etz 251 ignition timing

[wrsni]

Stated timing is 2.5mm before TDC. Even with the points moved as far clockwise as possible on the back plate, the points are opening roughly about 5mm before tdc. I say roughly because I have a dial guage mounted in the plug hole but it only starts moving 3.5mm before TDC and the points have opened well before then.

I've moved the back plate as far clockwise as possible on it's mounting screws and checked the position of the cam on the end of the crankshaft and everything seems ok.

I'm completely stuck, any ideas please?

Thanks.

Oh, and the points are set at 0.3mm.

[mr_luke]

There's a thin pin which sticks out of the crankcase, and should engage with a slot cut in the edge of the alternator stator, so the stator is in the correct position. Check that the pin is engaged correctly and not bent out of the way or even missing.

[wrsni]

No, it's fine.

I have the back plate pushed as hard against it as possible (clockwise) but failing all else I'll have to remove the pin to allow the plate further round and therefore be able to obtain the correct timing.

Hoping I find something else first, but have checked everything I can think of. Just wondering if it's possible the cam can wear and need replacement or something like that???

[Guesi]

Hi

did you do anything else on this engine ?for example change the crankshaft ?
There are some reproduction cranks that have the small pin that holds the rotor in the right position is not exactly where it should be. So you cannot fix the ignition on the right timing...

[wrsni]

Unfortunately I have absolutely no previous history of the motorcycle nor am in a position to find out.

However the situation which you suggest would make a lot of sense and certainly tie in with my findings. Since my first post I've removed the rotor to make sure it hasn't slipped a bit or something like that but again, everything looks fine and exactly as it should be, the little peg on the crankshaft has no wear nor is there any wear on the rotor keyway. The only thing left to check is to find out if there are possibly slightly different cams and/or breaker points for different models and maybe something incorrect has been fitted to this bike in the past.

Failing that I'll just have to remove the locating peg for the back plate/stator to enable rotating it clockwise and hope that the three mounting screws are sufficient to hold it in place in future.

Thanks for the help.

[Guesi]

Hello

you also can remove the little peg on the crankshaft.
It does not hold the rotor in place, but is only to fix it in the "right position" when putting it on the crankshaft.
Without the little peg you can turn the rotor to the side you want .
It is held by the screw that holds also the cam.
And there ARE different cams. The one from the TS 250 is different from the ETZ one.And the TS 150 is different from both

[wrsni]

And there ARE different cams. The one from the TS 250 is different from the ETZ one.And the TS 150 is different from both

That's interesting, best way to check it out I suppose will be to try and source one genuinely for a 251 and fit it!

I'd have been inclined to move the stator back plate in preference to the rotor simply because it would have been easier to keep a check on but if it's the taper that secures the rotor anyway then removing the peg and shifting it a bit would probably be best.

Many thanks.