wandering timing

[Monty]

guys. any help appreciated.
Long story but I have problems with my timing moving all over the place.
It all started when I went to fit an M Tech. Now the whole idea is that they advance and retard your timing and this is seen as a good thing.
At the time I had just hold a piston within 500 miles of a rebuild after loosing compression due to stuck rings, turned out I had lost plating on my muggy so it was redone.
Looked at cooling the thing down with the M tech but at the time of fitting I noticed my old stator had 2 lugs broken ( they had been weakened by me opening up the slots so own goal.)
Fitted my spare and went ahead trying the M Tech. After 3 or 4 months I was not happy so removed it. went back to a static 17 DBTDC.
It was a bitch starting and found that I was getting a lot of spit back into the carb rubber, if I removed the rubber it started no problem.
went down the carb route swapping the 22mm for a 26mm Jetex but it was the same. In the end went to check my timing and on a medium revs it was spot on 17 degrees but on tickover it went to 5 to 10 degrees at at that point I got the spitback.
Fitted the old broken stator and the timing was more stable so got a new BGM version 3. Timing still OK on revs but on tickover its wanders now away from 17 degrees back to 25 ish. replaced the CDI with one from a mate and that changes the firing point by 10 degrees but still wanders by around 8 to 10 degrees.
tried 2 different timing lights and they show the same result.
The M Tech is disconnected.
Unfortunately I added the extra wire to use the BGM as DC so Im stuck with it.
Any ideas as to what can make the timing jump around. been thinking about pickup heights but I'm getting big differences by just changing the CDI. at the moment the only connections are the red white and green.
I have a BGM CDI coming but Im running out of ideas
Any comments appreciated

[rosscla]

What flywheel you using?

[Monty]

Standard Indian thats always been on

[jonashford]

I had jumpy timing using a bgm stator, keytronic retard thingy & bgm flywheel, took the flywheel off and it's fine, I've just acquired a bgm CDi to try that but I reckon there's just a conflict of parts somewhere rather than a fault

[corrado]

I think there's an issue with the Ky-tronic and none Ducati CDIs. I'm sure MB have posted that the fault has been rectified on the latest batch but obviously not on earlier batches.

From MB Facebook

The new ones will be coming improved to work with the copy coils which have caused us some small problems.

If your wanting one you can do a notify me on the part and we will get in touch when they arrive.

We've also added some fault finding instructions in the ''TIPs'' section of the product and I've also added it to the instructions.

If your interested please read the links, feel free to ask any questions.

http://www.lambrettaspares.com/spares/s ... u0814.html

http://www.lambrettaspares.com/info/mb- ... s+283.html

[stokky]

I run an Mtech, and having spoken to martin and knowing a few others who run them, the issue with wan ering timing usually comes down to the flywheel needing replacement

[Monty]

As already stated I was disappointed with the M Tech and removed it before I noticed the problem with timing and spitback.
It was the spitback that was the start of the investigation after I went back to Static timing. Thats what I'm after at the moment a timing mark that stays were I left it. Agreed about the CDI and this was again the reasoning for ordering a BGM one. My original one was a Mitsubishi one and has not caused a problem for 4 years. The other was unbranded. I have been shown several Ducati = expensive CDI that look exactly like the unbranded one I have but at £40 i was looking for a bit more than "made in Italy" to multiply the sales price x 50. It did have Ducati on the box but that proves nothing. At least BGM are happy to put there name on it.
My logic is the LT charges the CDI and the pickup should trigger the spark. The big differences between the 2 CDI s tell me its CDI but I'm not sure how the flywheel triggers the pickup. Its normally a hall effect transistor that works when a magnet passes a point. Need to get my head around how this works on a flywheel that is all magnates. Maybe I'm being a bit dumb.

[Lamaddict]

I've had the same problem and fixed it. I was strobing the flywheel and the light mark was bounsing about all over. I replaced the SIL stator with a BGM one and it now works very well, I even put on an Agusto 6000 on and that moves very smoothly. Although, I replaced the whole stator I suspect just swapping a BGM pickup for the SIL would have produced the same result, even just getting a new SIL pickup may have worked.

[Monty]

Its a brand new BGM stator It was the same with an Indian one. The best one I have has 2 broken lugs. 2 diferent CDIs change the timing by 10+ degrees. Still waiting for the new CDI so 1 will strip it again in the morning.

[lambro]

My original one was a Mitsubishi one

Really