

A handheld heat gun will definitely create enough heat to do it. I use an 1100 watt gun to do them regularly. Just prop it up so it is blowing into the case but not directly on the shaft and let it run until a wet finger begins to sizzle when you touch the top of the case. Then the bearing will come right out. Jim

Heat gun or even good bathroom hair dryer will do the job safer and faster than a tiny propane torch and way less fire hazard as oil vapors rise. My home hair dryer has rather more heat out put than my mechanics heat gun. Heat gun will get higher local temps but not as much area of total heat output. I torch fasteners and small cogs on shafts but hair dryer cases and big suff like fork caps in yokes and gear box.

Again I mention getting a bearing race out with normal good tight fit is one thing getting it back in in normal good tight fit can give ya fits if not brave enough to heat to lower frying pan temps 300-400 F. If it don't seat full first go then it can get trapped in skewed and then absorb case heat and swell in place good and tight half installed crooked. Then you learn how really hot it takes to remove to try again : (

It race does get trapped crooked it may then require gear box shell out on bench to deal with. Best wishes on labor saving bowed down worshiping posture devotions to your Commando.

If the layshaft is used as the fitting tool, then the (roller or ball) bearing should drop in easily?

lab, ONLY IF FIRST TRY IS PRETTY DARN DEAD ON, ESPECIALLY IF INTERFERENCE FIT CLOSE TO NORMAL. The more correct the final fit the more important to heat enough and aim well enough, another reason on good shape/condition stuff I prefer to have it out on desk top, now I know better the hard way. But I'm not a good mechanic as many here so have to fudge everywhere I can or face redoing often damaged stuff on first learning curve. I get pensive groin/jaw tension to re-heat as high as it takes to get a cockeyed trapped race out, thinking I'm removing the temper of hardened surfaces going over 500' F to have half a change to remove again in home shed. Most may only need heat to water sizzle I now heat to oil smoke for first time does it once.

While on subject I've yet to hear a single success story of any type loctite holding a bush or bearing stable, nuts and fasterners yes, me too, but not in tranny or engines, ever. Jim Comstock verified my idea to use |JBWeld in loose bores.
Hi heat OVER 500' F will soften it to cold honey state. Al don't loose its intergrity till close to 1000 F and nil distortion if whole case heated instead of just spots.

My favorite heater is tank top propane pancake burner on high with wire and heavy leather gloves to handle. To get a fused brake caliper cap off I had to heat to oil smoke and put dry ice on the cap and almost broke vise mounts off even then. Nothing lesser did anything but tend to wallow out the cap holes or bugger over the hardened tool pins. UGH>

To all who chimed in - thanks! A 1200 watt heat gun worked the magic. Got the case up to around 200 (as my infrared thermometer measured) and the old Portuguese ball bearing unit came out easily. My frozen new roller went in clean, square (thanks for the heads up on the potential for crooked diasater hobot!) and made a nice solid seating sound.I should now be able to reassemble and get on with my life. I hope to post some pics tomorrow, just to complete this thread. Thanks again to all, this site is the best.

-- David

Ah pooh Dave, you missed out on deeper joys/lesions Norton testing. But glad of it and hope I luck out short cut way next time too. Go wear it again a long time from now.