When's a slipping clutch NOT a slipping clutch...?? :-/

[Donnie]

Scratching my head on this one!

I'd had a slipping clutch about 6 months back and once dropping the oil it was very obvious, stank of burnt oil etc. Replaced all the corks and the steels too and fresh oil and after adjustment has been good as gold until last night.

Went for a bit of a run yesterday evening with some mates and about halfway noticed that it was getting harder to get into neutral and was getting symptoms of clutch drag and so adjusted at the roadside and everything good until the next stop about 10 miles. Had a stop off for a shandy then headed for home, was fine for about a mile and then suddenly was losing power, but massively and this is 2 miles from home.

Now the symptoms were not like traditional clutch slip ie where the revs are increasing and the power doesnt come in at the same rate, it was more like when you miss a gear and get a real sudden increase in revs where you think it's gonna blow the top end! So, like that, I limped her home

Ive dropped the oil and it's black as pitch, it smells a bit burnt but Im thinking that was me slipping the clutch all the way home for 2 miles as opposed to it being stinking like a traditional slipping clutch :-/ (like it was 6 months ago)

So, has anyone got any thoughts on what would do this at all? The corks actually look ok believe it or not, but I will replace them with new, the springs look ok, there were a lot of metal filings in the magnet, but this had a new chain, new front sprocket, new steels in 6 months ago so probably that, no lumps of steel at all, chain looks good, teeth on both sprockets look good too and im just baffled

So any thoughts appreciated.

[Warkton Tornado No.1]

Lambretta clutches are weird (IMO) as the cable needs slackening as the friction plates bed in & the centre get s closer to the crankcase cover, & often that’s when the problems start!

I figure that you’re quite experienced & would have checked the obvious things like the top plate rubbing on the kick-start, steels or corks sticking in their slots & the thimble being soft as sh1te as a lot of readers have recently experienced....

I don’t suppose it is the thimble being short & the cam jamming either....

Could it be the front sprocket cush drive cam ‘going over?’ I had a 14 tooth Indian sourced sprocket once that allowed about one lap of Three Sisters before the transmission became ‘automatic’

[Donnie]

While you were posting I was back in the shed and checking the steels, all ok bar one that's burred the teeth but not too bad, I will replace it though anyway.

But yep all the rest including the thimble were spot on, then I followed the same train of thought as yourself, ie what else in the drive trains a possibility and led me to this



on running my finger on the edge it's sharp as a knife so definitely appears to be the front sprocket / cush drive.
I'll get that stripped and see if i have a replacement, pretty sure it's that and thanks for the reply it's always good to sound these things out with fellow scooterists.

[Donnie]

Hmmmm spot the difference

[Adam_Winstone]

This is the sensation of clutch slip that often gets me talking about front sprocket assemblies and the ramps riding one over the other... you now know the sensation and can see why so many people think that this is a clutch issue.

Whilst yours is a terrible example (or wonderful as examples go) of soft sprocket wear, this can also happen if you fit a SI spring by accident, if the sprocket has been machined too low or if the assembly is simply worn.

This photo may help others think about the issue whilst trying to think through the sensation of clutch slip that they suffer.

Adam

[Donnie]

exactly adam, and exactly why i took the photo for reference for others when they use the search function.

Now I need to decide what to do about my gear ratio but that's another thread im about to start in the tuning section.

[Warkton Tornado No.1]

That situation is a horrible thing to have happen.

Hopefully if you flush all the crap out, the other components will be alright.

You should be well placed @ Kempston to get a replacement, but if it can’t come quick enough, I’m happy to lend anything from 14 up to 19 tooth sprockets & Renold chains with all half sizes. All race proven but in Kettering.

[Donnie]

Cheers, Im going to flush it all out tonight while deciding on what sprocket combo to go for next
Dunno about being well placed in Kempston as nearest scooter shop now is Cambridge Lambretta since Bedlams have shut.

[johnnyXS]

blimey that sprocket is soft as butter to wear like that.! No prizes for guessing where it was manufactured.
looks like the metal hasn't been tempered correctly.... if at all.

I guess it probably started due to insufficient spring tension coupled with a powerful engine and aggressive throttle Was the spring new ?

[Donnie]

Not new but good. all innocenti and no marks on the other cush parts or sleeve at all.

[johnnyXS]

Not new but good. all innocenti and no marks on the other cush parts or sleeve at all.

mmm call me a cynic but I'm surprised at the wear pattern on that part if it was properly tempered steel. The fact that there wasn't corresponding level of wear on the opposing part speaks volumes.

I suspect there are many pattern parts being cast in the Far East with Innocenti markings . Outwardly there is no way to tell really except for the poor casting and finishing.
Same as clothes ....when was the last time you were sure you had bought some pucker levi 501s

[bazza3004]

Hmmmm spot the difference

Is it a camera angle thing or are the two sets of teeth all to cock as well . They look closer together on one side than the other.

[a.lo]

Hmmmm spot the difference

Is it a camera angle thing or are the two sets of teeth all to cock as well . They look closer together on one side than the other.

the flat end don't look to clever either

[Donnie]

Yeah the flat end was well worn too, so theres no way this was hardened, as for it having innocenti markings it didnt, its aftermarket but obviously a shoddy one.
when i looked at it again one of the teeth was cracked and with a small squeeze i was able to dislodge it completely falling off in my hand!
as for the teeth rows being together on one side, thats the close up of the camera distorting the picture, ive checked

As for the levi's? I've never been able to spend upwards of 50 on a pair of jeans, never had them, never will.