Sticking Clutch

Hi people, I'm looking for a bit of technical advice. Sorry for such a long post but it might cover off some of the basics.

So here's the back story. I'm a mid-life-crisis guy who's just passed the direct access. In the weeks before my mod 2 test I bought a 2010 Sprint ST which went very cheap on ebay.

One reason it went cheap is lack of service history. It's done 43K miles yet has no service stamps at all. The owner (from new) stated it had never had valve clearances checked though oil had been changed. Other than the lack of some maintenance/history it's pretty well immaculate for its mileage and looks original and true.

I checked the valve clearances when I got the bike home, some bang on spec, all others well in tolerance.

I changed the oil for Castrol Power 1 4T (10W-40). I fitted a K&N oil filter and K&N air filter.

Two weeks later took my test, passed, jumped on and rode it .... First day I did 200 miles. Fabulous ride for the first 150 miles around the Peak District, never missed a beat, until …

Got bogged down in traffic around Macclesfield and after a couple of minutes the gears became stiff to change to the point I had to stop the engine. After a minute or so I could change them again and so rode on, but each time that I had to slow and repeatedly use the clutch the gears stiffened up and wouldn't change. This repeated the next day after only 10 miles or so. I found I could ride around the problem to some extent by pre-selecting neutral before coming to a stop at traffic lights etc and ‘rest’ the clutch.

It's basically the clutch not fully releasing with the lever pulled in and I'm guessing that sitting stationary for a while with it dragging is heating it and that's making it worse somehow. The cable is smooth in operation, routed correctly and adjusted to 1-2mm free play. Clutch engagement is smooth and progressive at about 3/4 released position. With engine off, bike on centre stand, first gear, clutch pulled fully in, the rear wheel is very stiff to turn by hand.

I trawled the www for a solution. It would seem to be a fairly common problem. It also seems many have tried various 'fixes' only to have the problems reoccur and I can find no one who has convincingly cured it even after buying lots of new parts.

So yesterday I removed and examined the clutch.

Clutch housing and baskets fairly clean with very little residue. Release mechanism, hook and pin barely worn. All friction rings are with good service life 3.8/3.9mm and 3.2/3.3mm and all steel rings are flat and look virtually un-worn. On pulling out the rings most were fairly well stuck together, it took a little finger pressure to pull them apart.

Their sequence (and I’ll add that it LOOKS very much like the three access covers have never been previously removed) was flat washer, spring washer, fat friction ring, then alternate steel/friction out to the final fat friction ring. The steels being 1.6mm for the first two, 2.0mm for the next four and 1.6mm for the outer three.

Now, the friction rings look quite dark in colour, particularly the pad material and the steel rings all look a bit cooked; slight blueing and generally very dark but evenly coloured.

I’ve used wire wool and brake cleaner to clean them all up and left the friction rings soaking in engine oil whilst awaiting new gaskets.

So here’s some questions;

1, Does it matter that the rings show signs of heating? It’s often cited that if they do they must be changed … is this true and if so can anyone tell me why? (They all appear to be perfectly flat, the clutch engages and drives well but the only problem seems to be that some rings ‘stick’ together when the clamp pressure is released)

2, The friction plates are stamped ‘FP-MN4-11’ and similar. Are these OEM parts?

3, Have I used the ‘wrong’ oil for this engine? (It states on the back of the bottle ‘Recommended by Triumph for all four stroke models’)

4, Does the sequence of 1.6 and 2.0mm steels matter? I suspect the order I found them in is as fitted from the factory but it does not match what others on various forums have suggested. I’m wondering this as the five staggered rows of oil holes in the inner basket might need to be exactly aligned with the rings; difference of 0.4mm ring thickness is not much individually but over the stack in the wrong order it throws it all out by some margin.

I’d best stop there before this becomes War and Peace!

Any gurus out there willing to offer their thoughts before I throw it back together?

 

Just this moment been reading that!

 

Cheers for the advice chuck. That may indeed be my first action but I see many before me have done that with no improvement. I'd like to try to understand why it's sticking in the first place though.

 

Cheers Smilinjack.

 

Quick update:

Spoke to Staffordshire Triumph, showed them the clutch plates and they suggested the steels look glazed with signs of overheating. I ordered a full set of friction and steel plates at £200 which are due in early next week.

What I don't know is whether the clutch plates were already cooked by the previous owner through poor adjustment or riding the clutch etc or whether there is another fault which has caused it. So I'm a little concerned about throwing a new clutch and gaskets on without knowing the original cause.

Guess I'll just have to ride it very carefully and stay local until I can be sure it's ok.

 

Pretty sure it's not an adjustment issue. The cable is fairly new, the in-line adjuster at the engine end is set around its mid-point and the lever is set with around 1mm free play. There is virtually no slack in the cable and the operation is smooth and free. The hook and release pin show minimal wear. Clutch disengagement occurs from around 1/3 of the lever movement leaving another 2/3 lever pull beyond that. It really looks to me as though some of the clutch rings are actually 'sticking' together after the pressure plate has been lifted. Having initially dismantled it and withdrawn the clutch pack half of the stack of plates could be picked up as a lump just by holding the end plate, the outer plates separated easily but those closer to the gearbox were progressively more stuck.

When cold or having ridden open road the gear selection is sweet and normal though there is always slight clutch drag. It's after sitting half a minute with the lever pulled in at a junction or off/on a while in slow traffic that it all starts to seize up. The clutch drags more and more and then gear change is impossible.

I don't have the experience with bike clutches to know what looks normal and what doesn't. Maybe the previous owner had left the oil in way too long and it's degraded and contaminated the pads such that they are prone to stick? Can that happen? I'll try to work out how to get a couple of photos up later to show you the colour and state of the bits.

Thanks for your advice everyone.

 

Ah cheers for that. I'll have a go when I get home.

 

Here's pics of the rings as best as I can get. Bear in mind they've already been cleaned with wire wool and brake cleaner.

 

Cheers Col_C, I had read that, and disappointed to see he apparently never solved it

 

That sounds positive. I've read up about soaking the friction plates in oil before fitting and also the filling with oil to soak them in situ. Neutral selection does seem to be the first to go in my case too. Almost impossible to find at standstill with engine running.

Re putting on centre stand, do you know if the clutch actually sits in oil on the stand? Seeing as I can take off the clutch cover without draining oil using the sidestand it looks marginal at best. But for the record it did sit for a couple of weeks on the side stand after I bought it and I do usually park it that way ...

Well, the new clutch rings come next week, I'll soak them overnight and throw them in and see what happens. Either way I'll report back.

Cheers for the input