Author Topic: 51 douglas transmission  (Read 3888 times)

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Offline joe a

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51 douglas transmission
« on: 30 Apr 2007 at 02:21 »
hi, i have a 51 douglas that skips and binds(at times) in 2nd gear. does anyone know if this is a common problem, could someone fwd a photo of the transmission and where i could search for parts for the bike.......thanks,joe

Offline Doug

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Re: 51 douglas transmission
« Reply #1 on: 03 May 2007 at 01:24 »
Sounds like the clutch dogs that engage 2nd gear are rounded off. Also the peg on the shifter fork that engages the slot of the cam plate likely has a flat worn on it. This will result in some lost motion, and not pushing the second gear dog clutch fully into mesh. Then in conjunction with the rounded dogs, it is prone to jump out of mesh. Both can be inspected with the side cover of the transmission removed.

Good used gears and shifter forks are not getting any easier to find. You can get someone to TIG weld up the worn potions of the clutch dogs with manganese wire or even with Stellite (if not building up the corner too much.) The same can be done with the peg on the shifter fork, though it is much harder to machine back true when done!

-Doug

Offline eddie

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Re: 51 douglas transmission
« Reply #2 on: 03 May 2007 at 06:08 »
Joe,
       You should also check that the nut on the rear end of the layshaft is tight, as a loose nut will let the layshaft work its way forward if the front end is not correctly shimmed. You can get to the layshaft nut after removing the gearbox final drive. Also, with the side cover removed, check the depth of engagement of the dogs for 2nd gear and 3rd gear. If 3rd gear engages deeply and 2nd is marginal, removal of some material from the rear face of the layshaft bottom gear (this will require grinding) will improve matters as it will move the layshaft - and it's dogs - back, giving deeper engagement of 2nd gear. Finally, the front end of the layshaft should be shimmed up so that any forward thrust is taken by the bearing in the front cover, rather than relying on the rear bearing retaining plate.

                      Eddie.

 

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