More TS125 woes

[ricklincs45]

Hello again Everyone,

sorry to be asking more questions, but having finally resolved the electrical issues on the TS, am now attempting to get her running.

Have 'almost' had her running, but seem unable to set the ignition timing correctly. The only place I can get the points to open is almost exactly TDC. The bike came with what I'm assuming were the original points, which are quite worn, and a brand new set of what I'm guessing are 'pattern' points. Can't get any different results with either set, so am assuming that either both plastic arms are too short to engage with the cam on the crank, or, the cam has moved somehow. Doesn't matter which way I move the backplate, the points will only open very close to TDC.

The only thing I'd say regarding the new, pattern points is that the fine wire that connects to one of the contact breakers is so long that there are massive arcs being generated due to it almost touching the cam/crank.

Have I missed something obvious, or would you suspect I have two sets of scrap points? If points are suspect, can anyone recommend a supplier of decent quality ones please?

Thanks for your time,

Rick

[therealche]

Have you set the maximum gap first? Rotate the engine until the points are as open as they will go then adjust so the gap is 0.3mm ( or 12 thou in old money) . I'll dig out a picture when Ive had me tea!

[therealche]

Contact breaker.jpg (65.88 KiB) Viewed 3609 times

Turn engine to give maximum opening of contact breaker
Loosen screw 4 then turn the eccentric 6 until the gap is 0.3mm ( or oddly Ive just noticed 0.4mm on the diagram)
Tighten screw 4
Then adjust timing by loosening 1 and 2 and moving the backplate

Then probably repeat!

[ricklincs45]

Hi, yes, did set the points gap first (thank you for including the pic' though). I've no reason to suspect the operating cam has moved, though will try and check that tomorrow.

The new 'pattern' points would seem to indicate that someone has tried to (unsuccessfully) fix this problem in the past. The nearest I've had her to running was with the timing adjusted to the very maximum clockwise rotation available - she ran for about 2 seconds and then cut out. Would have thought that with points in reasonable condition, the backplate would be somewhere near its central position when the timing is correct (give or take).

What I'm struggling to get my head around is why from one end of extreme adjustment to the other, neither set of points will time up correctly. No doubt something obvious is eluding me here...

[therealche]

Sounds very odd! The dynamo rotor should be keyed to the crankshaft, and the cam is keyed to the end of the rotor. I wonder of somone has lost the key between the rotor and crank and has just put it "about right" then tightened it up? It's easy enough to remove the rotor if you want to check

[DAVID THOMPSON]

i was thinking lost or sheared key
or if it was like a /2 bmw where the magneto magnet will slip when it loses grip on the tapered camshaft
dave

[ricklincs45]

Hmm. Have removed the contact breaker cam - it seemed to be located properly on its keyway, so no joy there. However, when replacing the securing bolt, it has stripped its thread at the very end, despite not over-tightening, so now have another problem. Here's hoping it hasn't damaged the crank thread...

May look at removing the generator - that seems to be the last option of things which may be mis-aligned. Any tips/advice for removal?

cheers,

Rick.

[therealche]

Oops! I doubt you have damaged the thread in the crank, it is much harder than the metal of the bolt. To remove the rotor find an M10 bolt 100mm long screw it into the rotor ( which has an internal thread just for doing this) hold the rotor in one hand screw the bolt in as tight as you can, then tap the end of the bolt and hopefully it will pop right off. there should be a little key in the crank ( a round peg IIRC not a woodruff key) While the rotor is off clean out the end of the crank and check the thread

[ricklincs45]

Thanks for that: just about to order a replacement bolt (and a spare..), and might go for a new set of points too (more out of curiosity to see if there is any difference between what I have) and see where it takes us.

Who would have thought getting a 'simple' two-stroke to run would be so, er, challenging

[therealche]

Maybe order one of the keys as well in case it's missing (looking at mzshop site it seems to be a woodruff key after all) and a new condensor always comes in useful

Thing is about buying an old MZ is that they tended to be ridden till they went wrong, then after a bit of ham fisted home maintainance, stuck in the back of the shed, until they decide they need the space.