MZ/MuZ Riders

Good day to you all.

I am now just one step away from getting my 1979 TS125 back on the road.
The final problem is a dragging clutch.
I have put the correct oil in, to the correct level, and adjusted all of the free play out of the cable (on the understanding that some free play should be put back in before I ride in earnest).
However I cannot engage 1st gear without the bike stalling or moving off.

Today I took a short ride to see if this improved.
I must say the bike goes very nicely for a 125cc. It whips up to speed no problem and I can get all 4 gears.
But the dragging clutch remains.

Does anyone have any thoughts about the cause?
I have measured the travel of the actuator rod and it is just 1.2mm.

Does this sound enough?

I have checked the clutch basket for wear or notches and I think it is OK.
I have some aftermarket levers on the bike and wondered if the cable pull was not enough. They are TS levers, but reproduction ones. Comparing with the one original lever I have, I'd say they are very comparable though.

Thanks.

bent lever caused me problems1967 to 70 on 1966 yamaha YM1 not pulling cable far enough

I also had a ts125 with the same difficulty adjusting between a dragging clutch or a stalling engine when hitting first gear.
However this was only a problem when first starting from cold. After a few hundred yards the clutch worked normally, so my solution was just to make sure i had a clear road ahead before leaving neutral for the first time. Does your clutch continue to drag when the engine is warm?
I had another ts125 with no such problem.

Great suggestions. Thank you.
The levers are new, so not bent, but of course that doesn't mean they are correct.
I am seeing about 18mm of cable pull which sounds on a par with Puff's ETZ.
But I agree this doesn't translate into much motion at the clutch with just 1.2mm of throw.

It's almost like the lever is too long at the clutch end.
If I had a spare I'd shorten it just to prove out the theory, although this would be addressing the symptom and not the cause.

It sounds like a warm engine test is needed.
I'll find a quiet day and give is a proper test ride and report back.

Thanks.

I agree with the others.

But seriously I think you need a ride. And just a few times around the block doesn't really suffice. You need to be out for at least half an hour I'd say, and conclude some results after the oil has got warm.

Unfortunately I don't know much about the 125/150 model MZ's so I really can't help you in regards the clutch mechanism, sorry.

Hello again.

Following a good run out just now, I still feel the clutch is not right.
I rode for a good many miles and the engine was pulling well and sounding right, but the clutch (although improved) still seems to not release enough.
The symptoms when warm, are that if you pull the clutch in to coast, the engine revs don't drop; there must be enough drive through the clutch to keep it running with the wheel speed.
All the gears are a bit crunchie unless you match the engine revs with the wheel speed. I accept this is good practice anyway - but I think there should be more flexibility in the system.
At one point I stopped at some traffic lights in second gear and couldn't get into neutral or first.
I had to pull away momentarily in second to get the wheels rolling and was then able to down-shift to first to move off properly.
Towards the end of the ride I took all the free cable play out of the system with the cable adjuster at the lever, but without any noticeable improvement.

I'd appreciate any other thoughts.
In the meantime I will go through the system and look for sources of free play and/or wear.
I am beginning to think that the 18mm of cable pull is OK, but that I am losing motion somewhere else.

Cheers,
Steve.

Reading this, I have just remembered what I found when first investigating the draggy clutch on my TS125 after the first ride. The clutch assembly had been fitted to the gearbox input shaft incorrectly, there was a large diameter washer between the whole assembly and the bearing. This meant that when the clutch centre nut had been clamped down, the load was taken from clutch centre bush to bearing OUTER race! Obviously, this washer had ground down and deformed (there was a lot of metallic swarf in the oil) to allow the clutch assy to spin freely. As it had ground down/deformed, it had created a clearance between centre bush and gearbox input bearing, which was allowing the whole clutch assembly to float on the splines by about .5 - .75mm, completely messing with the clutch throw. Although it was just about usable, the clutch felt very strange and dragged terribly. I can't recall if you've had the primary cover off to have a look, but it might be worthwhile just to have a check in there.

Thanks for the continued support.

Puffs - I normally do select neutral before stopping on my old bikes, but on this occasion had to stop suddenly and didn't have time to find it.
I agree it is the better way to ride though.
The numbers you provided on clutch plate thickness looks useful - I haven't checked that.
I will also check how far I can push the actuator rod before the springs are fully compressed - just to make sure it's not running out of travel.
I think the cable is OK. It's not new, but the 18mm was measured at the clutch end (albeit without the load of the clutch working against it).

Throwley - that is an interesting description.
I have had the whole engine apart and re-shimmed as needed. I try to work methodically, but there's more than a good chance I have put something back wrong.
I haven't noticed much end float on the clutch basket but I will look again.

I looks like I should take the clutch cover off again, then I can measure the clutch plates and also check for the washer issue described.
That should keep me busy for a bit

Cheers.

Curious, have you replaced the clutch friction plates?

At least on the 250 models, each new cheap aftermarket plate (made in Taiwan) is around 0.3mm over thick, so five of them makes a considerable difference to overall clutch usage- trust me, I know- I installed some many years ago and found the clutch very tough even as fully pulled in as possible, and dragging like mad. Obviously, such individual items were so thick that even on full opeartion not enough gap was given to have the plates move (except perhaps 100,000 miles of usage might wear them in a bit!) The bike differed in neutral vs in gear/w brake applied by about 300-400 rpm I seem to recall.

Nowadays I lathe the clutch plates down and have no trouble, but Puffs mentions plate thickness, and you say you haven't checked- so I would definitely check them against stated specifications in the manual!

Thanks Blurredman.
I will remove the plates and measure them.
I didn't replace them, they are old and I don't know what happens to unused clutch plates if they have been left standing.
I will also check them on a flat surface, and if in doubt, renew them.
Cheers.

An update this evening.
I was observing the clutch plate movement whilst operating the lever and noticed that the motion started off OK but towards the end of the travel, one side of the clutch plates stopped and the other side continued to move.
To put it another way, the plates separated in a parallel way at the start but then one side stopped, leaving at least some of the plates at an angle and feeling tight in the clutch basket.

I have pulled the clutch plates and measured the thicknesses, and also tried to measure the OD and the length of the engagement teeth.
Then I tried each plate on its own to see how freely it moved in the basket.
The results were..............



There seems to be a correlation between the larger diameter OD and the sticking plates.
In addition I checked each tooth on the plates in the basket slots individually, and they seem OK.
However the other observation is that the sticking plates were much worse at the outer end of the basket.
All the plates were free to slide further into the basket, but some became tight as I pulled them out.
I think this suggests that the basket is very slightly conical, causing some plates to be tight towards the outer edge.

However the other obvious thing is that all the plates are above the thickness tolerance given by Puffs.

My options are to rebuild the clutch selecting their positions according to their OD, with the larger ones closer to the inside where things are a looser fit.
I may do this and re-observe the clutch motion to see it is is improved. This will cost me nothing but some time.
I guess another approach might be to file diameter of the sticking plates to make them a looser fit?
I expect I will end up renewing the plates anyway - but it would be nice to prove if everything else is OK or not.

Interesting outcome and conclusion. I would indeed try placing the larger discs where they are most free and go from there.