speedo drive gearbox jamming

[John Carney]

Hi,
I had an excessive rear wheel wobble that I couldn't get rid off even with the adjuster sleeve tightened as far as it would go. QD wheel. Taking it to a local garage the advise was to replace the bearings which seemed reasonable. The bike's done about 50k and could be on the original bearings as far as I know.
With the new ones in the wobble has disappeared but if the speedo gearbox is fitted it jams as soon as the wheel spindle is tightened up. ( Its a fairly new speedo gearbox and all was OK before )
The replacement bearings are from AMC classic spares part 014868 and I'm pretty sure I've got everything together right.
The left hand nut on the rear wheel spindle seems to have tightened a couple of turns more than before when i do it up so I think maybe the new bearings could be narrower ?? I think maybe the speedo drive boss is slightly more pulled in, which isn't leaving any 'slack' for the speedo gearbox drive so it's jamming on the bearing adjuster ?
I wondered if anyone had ever come across anything similar or has any advise to what could be causing this problem.
I've removed the speedo gearbox for now so that at least I can still use the bike.
Thanks,
John

[dave16mct]

This happened to me when I changed the speedo gearbox. I made a 2mm thick shim to fit inside the speedo gearbox. It's been OK since. Are you sure you've assembled the parts on the speedo side correctly? The oilseal goes outside the cup on the speedo side.
Dave

[Duncan]

I have had one speedo gearbox a few years ago that would foul when tightened up, the felt seal retaining ring appeared to be protruding too far compared to other speedos so I removed from the ring from the speedo body and reduced its depth on some wet and dry this cured the problem.

[John Carney]

OK, many thanks guys.
I will take everything apart again just to double check and if all is as it should be I think I will shim it as Dave Suggests. Either way I'll let you know the outcome in a few days when I've had a chance to look at it again.

[SPRIDDLER]

I think this photo from the Archive of the whole assembly by the late 'Biscuit' is relevant........

Hub Rear cutaway.JPG

[John Carney]

Hi, I tried a shim 1mm (instead of 2mm as suggested ) inside the gearbox which I had, that did provide the clearance needed ( I thought ) but after a few miles the speedo gearbox still 'grabbed' and that was the end of that !
Thanks spriddler. I have seen this rear hub cutaway before. When I spoke to Steven at AMC classic spares he made several suggestions one of which was that maybe the adjusting ring was not the correct one and looking again at the photo you attached I think this may be the case. So I've ordered a few replacement parts and will try again once they arrive. Cheers, John

[griffin]

I have had one speedo gearbox a few years ago that would foul when tightened up, the felt seal retaining ring appeared to be protruding too far compared to other speedos so I removed from the ring from the speedo body and reduced its depth on some wet and dry this cured the problem.

Just had a similar problem with a new L.F.Harris made speedo. Found out that the felt seal retaining ring could be pressed in a little further and thus clearing the lock ring but this then made the speedo notchy and difficult to turn . What was happening was the seal retaining ring was pushing up on a large dia washer which in turn was touching the speedo gear . So ground a small flat on the edge of the washer giving clearance of the gear. The seal retaining ring was then pressed in fully home up against the washer which was itself up against a lip , I then had clearance of the lock ring and a free turning speedo gearbox..

[56G80S]

Just as an aside, I replaced the original speedo gearbox last year with one from Feked which was bored to the correct spindle size, at the time AMC Classics and Jampot Spares didn't have such stock.

There was a small hiccup with the first supplied, which felt notchy when turned by hand. Feked were very patient, helpful and replaced with another which has now down a couple of thousand miles with no difficulties to date.

The wheels are both on the original taper bearings, which have always been kept greased and not overtightened - death to taper bearings.

Johnny B

[griffin]

The wheels are both on the original taper bearings, which have always been kept greased and not overtightened - death to taper bearings.

Johnny B

As a matter of interest how much play did you give the taper bearings ?
I'd read that you tighten up the adjusting ring then back it off by half a turn which seems excessive to me.

[56G80S]

From memory the instruction was to achieve barely perceptible rim rock. Whatever that equated to in tightening and backing off, I don't recall for the Matchless but the rim rock approach is how I've done other taper roller bearings, such as sidecar wheel.

Johnny B