AMC - Clutch

OEW591 · Post by **OEW591** » Fri Apr 24, 2009 9:32 am

The clutch on my 1958 Model 30 is driving me to distraction and I'm beginning to think the fault may actually lie in the gearbox perhaps some of you learned gents could offer some thoughts:

All the plates are new, there are no burrs on the clutch centre or the chainwheel. The bearing race is new and there are new cush rubbers fitted. The pushrod is the correct length and new.I have set the pushrod adjustment as per the manual and then adjusted the cable free play to the correct tolerance. The action is extremely light and there is no "clunk" into first gear.

Everything appears fine until I have covered around ten miles at this point the cable free play starts to increase and the clutch will start to drag slightly. The free play then increases to a maximum of about 1/4 of an inch and then settles at this regardless of how far or how hard I ride the bike. Obviously with this amount of free play the clutch drags.
If I then leave the bike for a few hours or overnight, the free play reduces back to the correct tolerance or if I adjust the cable whilst the bike is hot, once cold there is no free play and the clutch will slip slightly when pulling hard.

I can find no fore and aft movement in the mainshaft but I have only tried this when cold and I can't see any obvious cause for this "creeping" cable play.

Any ideas?

Eric · Post by **Eric** » Fri Apr 24, 2009 10:05 am

This is only a thought but it seems that getting things warmed up maybe at the root of the problem?

Does the gearbox or primary chaincase seem to be abnormally hot?

I do realise it maybe difficult to say what is normal without comparison to another bike.Edited by - Eric on 24 Apr 2009 09:06:43 AM

SPRIDDLER · Post by **SPRIDDLER** » Fri Apr 24, 2009 10:38 am

It does seem that something is swelling when warm and creating the slack - cush rubbers? Clutch friction material - corks?
Is the new pushrod perfectly straight and sliding freely within the mainshaft? - I appreciate that it will not be easy to check this since the problem seems to occur only when the whole gubbins has warmed up
It's worth being aware that even 'new' pattern parts can be wrong...

kernow kid · Post by **kernow kid** » Fri Apr 24, 2009 11:20 am

Hi, for what its worth, Id be very surprised if the fault lay with the gearbox.
Its not unusual for any clutch assembly to swell as it warms up, but yours does sound quite extreme! I would agree with Spriddler about questioning the origins of the clutch friction plates and their materials. Also, what oil are you using in the primary drive housing? There are many posts on here as to what works best but it would be interesting to know what youve used.
I have found that adjusting the clutch basket spring tension can be quite important. Rather than just screwing the 3 top hats over the springs down to the same level, I needed to adjust each one to end up with an even lift of the plates, when viewed from the side of the basket. With the primary chain case off, do the plates lift evenly?
Regards KK

OEW591 · Post by **OEW591** » Fri Apr 24, 2009 2:30 pm

Hi Guys thanks for the replies.
"cush rubbers? Clutch friction material - corks?" - The rubbers were purchased new from JSL along with a complete set of plain and friction plates and the pushrod. The original friction plates had cork inserts.

I have used JSL springs, "Norton" springs from RGM and the originals but every time I've replaced something the problem has returned within ten miles.
The bike has had the problem since I bought it and I have renewed everything except the clutch basket and centre (even the nut and spring washer!)

The pressure plate lifts squarely and the plates appear evenly separated (when cold) and the handlebar lever action is very light, lighter even than a B52 clutch.
Pushrod rolls "squarely" on plate glass (original was cut in two with a ball bearing between the halves)and runs cleanly in the mainshaft when cold.
Spinning the whole assy (without the chain) also shows no eccentricity or wobble.
The primary case seems no hotter than my G12 but I haven't actually measured the temperature with a thermometer.
I use GTX in the primary case (I use this for all my bikes and have had no other problems) but just to experiment I have used Ford ATF, which the Enfield boys swear by, and had exactly the same problem.

Something is obviously swelling due to heat but I must admit I'm at a loss.

kernow kid · Post by **kernow kid** » Fri Apr 24, 2009 3:02 pm

That seems like most angles covered! Im intrigued at how light the lever is though. My 62 650 CSR and fathers 59 350 both require/required what I would call noticeable pull needs at the lever but not enough to cause arm pump or fatigue.
Is it the 3 spring or 5 spring assembly?
I cant think of any part of the gearbox mechanism that could cause this with heat.
Primary chain tension all OK? Its possible to (carefully!) run the engine with the primary chain cover left off, just to make sure everything is aligned and spinning around as intended. I wouldnt ride it down the road like that though!
Has someone slipped in an extra plate somewhere? Are you happy the clutch assembly is as standard?
Regards KK

paul knapp · Post by **paul knapp** » Fri Apr 24, 2009 4:23 pm

I think your problem may lay in the spring tension being to light. Try re setting them for a much firmer pull on the lever.

OEW591 · Post by **OEW591** » Fri Apr 24, 2009 5:10 pm

I'll try tightening up the springs.
I have adjusted the nuts to be flush with the front edge of the pressure plate, which I was told by various AMC gurus is their correct tightness and as I've said, when cold, the clutch does not slip or drag so I would have thought the adjustment must be somewhere near correct.
Oh well off with the exhaust pipe and footrest again!
Thanks for the advice guys.

itma · Post by **itma** » Fri Apr 24, 2009 5:13 pm

all this would seem to start from the clutch push rod but I can't see how unless someone has done something daft like fit an alumiiniun one which expands.

Don Madden · Post by **Don Madden** » Fri Apr 24, 2009 7:06 pm

I would carefully compare your clutch with the book for the early AMC clutch, which your 1958 should have. Other than the plates, which are reversed from the later on whether the tabs in in the inside or out, parts are very scarce for the early type. Clutch basket & back plate are different. As these parts are hard to find, I've found mixed ones in clutchs over the years.

There are also 3 different pressure plates, a deep one for 3 plate clutches, shallow for 5 plate & one in between for the 4 plate.

If all parts are correct, adjusting the nuts for the annular flange to be even with the pressure plate is correct & with the correct levers with 7/8in spacing & all adjustments correct, the clutch should be an easy pull. I can pull mine with one finger if I work at it & two easily.