2nd Layshaft Bearing Failure! Please Advise

When I first got this bike back on the road after it sat abandoned for decades in a southern California shed, I wasn't too concerned with the layshaft bearing issue. The reason for my lack of attention to a potential disaster was that the sprocket cover thats forged into the primary case is all busted up.



I concluded that at one point, the PO had a layshaft bearing failure, locking the rear wheel, and breaking the chain and sprocket cover.


Well I've been enjoying this bike for years now, but more than a few months ago, after a great ride home the previous evening, the kickstarter locked up as I was preparing for my morning ride into town. So the bike sat up at the house for weeks until I found the time to haul it to my shop, 25 miles down the mountain.




there it sat collecting dust for months on end, and then I finally got into it, as our normally windy and wet weather has been sublime for the past 6 weeks. this is what I found;



lay and mainsheet gears, bushings and kickstarter pawl show almost no signs of wear.



and as I suspected, the layshaft bearing is a japanese replacement that has a very slight clicking to it when turned…. this must be why the kickstarter locked up as it did, I hope.

while I'm in there, and I seem to have a low cost solution to my problem, I guess I'll do the mainshaft bearings as they seem original (LS7 V3 in the cover)

could someone please recommend the best replacements or direct me to most applicable of many threads on this issue?

MANY THANKS!!!!

Don

The Bonneville , Japanese parts feel off , useually within a week .
Must be difficult for it to reject the forign components , when theyre internal .

If your punishing , German ones are good , but switish better maybe , and yankee ones o.k. .

But Jap ones were made from recyled Zeros , and polish ones from recyled T 34s , so wernt the correct grade material .

If one costs 1/4 of a good german or switzerland one , it may be a bit cheap & nasty .
Ceramic ones are LESS Shock resistant .

Andover has the best available. I would suggest the roller layshaft which is what they carry along with the open sleeve gear bearing. Some people sell a sealed bearing replacement for the sleeve gear but they don't have as high a load capacity as the original. Jim

DonOR said:

and as I suspected, the layshaft bearing is a japanese replacement that has a very slight clicking to it when turned…. this must be why the kickstarter locked up as it did, I hope.

Click to expand...

Unless the bearing was sufficiently worn enough to cause some shaft misalignment, then I don't quite see how slight clicking of the bearing could have caused the kickstarter to completely lock up - as (the free running) layshaft 1st gear is the only layshaft component that must turn during the kickstarting process, the layshaft itself is, basically, "idle".

Roller or superblend is the go
Norvil box kit is worth thinking about which is cheaper than individual parts
As long as your box isn't cracked too badly (a lot have hailine crack between lay and main) then it should be OK
It pays to keep in mind though the box shell was designed for a 500 cc motor

Jed

Matt Spencer said:

The Bonneville , Japanese parts feel off , useually within a week .
Must be difficult for it to reject the forign components , when theyre internal .

If your punishing , German ones are good , but switish better maybe , and yankee ones o.k. .

But Jap ones were made from recyled Zeros , and polish ones from recyled T 34s , so wernt the correct grade material .

If one costs 1/4 of a good german or switzerland one , it may be a bit cheap & nasty .
Ceramic ones are LESS Shock resistant .

Click to expand...

thanks Matt good advise on the source... it does seem like many of those Asian bearings don't last long.

comnoz said:

Andover has the best available. I would suggest the roller layshaft which is what they carry along with the open sleeve gear bearing. Some people sell a sealed bearing replacement for the sleeve gear but they don't have as high a load capacity as the original. Jim

Click to expand...

Thanks Jim, I'll check those out soon, anxious to get back on the road.

L.A.B. said:

DonOR said:

and as I suspected, the layshaft bearing is a japanese replacement that has a very slight clicking to it when turned…. this must be why the kickstarter locked up as it did, I hope.

Click to expand...

Unless the bearing was sufficiently worn enough to cause some shaft misalignment, then I don't quite see how slight clicking of the bearing could have caused the kickstarter to completely lock up - as (the free running) layshaft 1st gear is the only layshaft component that must turn during the kickstarting process, the layshaft itself is, basically, "idle".

Click to expand...

Les this is what concerns me as well, that clicking is very, very slight. The pawl, bushings, shafts and gears almost look like new, and the main shaft, still in place, is solid... I guess I'll mic those bushings and see what's up. Could it be that the pawl simply "jammed", a rare anomaly?

Jed said:

Roller or superblend is the go
Norvil box kit is worth thinking about which is cheaper than individual parts
As long as your box isn't cracked too badly (a lot have hailine crack between lay and main) then it should be OK
It pays to keep in mind though the box shell was designed for a 500 cc motor

Jed

Click to expand...

Thanks Jed, I'll take that advise and pull the primary drive and mainshaft so I can have a better look at the case, and give it all a good cleaning as well! cheers, Don

L.A.B. said:

DonOR said:

and as I suspected, the layshaft bearing is a japanese replacement that has a very slight clicking to it when turned…. this must be why the kickstarter locked up as it did, I hope.

Click to expand...

Unless the bearing was sufficiently worn enough to cause some shaft misalignment, then I don't quite see how slight clicking of the bearing could have caused the kickstarter to completely lock up - as (the free running) layshaft 1st gear is the only layshaft component that must turn during the kickstarting process, the layshaft itself is, basically, "idle".

Click to expand...

+1... you HAVEN'T found the smoking gun. Keep looking. "I concluded that at one point, the PO had a layshaft bearing failure, locking the rear wheel, and breaking the chain and sprocket cover." That was a flawed assumption, chains pile up for other reasons.

RGM is another option

http://www.rgmnorton.co.uk/buy/gearbox- ... k3_557.htm

I'd take a close look at the kickstart pawl and spring. It sounds like maybe the pawl wasn't retracting.

That bearing looks OK to me, when they fail you won't be going no where as the bearing explodes, you will find all the balls at the bottom of your gearbox, I was lucky with mine it blew just as I was leaving home, didn't even get out of first gear, lucky for me, I say you have a pawl problem as they will lock the kick start some times.

As for the broken Primary, I say at some time it broke a chain and it flew off the bike as mine did that many years ago when young and silly, dropping burn outs my chain broke and spat out the back of the bike for about 100 yards, when I retreived it the chain it was missing about 10 links and my case broke like yours.

Ashley

Hm, does not compute. We all hate our own mysteries but love everyones else's. Mild click is just in hand annoyance issue at this point but on the way out and will never be easier. Kicker ratchets commonly don't ratchet to swing free and rarely if ever cause a stuck KS lever. Bad cog dogs mess with shifting not KS function. Should be some galling or metal chip or piece broken evidence, hm. What would Sherlock think? If KS got stuck on the down stroke it might simply have hung up on the foot stalk so put magnifier where they might collide.

The jammed kickstart issue is a bit mysterious - the bushes are known to work their way out, and the pawls can fail, but to lock the box solid would be more symptomatic of it dropping between 2 gears or something similar (unlikely?) - I'm thinking that to get what you're describing either the mainshaft isn't free to turn, or the kickstart shaft has some issue, but what I don't know!
So that's helpful... :roll:

With regard to the layshaft bearing, I personally wouldn't go the superblend route again.
Although the bearing is definitely man enough, it doesn't positively locate the layshaft, and I found that shimming the kickstart shaft to control the endfloat creates other issues: I shimmed the kickstart shaft using Iso shims (I think this is the 'traditional' method?), and it pushes the kickstart shaft further into the gearbox. In my case it means the kickstart is no longer adequately clamped on the shaft, so I'll be replacing the bearing with one of these this winter:

Available from Mick Hemmings



I don't think the issue is with the quality of the original bearing - it was underspecified for the job, although I'm sure it was fine in the Model 50 and G3...
The cages break up due to shaft flex, and the fibre cage bearing accommodates this yet still provides positive location for the layshaft

I would be a bit careful with shimming and getting the kickstart further in
The superblend bearing allows for a bit of movement to absorb some shock
The box stands up well considering the power feed



Jed

Like several others above, I also don't think you've located the cause of the lockup. As you say, all the parts seem to be in good condition, including the pawl and the ratchet teeth in 1st gear. It's still a mystery, which is a worry.
B+Bogus makes a good point about the shimming of the kickstart reducing the amount of splined shaft protruding from the box.
However, on the plus side, it results in the pawl engaging more deeply in the gear which has to be a good thing.
In my case I was able to shim the shaft to about .005" end play and still get the kickstart fully onto the spline.

Cheers
Martin

Ron L said:

I'd take a close look at the kickstart pawl and spring. It sounds like maybe the pawl wasn't retracting.

Click to expand...

Ron, if the pawl wasn't retracting, then the lever would just move freely, up or down, wouldn't it?

I correct myself; if the pawl was stuck in a retracted position, then the shaft would fall down, and not engage when brought up....

if stuck extended, one could get a kick, then the lever wouldn't ratchet back up

B+Bogus said:

The jammed kickstart issue is a bit mysterious

- I'm thinking that to get what you're describing either the mainshaft isn't free to turn,

Click to expand...

Something jammed in the primary chain/sprockets perhaps?

If dis-engaging the clutch allows the kickstart to turn the mainshft, wouldn't that point to a primary case malfunction?

hows the bushes?