Gearbox hard shift after rebuild

Tony Pierce said:

I thought I read the layshaft shimmed in at .005" to .010"? I am about to do it myself, so advice is appreciated.

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Tony. I have my own thoughts on this subject based solely on mechanical realities, but my actual Commando experience is quite limited. Hoping some of the more knowledgeable folks will chime in.

Opinion: I went with the roller bearing but would install the proper ball bearing if I had it to do all over again. I believe the roller bearing inner race, which in my case is a light drive fit on the layshaft, requires shimming of the layshaft to maintain proper location of the inner race within the bearing itself. The ball bearing is less susceptible to end float since the inner race is more or less held in place; hence, more end float is acceptable with the ball bearing. (My own two cents/pence here, and this is not a recommendation.) I am open to correction as necessary.

I install all of my bearings by heating the case and often freezing the bearings. I never drive or press them into a cold aluminum case. It could ruin the interference fit.

Regards,

~998cc

998cc said:

Tony. I have my own thoughts on this subject based solely on mechanical realities, but my actual Commando experience is quite limited. Hoping some of the more knowledgeable folks will chime in.

Opinion: I went with the roller bearing but would install the proper ball bearing if I had it to do all over again. I believe the roller bearing inner race, which in my case is a light drive fit on the layshaft, requires shimming of the layshaft to maintain proper location of the inner race within the bearing itself. The ball bearing is less susceptible to end float since the inner race is more or less held in place; hence, more end float is acceptable with the ball bearing. (My own two cents/pence here, and this is not a recommendation.) I am open to correction as necessary.

I install all of my bearings by heating the case and often freezing the bearings. I never drive or press them into a cold aluminum case. It could ruin the interference fit.

Regards,

~998cc

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This is very good thread from the best
https://www.accessnorton.com/NortonCommando/shimming-the-kicker-shaft.20856/

998cc said:

Thanks Ashley.
I'll try again with the new pinions. Ordered new shift forks and fork shaft since all are worn. With the original pinions, it does work, but without shims, the gap is wide at .103". It does shift well at .020" shimmed, so I will shim to .020+ with the new pinions and then test. Don't know if it is possible, but with the next build, I'll try to determine if the shift forks are binding prior to starting or taking the bike on the road. In the meantime, good riding weather here.

Thanks again.
Regards,
~998cc

View attachment 9989

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No problem, I would aim for the top end, you do not want to shim tight otherwise the tolerances across the various parts in the line could be compromised.

Following up on this old-ish thread. To recap, in 2018 the gearbox in my new-to-me Commando shifted very well but was whining in first and second gears. These sets were visibly worn and were replaced along with a new sleeve gear using new AN spares. Hard, crunchy shifting followed. Re-installing the old pinions brought back smooth shifting.

Last week, I took the pinions out of the gearbox, measured and examined them for odd wear patterns and such. Third gear main appears to be of lesser quality than third gear lay. Third gear lay is signed "AH" whereas third gear main is not signed at all. The dogs on third gear main are worn where they mesh with second gear main. Given this, a new set of third gear pinions from Old Britts have gone in. Also changed over to ATF per a recommendation in another thread. Lay shaft end float is shimmed to .030".

Just returned from about 75 miles of riding through the Sierra Nevada gold country; shifting is very much improved!

Curiously, the new third gear set whines a bit--any thoughts on that?

Regards,
~998cc

998cc said:

Curiously, the new third gear set whines a bit--any thoughts on that?

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I don't have any ideas of why the 3rd gears are whining on your gearbox, but interestingly, I have just fitted some new A. N. gearbox parts including new 3rd gear on the main shaft and 3rd gear on the lay shaft and they are whining a bit already with less than 80 miles on them! I wonder if anybody else has had this problem except us?

Thanks for your follow-up.

When I do a g/b overhaul I check the main and layshaft for run-out as part of the initial inspection before deciding what parts I'll need. The shafts don't tolerate slam-shifts well which the one-up, three-down seem to invite...

Did you check the shafts for run-out?

Best.

I am having a similar experience. Went in to change the lay shaft bearing. Noticed a little wear on 1st main so replaced the pair. Put it back together and wouldn't shift. After 2 weeks of trying this, that and the other thing, it came down to the tolerances of the new 1st main vs the old main shaft. In looking at gears and shafts from different boxes I have, I noticed a lot of variation. If you get the wrong combination, you have trouble.

RoadScholar said:

Thanks for your follow-up.

When I do a g/b overhaul I check the main and layshaft for run-out as part of the initial inspection before deciding what parts I'll need. The shafts don't tolerate slam-shifts well which the one-up, three-down seem to invite...

Did you check the shafts for run-out?

Best.

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I did visually check for run-out while the shafts still supported by the bearings in the chain side of the gearbox case but did not set them up in a jig.

In any case, all is well now. Yesterday, I went out for a 90 mile ride on the local back roads and secondary highways. The bike is running great with the Amal Premiers and Tri-Spark ignition, (yes, I know). A new set of Ikon shocks made the ride that much more enjoyable!

Regards,
~998cc

I think ATF is too thin for a gearbox. (I think Comstock uses ATF in the gearbox but he rides a lot of highway miles) Fine for the primary.

Try something thicker in the gearbox and see if the whine goes away.