Timing drifting

[Seamus murphy]

Bgm stator and flywheel
Strobed the timing to 16 degrees but as soon as start to rev out it drifts to 20.
I've had it set now so it drifts out to 17 to try and stay safe lm doing Adria in two weeks any advice that won't break the bank

[Fast n Furious]

It shouldn't advance like this, but without some complex monitoring gear its difficult to diagnose why. If you can lay your hands on a spare CDI then trial by substitution is recommended.
One thing you can do though is confirm proper voltage from the magneto's ignition coil by using a digital multimeter. This will confirm the condition of the coil which could be breaking down.
Set the meter to 200 or more AC volts.
Remove the green wire from the CDI which goes up to the ignition switch.
Connect one meter lead to the now Free green terminal on the CDI.
Connect the other meter lead to earth.
Start the engine.
You should see at least 60VAC on tickover and around 200VAC when revved up.
Remember to refit the ignition wire when finished.

[ian i.o.w]

Maybe try bgm cdi that's what I have on mine

[MK Monty]

Seamus
I had the same on mine last year it was all over the place so removed my Advance retard as 1st step to rule it out, it went the opposite way on revs. I spent ages messing with pick up heights and ended up with a 1.5-2mm packer under the pickup (something I think is now provided on on the BGM stator), it was better but still not stable. I was using a Maroon BGM CDI as a set and thinking its brand new went back to my original unknown brand stator to finally pinch the CDI from my Special. It was a Ducati one and it was then bang on. or should I say if I set it to 17 it stayed at 17. SO on the basis that a CDI is a dame sight easier to do, go for that first. I ended up with a brand new BGM stator and CDI sitting in my spares box. I fitted it on the special to try and prove it was faulty and it ran OK but did start to simply cut out as if out of fuel. BGM get a lot of good and bad press but I'm not that impressed, and yes I know anyone making parts for a Lambretta has to get passed all us so called experts in the shed with a hand full of spanners. too many variables at the end of the day.

[Seamus murphy]

Mine has a maroon cdi l bought the full set up ie flywheel 12v dc stator Wassell podtronic l was more than happy with the lights etc but this 4 degs advancing has put me off. I will try another 12v cdi and see what happens thanks for th advice those who've replied cheers

[bluebob]

very disappointed with the bgm stator.mine was drifting all over the place.also had to file it to make it fit.adjusted pick up height . so the drifting almost stopped then it packed in after four miles.i also replaced the cdi assuming wrongly that it couldn't be the new stator at fault.replaced with an old indian stator,all fine.i bought anther indian for less than half the price and the replacement bgm is still in the box with its nice stickers.

[Seamus murphy]

Bought and fitted a new ducati cdi it didn't change anything
I've taken the flywheel off. I'm going to try another flywheel with the bgm stator as ld like to keep it because I've wired my scoot for 12v dc..
Any suggestions on flywheel

[bluebob]

seamus.what you describe points to the stator.your flywheel( in theory) should be the best match for your stator.have you check the pick up isn't catching the flywheel.are you confident the pick up height is ok.plus lets assume that you haven't got a twisted crank as this could cause similar symptoms.if you check the above and get no improvement,ther is a guy called Anthony tambs(I think this is the correct name)who specialises in this stuff.maybe he could help you in time for your trip.good luck

[bluebob]

Seamus check out knowledges post on Anthony tambs 12v dc converter.