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Clutch basket/crown

Technical help for Series one, two and three Lambrettas. Models include the Li, Li Special, TV, SX, GP, Serveta and API/SIL models

Clutch basket/crown

Postby Stapsie » Tue May 15, 2018 11:05 am

Hi, I'm rebuilding a gp150 engine with some new and old parts and I have a problem with the clutch build.
Using a new rear sprocket/crown wheel and basket, when tightening the centre nut the basket will not spin freely on the crown wheel. It is fine until the nut is tightened.
The chain does still move freely around both front and rear sprockets. Any ideas as to what to check please. New bearing used throughout. Thanks.
Last edited by Stapsie on Tue May 15, 2018 6:27 pm, edited 1 time in total.
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Re: Clutch basket/crown

Postby drivera » Tue May 15, 2018 11:18 am

The shim behind the clutch basket comes in varying sizes from 0.8mm to 1.8mm , try measuring the one you have and if large go down a few sizes ,
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Re: Clutch basket/crown

Postby Toddy » Tue May 15, 2018 12:14 pm

is it an original Rear Sprocket or a new one ?
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Re: Clutch basket/crown

Postby Stapsie » Tue May 15, 2018 12:23 pm

Cheers drivers, will have a look at the shim when I get home.
Hi Toddy, it's a new one but did try the old one and it's the same?
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Re: Clutch basket/crown

Postby Stapsie » Tue May 15, 2018 12:24 pm

Sorry Drivera, should have gone to Specsavers.
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Re: Clutch basket/crown

Postby drivera » Tue May 15, 2018 2:26 pm

Stapsie wrote:Sorry Drivera, should have gone to Specsavers.



:lol: :lol: :lol: :lol:
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Re: Clutch basket/crown

Postby Stapsie » Wed May 16, 2018 10:49 am

Just checked the shim, it is 1.4mm thick. Will get a thinner one to try.
One thing I have noticed is that the shim isn't flat. It's grooved around its diameter giving it a variation in thickness depending on where you measure. Hopefully a new flat one will help. ;)
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Re: Clutch basket/crown

Postby HxPaul » Wed May 16, 2018 2:47 pm

It sounds like theres something wrong with the gear cluster or endplate bearing,or if one or more loose gears have been assembled the wrong way around it will give that symptom.By the way,the shim behind the clutch should be flat.
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Re: Clutch basket/crown

Postby coaster » Wed May 16, 2018 4:08 pm

I don't have it to hand at the moment but doesn't Sticky's book mention the various hieghts of the boss on the back of the sprocket? I've had similar trouble myself in the past.
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Re: Clutch basket/crown

Postby Toddy » Wed May 16, 2018 4:11 pm

coaster wrote:I don't have it to hand at the moment but doesn't Sticky's book mention the various hieghts of the boss on the back of the sprocket? I've had similar trouble myself in the past.


That’s why I asked if it was a repo one I’ve had similar issues
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Re: Clutch basket/crown

Postby HxPaul » Wed May 16, 2018 4:35 pm

The clutch sprocket must sit just lower than the spider,if it were the other way around when the centre nut is tightened the rear sprocket would lock up and not move.The OP says that when the centre nut is tight he can still move the chain and sprocket combination.
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Re: Clutch basket/crown

Postby Stapsie » Wed May 16, 2018 5:04 pm

Thanks for the info guys, I will have a look tomorrow and see what I find. I will get a couple of new shims and have a play. Local supplier just a few minutes away. Cheers.
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Re: Clutch basket/crown

Postby holty » Wed May 16, 2018 9:44 pm

as hx paul has said the spider needs to protrude out of the rear of the crownwheel slightly, if it is lower then it will lock, either try another spider that is longer or you might be able to linish the rear center of the crownwheel enough to get the spider protruding, ive used an oilstone in the past, press it onto the stone and turn, and keep turning to rub it down evenly, can take a while but does solve the problem,
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Re: Clutch basket/crown

Postby Stapsie » Wed May 16, 2018 10:26 pm

Cheers holty, something else to have a look at, tomorrow hopefully.
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Re: Clutch basket/crown

Postby Fat Trucker » Thu May 17, 2018 2:45 pm

Stapsie have you tried the spider on its own? When you changed the bearing did you use a new circlip?
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Re: Clutch basket/crown

Postby Stapsie » Thu May 17, 2018 7:23 pm

Hi Fat Trucker, not tried the spider on its own but will, cheers. I used the old circlip when I changed the bearing.
Got a new shim today so will have a go tomorrow. Can't get out to the shed tonight. Thanks.
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Re: Clutch basket/crown

Postby drivera » Fri May 18, 2018 5:21 pm

drivera wrote:The shim behind the clutch basket comes in varying sizes from 0.8mm to 1.8mm , try measuring the one you have and if large go down a few sizes ,



Ignore what I said about the shim its bo**ocks , after checking mine it's as Toddy and others have said , it's the clearance between the clutch spider and the crown wheel , all the shim does is line up the crown wheel and front sprocket
DOH !!!
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Re: Clutch basket/crown

Postby Stapsie » Fri May 18, 2018 5:57 pm

Got it sorted. A new shim was tried and it's worked. The spider now spins freely independently from the rear sprocket.
The old shim had grooves worn into it which meant that the spider and sprocket were at different levels. The whole clutch was well worn and being replaced but I assumed that the shim was ok. doh! :oops:
The joys of Indian scooter projects.
Thanks for all your help guys, much appreciated. And thanks for the shim Warren.
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