Gearbox build - what am I doing wrong?

[alanscottj]

I have been battling with this gearbox and a rear wheel wobble ever since I first built the engine. When I put it all together it all 'appears' shimmed up properly, measured correctly and the gearbox moves correctly. Over time I get a slight wobble on my rear wheel which gets progressively worse. When I open up the gearbox to check it, the first gear is always loose.

This week the wheel has got lots of play yet again(see other thread!) and today I managed to get time to have a look inside. The first gear is now loose/has a bit of a wobble, not a great deal but it was solid. Today I have replaced the endplate bearing track and put a new bearing in, put it all together and there is no wobble on rear wheel (fingers crossed!).

So, I'm going to re shim and put it all back together. But obviously I want to get to the bottom of why , when it's all shimmed up correctly, over time it loosens up.......any thoughts?

Tia

P.s. I now have a new gearbox so the suspect isn't the box, new endplate, new bearing track, new bearing, inc new rear hub bearing, the only thing that is old is the layshaft which is an Original Italian one.

[bristolmod]

are you torquing up the rear hub before measuring tolerances etc?

[alanscottj]

are you torquing up the rear hub before measuring tolerances etc?

Yeah, left the wheel on when I last built engine up. Had the engine on a stand.

[wack 63]

You may have answered your own question by saying the first gear was solid, it shouldn't be. When newly built there's between 0.07 to 0.30 clearance if shimmed correctly so the first gear will have a bit of rock when trying to lift it. If you are building it up too tight then the shim and endplate are probably wearing as things are too tight so make sure the gears sit taller than the layshaft before fitting the large shim. I've not come across a rear hub yet that doesn't have a slight bit of play when rocking the rear tyre, probably due to how the needle rollers are spaced .

[alanscottj]

You may have answered your own question by saying the first gear was solid, it shouldn't be. When newly built there's between 0.07 to 0.30 clearance if shimmed correctly so the first gear will have a bit of rock when trying to lift it. If you are building it up too tight then the shim and endplate are probably wearing as things are too tight so make sure the gears sit taller than the layshaft before fitting the large shim. I've not come across a rear hub yet that doesn't have a slight bit of play when rocking the rear tyre, probably due to how the needle rollers are spaced .

Cheers Waxk 63 - ok, I bought a new layshaft today, fitted it and no more wheel wobble! It would appear the splines are slightly worn - I can feel a difference when I run my finger over each one.

Anyways, I thought that there isn't supposed to be any movement on the first gear? I shimmed the box up tonight and using a 2.5 shim means I can only just get a 0.10 feeler in there and the first gear is solid. But, if I use a 2.4 shim, the clearance is a good 0.10 and there is a very, very slight rock. So I am good to use the 2.4?

[wack 63]

Personally I'd go for the 2.4 shim and allow a little float. 0.10 would be good.

[alanscottj]

Personally I'd go for the 2.4 shim and allow a little float. 0.10 would be good.

Have fitted the 2.4 and this has left a definite 0.10 clearance, the tiniest of movement on the first gear, and I mean tiny, nothing that is going to interrupt kickstart engagement or anything. Happy days, hopefully this will be the end of the issue. But, I have managed to strip one of my end plate stud holes! It never ends! Luckily there is plenty of meat on there to do a helicoil to repair

[Scooterdude]

Personally I'd go for the 2.4 shim and allow a little float. 0.10 would be good.[/quoteI have managed to strip one of my end plate stud holes!:D

Yes just managed to do the same thing to mine, have ordered an M7 thread repair kit off of eBay for about £7. Just hope it works out as I don't really want to spend big bucks on time serts, anyone using the eBay kits?

[corrado]

It's a very stressed area, I'd bite the bullet and get a timesert fitted not something I'd personally use a helicoil on.

[drunkmunkey6969]

It's a very stressed area, I'd bite the bullet and get a timesert fitted not something I'd personally use a helicoil on.

+1


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