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Clutch slipping then stuck on

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

Clutch slipping then stuck on

Postby Jeff t » Sun Jun 19, 2022 8:38 am

Set off on a run and stopped a couple of times and when I kicked over it felt like the clutch was engaged but started maybe after three or four kicks. We then set off and the clutch started to slip really bad so pulled in and the clutch was fully engaged and wouldn’t start five of us there and some really Lammy experience. When we kicked over the flywheel wasn’t turning or if it did only slightly and every now and then. It was obviously hot and we had done about 60 miles and I had been out twice before since I’d rebuilt it, one about 50 mile run. Eventually got recovered but even 24 hours later there was no change it still appeared to be stuck on.
I’d had it dynoed and the old clutch was slipping so I had just rebuilt the clutch with the standard cluch spider but 5 plate clutch, the lever clutch lever was working and the the spring was pushing the arm back so that wasn’t stuck. Stripped it down yesterday and the oil stinks and clearly burned clutch plates, I have searched on here for help and the crush drive and sprocket all good. I have rebuilt everything and with the clutch compressor all seems to work ok. The only thing I didn’t check when I stripped down was if the springs were located correctly. I can’t see any obvious issues with the clutch spider and will check the rear sprocket again after just reading Sticky’s book.

Any ideas?
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Re: Clutch slipping then stuck on

Postby coaster » Sun Jun 19, 2022 9:22 am

Your terminology is a bit confusing. you say is 'stuck on' but Im guessing you mean that it is slipping without the lever being pulled? It does sound as if you have burnt the clutch out possible due to it being over adjusted. 5 plates in a standard basket will usually result in not enough seperation between the plated when the clutch is fully operated. You need to measure this when building your clutch using the clutch compressor to fully compress the assembled clutch and them using feeler gauges to measure the clearance between the friction discs and plain steels. This needs to be a MINIMUM of 1.5mm and you will uaually need to fit special thinner steels plates to achieve this. You will also find that the clutch 'pack' is still too thick to fit fully within it, the top plate 'ears' might not actually be engaging, the ears on the bottom pate need bending up and the top plate bending down.

If you havent already bought it, Stickies book is a MUST have, it expains all this ;)

Last point, you didnt say what engine spec you are running, if its less than a 225 then a 4 plate standard clutch is usually fine.
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Re: Clutch slipping then stuck on

Postby Jeff t » Sun Jun 19, 2022 10:17 am

Thanks it’s 200 small block mugello, when I stopped and tried to kick over it was as if the clutch was fully engaged. I even took the trunnion out of the clutch arm and it made no difference
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Re: Clutch slipping then stuck on

Postby MickYork » Sun Jun 19, 2022 10:30 am

Are the ears catching on the kickstart area ? How loose are the plates in the basket (some plates need filing) ?

I built a 23hp engine and tried a 5 and a 6 plate clutch, nowt but problems. I eventually used a standard 4 plate with LTH plates (about £20) and Malossi springs (about £10). Nice soft clutch and close to 20k miles.
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Re: Clutch slipping then stuck on

Postby coaster » Sun Jun 19, 2022 11:47 am

Jeff t wrote:Thanks it’s 200 small block mugello, when I stopped and tried to kick over it was as if the clutch was fully engaged. I even took the trunnion out of the clutch arm and it made no difference


When the clutch slips the corks get hot and expand. With 5 plates in a standard basket it will not take long before they swell enough to take up all the slack between the plates. When it cools down in most cases all will be fine again.

A small block 200 should only need a standard clutch tbh, maybe a set of good quality standard springs or uprated ones if you dont mind a heavier lever action. Its also possible that the springs in there now might be weakened having been overheated.

I have spent many hours messing with 5 plate clutches (REEDSPEED) and would often take 5 or 6 attempts at mixing and matching combinations of thick and thin steels and sometimes had to resort to using one or two worn corks to achieve the 1.5mm clearance. I took the last one out after I discovered that the top plate had been spinning :? 5 plates really need a deeper basket tbh.

PS, I've had AF cassette clutches in my Avanti 225, TS1 225 Grand Tourisimo 200 and 240 with no slip or drag whatsoever
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Re: Clutch slipping then stuck on

Postby Jeff t » Sun Jun 19, 2022 12:40 pm

Thanks for the replies and looking at the rear sprocket it’s rigged where the clutch ears locate so maybe that. Also if the plates are two thick wouldn’t it have the opposite effect and drag rather than slip?
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Re: Clutch slipping then stuck on

Postby L111amo » Sun Jun 19, 2022 3:41 pm

Had this problem a few years ago when we we to Normandy, intermittently wouldn’t start & kickstart when to floor as if clutch lever was partially pulled in, stripped out clutch & found the lugs were digging into spider / catching so to give the effect of clutch partially engaged, filed out as temp repair, was ok for 2 more days & trip back to brim; then fitted whole new clutch. All been good & just been back to France again with no problems
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Re: Clutch slipping then stuck on

Postby coaster » Sun Jun 19, 2022 10:19 pm

Jeff t wrote:Thanks for the replies and looking at the rear sprocket it’s rigged where the clutch ears locate so maybe that. Also if the plates are two thick wouldn’t it have the opposite effect and drag rather than slip?


Im still confused exactly what the issue is, I thought you said it was slipping when kicking it over but then after a ride the clutch wouldnt disengage (you said 'stuck on') :?
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Re: Clutch slipping then stuck on

Postby Jeff t » Mon Jun 20, 2022 8:47 am

It was slipping when running and progressively got worse when I stopped it wouldn’t start as though the clutch was stuck on
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Re: Clutch slipping then stuck on

Postby alex_hughes » Mon Jun 20, 2022 12:22 pm

by 'stuck on' do you mean it's like the clutch lever is pulled in? even though you are not pulling it in?
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Re: Clutch slipping then stuck on

Postby Jeff t » Mon Jun 20, 2022 12:28 pm

Yes exactly that
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Re: Clutch slipping then stuck on

Postby hullygully » Mon Jun 20, 2022 1:20 pm

have a looksey @ your cush drive on your front sprocket bud, mine was acting like that all the way from Whitby one year, it got steadily worse & was down to 15mph @ the Hull border control, mine was made of cheese, a non-Innocenti one :(
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Re: Clutch slipping then stuck on

Postby coaster » Mon Jun 20, 2022 6:35 pm

Jeff t wrote:Yes exactly that


So the lever is floppy? if so then thats a definate sign f an over heated clutch. The slipping makes it hot so the plates expand and lock the clutch up. When it cools down it would probably go back to slipping
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