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500T Gear and Clutch issues

Submitted by garry_tyler on Tue, 04/07/2023
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Hello,

I'm looking for some advice re my newly acquired 500T.

I am having issues with the bike dropping out of 3rd gear when motoring along, all the other gears are absolutely fine. I've cleaned and reassembled the mechanism in the dolls head, the pawl doesn't look new but in reasonable shape. I've replaced the bushes in the head with new ones from racing Vincent and replaced the pins with slightly over size to reduce slop. I'm still having the same issue of jumping out of 3rd. I have noticed sometimes after it jumps out a very slight touch down on the shifter puts is back in again...

I read that there shouldn't be much end float on the output shaft. When the clutch is attached it seems quite good with hardly if any float. However, when the clutch is off there is about 1.3 mm of end float.. Perhaps a someone could advise me on what is 'normal'. I don't have a manual or guide.

This brings me onto the clutch. When on the shaft there is some rocking movement, when gripped from 3 and 9 o'clock, I'm guessing there should be a small amount, is that correct, the rubbers looks in good condition.

Garry

Submitted by ian_soady on Tue, 04/07/2023

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... some float as little as possible is best. However, end float usually only casues problems with clutch drag as the first part of the travel just moves the whole lot sideways.

It could be that the link rod is slightly too long / short. I'd put in 3rd (making sure it's properly in) then remove the pins. They should slide in without having to move the lever on either end although of course you're limited to half a turn precision. You could replace the clevises with rose joints if you're not a stickler for originality.

Otherwise I'd be looking at rounded dogs.

Submitted by paul_standeven on Tue, 04/07/2023

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instead of looking at your over-weight pets.

More seriously, I would agree with every point you made. Checking the gear selection on that external link is the first step. If that is not an immediate cure, I would give the whole positive stop mechanism a good looking over in case there is lost movement anywhere, which can lead to loss of full engagement of gears. Another potential issue is the index plunger, directly at the bottom of the selector cam plate.  If that is not working properly you can get mis-selection of gears. It runs in oil, does not wear significantly, but could be faulty or loose.

Submitted by alan_hesslewood on Wed, 05/07/2023

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Speaking of over weight pets, does this remind you of anyone?

Les

"I knew the mother-in-law had been round because the mice had been throwing themselves on the traps"

My dolls head Model19 does the same. I`ve put better clevises on and the "dogs" look alright (not over weight and rounded) but still no different. Need a heavy paw to keep it held in gear!

Best regards, Al.

Submitted by garry_tyler on Thu, 06/07/2023

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Thanks guys for your help.. 

I have put the bike in 3rd and the pins do slide in and out easily without moving the arms, so that's OK. 

I have looked at the clutch more carefully and it's not in a good way, I will have to buy new springs, friction and steel plates. Also the spider is in a very bad way too with a LOT of slop on the splines, this is going to be replaced.. I also think that the mainshaft will probably need changing. So it looks like I'm going to have to strip down the box, see if there are any overweight pets or gremlins hiding..

Thanks again 

Garry

Submitted by paul_standeven on Thu, 06/07/2023

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is to check the gearbox end float.  This is set by a bronze thrust washer between 3rd gear  mainshaft pinion and the sleeve gear.  If it's worn, the shaft will move about, and reduce the clutch lift - that makes the clutch drag. It may also affect gear engagement, but it's more likely to affect top gear than 3rd.

Solution is a new thrust washer or put a steel shim behind it.

It would be worth a look to see if the worn splines are inside the clutch spider or the mainshaft.  Or both....

Paul

 



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