Scooterotica

Just rebuilt an engine and when checking the timing with a strobe found that the timing was advancing as the revs rose. 18 degrees BTDC became 21 degrees BTDC as I revved the engine. I've had to adjust the stator to get 18 degrees BTDC at higher revs. I haven't got a rev counter so am guessing it gets to 18 degrees about 4000 rpm. Is this normal for an SIL stator?

Yes and you have done the right thing. You should set static timing at around 3000 revs not at tickover (around 1500, but varies). This is around 1/4 to 1/3 throttle.

In reality most of us don't have a rev counter to set timing by so it is just gut feel. My TS1 and GT186 have both been set at 17 degrees using this method without a rev counter.

Thanks very much for the reply. I was pretty sure what I was doing was right, it was the behaviour of the stator that was puzzling me.

Must confess the last two lammies I have timed up had a similar issue where the timing was wandering. On one brand new stator it was fine at tickover but opening up the revs we found the arrow stamped on the flywheel just dissapeared completely. Someone suggested the pick up boxes, even on new stator plate's are sometimes faulty and this was the issue.....

A built in drift of 3 degrees will make setting the static for a variable system a little tricky

i just fitted a new af flywheel and bgm stator. I found that the centre of the pick-up was too low by about 2mm (from memory). I had to use all the supplied shims to get the pick up and magnet perfectly aligned.

It seems likely to me that if the 2 aren't perfectly aligned then as the revs rise the pick up will respond differently. I'd go further and say that if they are perfectly aligned then they will still respond differently, but it wouldn't be apparent until much higher RPM.

I set mine up at tickover then checked it through the rev range after I'd finished and it was rock steady.

Maybe I was just lucky, but it does seem reasonable to me that this would happen.

Have you checked the pick up and magnet alignment?

coaster wrote:A built in drift of 3 degrees will make setting the static for a variable system a little tricky

It's not variable, it's a bog standard SIL stator. It's rock steady at 18 degrees BTDC once it's revving

Have you checked the pick up and magnet alignment?[/quote]
No but like your ignition, it is rock steady once revving