roundcase gearbox explained, please

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stian buksa
Cucciolo - the Lil Pup
Posts: 20
Joined: Mon Oct 12, 2009 11:50 am

roundcase gearbox explained, please

Post by stian buksa » Sun Oct 18, 2009 2:24 pm

Im having a weird problem with my -71 GT
Whenever Im engaging 1st gear the bike gives a yank after 1 or 2 seconds, as if the gears suddenly falls into place. It stays in gear all the time.
I've checked the selector box and everything looks ok. The shaft between the selector box and the gearbox is slightly worn, but doesnt give any free play
Now I have split the engine, and to me everything looks ok. But none of the manuals I have states what gears engage when 1st speed is chosen, so I cant really check it out
Does anybody know where I can get an overview over what position the different gears are in in the different speeds ?
Preferably downloadable.

Stian, Norway

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abmartin
SSD900 Darmah
Posts: 358
Joined: Tue Apr 10, 2007 5:08 pm
Location: New Brunswick, Canada

Post by abmartin » Mon Oct 19, 2009 7:04 am

Hi Stian,

Could it be a clutch problem rather than a gearbox problem? You also should make sure that the gearchange return spring is in good order and the pedal is properly centred. Lurching and hesitating when engaging first gear is not unknown with Ducatis and if it only happens occasionally may not be a cause for serious concern.

Bruce
1979 900SS
Fredericton, NB
Canada

machten
MHR / S2
Posts: 480
Joined: Sun Oct 29, 2006 8:37 am
Location: Perth, Western Australia

Post by machten » Mon Oct 19, 2009 7:57 am

Hi Stian,

So when you say that after 1-2 secs you get a lurch, that sounds to me like you are not quite enaging properly on gear shift. If that is the case, it could well be in your selector box setup. Have you tried adjusting the selector adjustment screw behind the gearshift lever?

Kev

wdietz186
Cagiva Alazzura
Posts: 703
Joined: Sun Sep 10, 2006 5:40 pm

Post by wdietz186 » Mon Oct 19, 2009 1:12 pm

Sounds like the clutch plates are hanging up on the hub or basket keeping the clutch from engaging fully. This is usually caused by grooves/notches on the clutch drum splines. Take a close look at the components.The push rods through the mainshaft can also hang up too and delay full engagement.If the dogs and the shift forks are in good condition it is unlikely a problem in the gearbox.

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Steve Foster
Parallel Twin
Posts: 141
Joined: Thu Dec 07, 2006 2:43 am
Location: Sydney, Australia.

Post by Steve Foster » Tue Dec 08, 2009 3:29 am

Hi Stian - in response to your question about getting an overview of the position that the different gears are in see the following article

http://www.dinamoto.it/DINAMOTO/8_on-li ... io_eng.htm

If you look under the section "Transmission with meshing gear" you'll get a good idea of how the 750 GT gearbox works with the main shaft above the lay shaft.

Hope this helps,
Cheers,
Steve.
1974 Ducati 750 GT

stian buksa
Cucciolo - the Lil Pup
Posts: 20
Joined: Mon Oct 12, 2009 11:50 am

Post by stian buksa » Thu Jul 15, 2010 1:18 am

Finally finished my rebuild, and it seems that Machten was spot on and the gear selector box was badly adjusted

Works like a charm now :-D

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