Drag on transmission mainshaft excessive?

April 74 had Portuguese bearing.

This is also a good visualization of how your tranny works.

[Removed broken link]

I don't think you want to has whining noises in your gears so replace all those gears that have lost their hardening. I replaced all mating pairs of gears [ in my own g/box ] where at least one of the pairs had gone through the hardening . That output gear [ that you show above ] works on 1st, 2nd, and 3rd gears so get rid of it. Get rid of what you call the second gear as well. No questions needed there.

Dereck

What's the proper tool for removing the bearing?

maylar said:

What's the proper tool for removing the bearing?

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If the case is heated sufficiently then the bearing should come out with the layshaft.
The bearing puller shown for removing the bearing from the layshaft isn't necessary as it can be levered off.

springs75 said:

Update for those interested: I washed everything and finished the inspection. The only thing I found that might explain the drag I was feeling was that the bushing on 3rd lay had a very light ridge on the kicker side where there is an oil groove on the layshaft. 3rd lay gear would drag when turning depending on where it was floating on the layshaft. I had to tap the bushing off the layshaft due to the small ridge. Runout on mainshaft was acceptable. Looks like 2nd gear has some fairly significant wear and should be replaced. The wear on 4th is much less and only on a couple of teeth and I will run with it. So besides gaskets and seals I will replace the following:

1. Both mainshaft ball bearings
2. Layshaft ball bearing with a roller bearing
3. 1st, 2nd and 3rd bushings just because I'm in there. The long ones in 4th are fine.
4. 2nd gear set


View attachment 184322nd gear. I will replace this set.


View attachment 18433
4th gear. This is the worst tooth. The photo makes it look a little worse than it is. I think this will be OK for a casual rider.


View attachment 18434
Is this the"exploading" Portuguese layshaft bearing?

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I would figure out why that gear is worn like that, i don't think i have ever seen one wear that bad on just one side like that. Something looks to be out of alinement, be sure the shafts run true.

Hortons Norton said:

I would figure out why that gear is worn like that, i don't think i have ever seen one wear that bad on just one side like that. Something looks to be out of alinement, be sure the shafts run true.

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The wear looks very similar to the photo below taken from the Old Britts site - gear on left. I will check everything. Trans made no noise and shifted smoothly.

Maybe it just the way the bushings wear, or it's normal?

Looks a lot more like porosity than wear from where I sit. Could just be the lighting on the photo, or aging eyes... A bit of slag inclusion during forging.

Thats what happens when gears wear. Thats life.

Update for those who are interested: I received the parts from Old Britts - they are all Andover Norton parts. The bushings are spot on as far as size. The new 2nd gear is a little on the small side on the ID so the new bushing wouldn't slide in, nor would the old bushing just as a test. I had to take about .001 off the bushing to get a sliding fit so no big deal.

I mentioned earlier about there being a ridge on the 3rd lay gear bushing which caused it to hang up and not slide off the shaft and could have been the drag I was feeling. Although I don't think this was a big issue, it looks like this was enough of a issue that Andover Norton modified the bushing to prevent it. See below:


Oil groove on layshaft



Slight deformation causes small ridge on ID edge of original bushing, which is straight cut



New bushing has relief machined on ID edge so ridge will not form

I'm curious. Did you measure and compare the widths of your new 2nd gears with the old ones?
When I replaced my 1st gear pair, the new 1st main was slightly wider that the original. Even though the difference was only 0.002", it caused problems..

NickZ said:

I'm curious. Did you measure and compare the widths of your new 2nd gears with the old ones?
When I replaced my 1st gear pair, the new 1st main was slightly wider that the original. Even though the difference was only 0.002", it caused problems..

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Thanks, I measured and the new 2nd gear is a smidge wider but as long as there is end float on 1st and 2nd gears on the mainshaft once it is tightened in the center plate bearing it is OK.

I've been sidetracked but back to finishing putting the trans back together. I'm checking the layshaft endplay with the roller bearing and my searching has yielded everything from "it doesn't really matter as long as there is some" to .005in on the Old Britts site. Mine is currently approx .020in endplay with .035in worth of shims, gasket installed and snugged but not torqued. Anyone care to state anything definitive regarding appropriate endplay range? Am I OK or add more shims?

I would keep in the 15 to 30 ran. to tight and you can cause issues and IMHO .005 is WAY to tight.

On the subject of worn gears, I replaced a few on my MkIIA and replaced the original layshaft bearing with the 'Superblend' upgrade.
Due to shimming the kickstart shaft I found my RGM kickstart wouldn't fit as the shaft was further in than previously.
This wouldn't be an issue if I'd kept the original kickstart lever...

I read the Mick Hemmings advice and replaced the superblend and shims with his 'correct' TB bearing which restored the layshaft positive location. The RGM kickstart then fitted with no clearance issues.
Incidentally, the gears I'd replaced had started to wear as per the ones I'd taken out...

IMHO the core issue - as evidenced in the wear pattern on the gears above, is that the mainshaft flexes, which in turn causes poor meshing of the gears, corresponding flex in the layshaft and broken layshaft bearing cages. The higher gearing of the later bikes seems to make this worse.

The high gear wear pattern clearly shows the displacement of the layshaft high gear.

The original layshaft bearing was not designed to be tolerant of the flex in the layshaft, whether from Portugal, India or the UK.
The TB bearing accommodates this by using a more flexible cage.

I don't know why OldBritts say pre-MkIII?
I've never had one so can't comment, but AFAIK it's the same bearing as earlier bikes?

htown16 said:

You may find that the new floating bushing are a bit tight and won't slip in freely. Mine were that way. Polish with some emery cloth until they are a sliding fit both on the shaft and into the gear.

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Never use emery cloth to polish transmission parts or a crankshaft journal. Emery can leave bits of abrasive in the polished part. Crocus cloth is the correct item to polish these parts.

https://www.mcmaster.com/sanding-abrasives/crocus-sanding-rolls/

B+Bogus said:

IMHO the core issue - as evidenced in the wear pattern on the gears above, is that the mainshaft flexes, which in turn causes poor meshing of the gears, corresponding flex in the layshaft and broken layshaft bearing cages. The higher gearing of the later bikes seems to make this worse.

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Well this was certainly a significant issue with these boxes when raced, and even more so when converted to 5 Speed.

The bush in the kickstart shaft doesn't help and allows too much movement in the layshaft as well. Manx 4 speeders with no kick start used a ball race and modified shaft and inner cover.

And of course there are two other things that can help, an outrigger bearing, and raise the primary ratio. This all works better in combination.

Most people who fit a belt drive end up with an increased primary ratio, but limited by the alternator mountings.

On my 4 speed box in the '70s I had the ball race mode done and fitted a 33 tooth crank gear and longer triplex chain! Very few people actually did this, though some used an Atlas clutch and adjusted the primary ratio that way.

It worked, which is just as well because the work to implement an outrigger required more enginnering skills than I had or had access to!

These days of course....just fit a TTi!

bill said:

I would keep in the 15 to 30 ran. to tight and you can cause issues and IMHO .005 is WAY to tight.

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Thanks. In that case I'll go with what I have.

SteveA said:

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The bush in the kickstart shaft doesn't help and allows too much movement in the layshaft as well. Manx 4 speeders with no kick start used a ball race and modified shaft and inner cover.
snipped

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Has anyone replaced that bush with a needle bearing? Is such a mode even possible? You would probably need to turn down the right side of the lay shaft to get a needle bearing to fit.
These issues suggest that investing in a premium synthetic gear oil would be a no brainer.

Charlie K