Clutch Slip

[gazza]

Hi All
I have a lambretta Li 125 with 185 imola, 28mm carb,reed valve, MB revtour exhaust (only had the scoot a short time).
After experiencing clutch slipping got prepared to change the clutch, once it was stripped down discovered it to be a ' Billet ' style clutch which I was told shouldnt really slip.though I did notice that whilst riding I barely had to touch the clutch lever for it to slip. So on inspection noticed some 'witness marks' of rubbing on the inside of the side casing just above the clutch actuator. So taking a file carefully took some of the side casing away dri fitted and seemed OK. Put everything back together and also allowed a bit of play at the start of the lever and it ran and felt much better. Arranged a Dyno session and once it was on he told me that the clutch was still slipping and he showed me that the clutch is biting virtually at the end still and the play in the lever is just masking the situation.
Just wondering if anyone can shed some light or has any experience on this before I start to strip it down at the weekend. My initial thoughts are that the clutch assembly is jutting out too far, I have read bits on MB tech help about using a a 10mm packer between the casings but cant find one on his web site.
Also the clutch does not seem like the other Billet clutches ive seen/googled as it does not have a hexagonal spring retaining plate with 5 springs but has a square plate with 4 springs, one in each corner. I have googled this but have so far not been able to locate anything similar they all seem to be the 5 spring hexaganol type. Has anyone seen one before.
Many thanks

[DaveTomo]

is it this one?
http://www.saigonscootercentre.com/Prod ... =121&s_id=

[gazza]

Dave that indeed looks very similar I will know more when I take the side casing off at the weekend. Thanks that explains a lot Have you had any experience of these ? are they known to slip ? Really surprised as whoever had it previous has spent a lot of money on other stuff such as exhaust, Imola stuff, and a VHSH carb with 12volt variotronic.

[DaveTomo]

Gazza, can't really comment as I don't have that type of clutch ( I run a readspeed 5 plate, MB crownwheel & ScootRS spider, standard GP bell - race rapido 225), just from your description I guessed which one it was. Don't know if this will help or not, if it is that clutch , the developer uses a thicker gasket to get the space he needed.Hopefully someone will be along who does run one of those, good luck
http://scooterotica.org/forum/viewtopic ... ris+clutch

[gp200ts1]

I found with my Saigon billet clutch that when used with the gp style set up I had to grind back the casting on the sidecase where the bronze actuating bush sat as it was constantly pressing on the clutch. Also when used on an li type set up the thimble supplied by Saigon was too long and needed to be ground back slightly. A good clutch let down by all the fettling to set it to work properly. If you spend that sort of money you expect it to work straight out of the box!

[gazza]

thanks Dave for your help I'm a lot further on....And gp200ts1 these are the exact problems I'm having I've ground it back a bit in the same place u mention, and this cured the problem somewhat but I'm getting slip when I try to wind open the throttle just for a moment then it picks up... and was especially apparent on the dyno.
Once you had ground it back did you get any clutch slip ? My casing is supposed to be an LI but the stampings do look a little Iffy how can I tell the difference between an LI and GP casing ?
And did you also use a thicker side case gasket ?
thanks for the Help

[Toddy]

Have you fitted new plates since your modification ? usually if a Clutch starts slipping it means the corks are cooked and will need replacing so you wont see any benefit to your changes until you fit new plates

[Knowledge]

My casing is supposed to be an LI but the stampings do look a little Iffy how can I tell the difference between an LI and GP casing ?
And did you also use a thicker side case gasket ?

An Li casing and a GP/DL casing are identical, except for how they operate on the clutch centre. The GP/DL has identical operating arm (on top), shaft and actuating arm, but then it pushes onto a bronze bush with a diamater similar to a penny. This bush depresses the clutch centre, which has a flat top. The Li did not have a bronze bush, so the Li side casing does not have the support for the bush cast inside the casing. The actuating arm presses directly onto a removable nipple which sits in the centre of the Li clutch. Use google images to view different types of side casing.

Instead of sourcing a thicker gasket, fit two thinner ones. Just an idea.

[gazza]

Thanks for all the help and advice.
Toddy I think this clutch is a copy of an AF 5 plate race cassette type clutch and does not have corks, they are the steel type friction plates.
Well stripped it down tonight and sure enough after some measuring and the visable witness marks it is catching on the side casing, and also the kick start arm. Whilst in bits this time I decided to take the whole clutch out and examine the friction plates, 2 of them are quite worn with a small area on each really worn down i.e. no friction pads at all about an inch around the circumference.
Going to take them to scoot shop tomorrow to see if the plates are the same size as ordinary cork plates with the view to firstly swapping them. Then going to grind down the thimble on the pressure plate a bit to give more clearance to the actuator, and finally going to grind a bit more off the inside of the side casing which shouldn't be much, this along with either 2 or 1 thicker gasket should do the trick I will update once I have tried it out.
gp200ts1 do you know how much you ground of the thimble ? I'm thinking about 3-4 mm
Thanks again for the help

[gp200ts1]

3-4mm seems about right, I know it was probably around half of the thimble

[coaster]

Hope you don't mind me resurrecting this thread but I have just fitted one of these clutches to my TS1 engine. mine has a nipple in the centre of the pressure plate which suits my Li casing perfectly. However, whilst assembling it I noticed that one of the steel plates is 'dished' and not flat like all the others I went ahead and installed it and all seemed fine. The lever is the lightest I've ever experienced and it engaged and disengaged really nicely pottering up and down the drive. Out on the road it's a different matter, open the throttle in 3rd or 4th and the clutch slips like buggery as soon as the power band comes in, noticeably worse than the Reedspeed 5 plate it replaced. Just suspecting it's the dished steel as causing it, any thoughts or anyone hazard a guess as to the origins of the clutch plates?

Cheers

Colin

[gazza]

Hi Colin
I changed the plates in the end and put surflex clutch plates in, and I also found one of the steels was damaged, so went to a bike breakers yard and the guy there was very helpfull, he measured it counted the cutouts went through his manual and if my memory serves me right think they were the same as a KTM 50 motorcross bike,and luckily he had one in. After fitting this along with grinding about 5mm off the clutch nipple, and also fitting a thicker gasket, it worked ok for a few months but then started slipping again.
I've now given up and bought a clutch based on an Idea by a guy called Rocco its a 46 tooth crown wheel with an aprilla basket bolted to it with aprilla clutch plates and steels. It was built by a guy called 'the tarmac tickler ' I contacted him and he used it in his race scooters and said i'll never look back they are a great piece of kit.Just in the process of rebuild so I havent had the chance to try it yet but im hoping all should be good.
The vietnamese clutch is probably ok for standard engines but dont think it has the ability to cope with a tuned engine over a period of time.

[Vega125s]

Im still running a Rocco clutch , so light at the handle bar and never slips. Great bit of kit.