Damn, bloody points vexing me!

[Blurredman]

Hi there guys.


Recently got a really poorly H reg (1990) ETZ251.

The piston and barrel were seized but I have temporarily put on it a barrel and piston pair that I had spare.

The electrics have all been pretty much sorted (to a road MOT test level anyway- Pass light and pilot light don't work- but that's due to poor connections). Had to use 1 round indicator and round brake light from my box of bits. Frankenstein's monster kind of bike.

The only thing stopping me now other than replacing the original Pneumant tyres is to sort out the timing. It has points and I have put on a new set however the problem arises after I adjust the gap to 0.3mm, I take it to about 3mm before TDC and I cannot adjust the timing sufficiently to get the points to open at all!! I have even used the stator cover and lobe from my perfectly working ETZ250 (Coincidently today it's being SORN'ed in preparation of the new daily hack), and But even that presented me with the same issue! Obviously this stops any spark from happening.

If I adjust the timing to just open at the appropriate time then the gap is 3-4x larger than what it should be. I just don't understand. I've tried to angle the generator cover to see if this can resolve it but it doesn't achieve enough angle. The problem persists regardless of how much angle I try and purchase.

If there isn't an obvious reason for this, my only option is to use electronic ignition which I agree is an advantage in general running and persistent firing, but when the bike is being used every day I would rather have a points fail on me but still have a spare with me in my box than be stuck on the road because the electronic sender has failed, if you know what I mean.

However, I agree that is unlikely so I am still open to that if that is my only option open.


Can anyone help here? It's the last thing stopping me from riding it to the MOT station..

[DAVID THOMPSON]

Is the cam the points run on ingood shape
And make sure all the pieces are the correct stuff
Dave
My 2 smokers were a HD hummer (DKW RT125CLONE)really bad clone
AND a yamaha 1966 ym1 305 cc 2 stroke
So not to many

[Blurredman]

Like I said, I even took the stator and lobe from my well working ETZ250 but have exactly the same problem.

[den]

im pondering for you , because the issue is being illogical its hard to apply logic to understand it, so we got to think outside the box,
have you put a screwdriver in the sparkplug hole to manually find TDC and does it relate to the stamped TDC on the flywheel.
have you put a vernier gauge on the cam lobe to reference its size to your other one,
have you looked at the keyway on the cam and magneto shell,,you'll loose a mill if that's worn.ie , your TDC reference will be out,
anyway , if im pissing in the wind forgive me,,its sunday morning, keep us updated

[DAVID THOMPSON]

working on a bike that may have had several dozen owners
can be a real pain

[breakwellmz]

Like I said, I even took the stator and lobe from my well working ETZ250 but have exactly the same problem.

I can remember a mate of mine having the same problem with an MZ 125 many years ago, it turned out he was trying to set the timing to 3mm after TDC!

[keleto]

I actually have a similar issue. I have got the ignition firing perfectly at 2.5mm BTDC with a home-made dial gauge. At and around TDC the gap is perfectly fine at around 0.3mm, THEN after starting to close up the points whack open to about 4mm wide for about 1/4 of the whole cycle. (I can post a video if anyone doesn't believe me !!). The bike is a late ETZ251 which was converted from electronic to points at some time. God alone knows what MZ the points cam came off but it seems in good condition. The points cam is properly located on its tang, the stator is properly located on the crankcase pin and the rotor is properly located on its crankshaft peg. If anyone can advise me (and the original topic poster) I would be grateful. It runs fine but this configuration must be putting a lot of wear on the points heel and strain on the spring.

[breakwellmz]

Sounds like a bad batch of points cams.

[keleto]

A more experienced friend had a look today and noticed that the **whole rotor** was slightly eccentric. He suggested that either the rotor was slightly ill fitting on the taper or that the crank was out of alignment after a new big end fitting.

[den]

A more experienced friend had a look today and noticed that the **whole rotor** was slightly eccentric. He suggested that either the rotor was slightly ill fitting on the taper or that the crank was out of alignment after a new big end fitting.

[keleto]

I has a look and inspected and dressed the taper fitting as well as possible and it is a lot better now, although there is still some slight eccentricity. The dwell is fine so I guess the only downside will be accelerated wear on the points heel and spring, and some fractional increase in vibration which I can live with. Maybe in the winter I will get the crank properly checked if I strip the motor.

[Blurredman]

Hi guys, sorry for not coming back to this until now, I've been on holiday in Ukraine (I drove there).


Just today I looked at the points again. I have managed to get the bike to run fairly well but with some issues.

I managed to angle the stator so that the points sit closer to the rotor.
Then I tried again. First I set the gap, then found that the adjustment plate does give me a slight opening before top dead. After doing that the actual gap is probably twice that of what it should be. I may look into it a lot more in a bit but I need to get it MOT'ed to use it for work. I'm on the lookout for an electronic ignition kit which seems to have disapeared on e-bay, though I cannot justify spending the cost on the self exciting system.

The bike runs pretty sweetly enough and has the smoothest rpm needle I have ever seen on an MZ. It stays absolutely dead still at idle. I am not sure whether that is caused by the points being out of whack, but the bike seems to pull through the rpm okay. Like I said though, once it is on the road I can tinker a bit more with it. You can only get so much from going up and down the road outside. You need proper 'average' commute driving.

Thanks for everyone's help. It is much appreciated!

It's an absolute dog of a bike and I always thought the 251's quite ugly but form over factor this particular MZ bike is to me.