Fluctuating timing

[advinnie]

Hi all I went to set my timing up today on my 1600 bug but it’s to unstable to read with the strobe gun. The timing is as steady as a rock at idle up to around 2000 rpm, above 2000 rpm the timing starts to wobble a little and the higher you take the rpm the bigger the timing wobble gets. At 3000rpm using the strobe gun the timing is around 25 to 32 degrees BTDC it’s impossible to get it set any better. Has something broken?
What could be causing the timing to fluctuate so much?
Thanks for you help all

[Ol'fogasaurus]

My first reaction is to have the bushings in the dis. checked than (if you have one) check the vacuum advance. You could have a mechanical advance that dances also so it might be best to have the dis. spun on a machine.

Lee

[Bruce.m]

If you can, power the strobe using a separate power source, like another battery. Just to eliminate electrical noise.

Other than that, a loan of a known good dissy would be helpful to confirm, if yours is the problem.

[Phil69]

Depending on how good the ht leads are you could be getting interference. Also the centrifugal advance mechanism may need the springs and weights checking and replacing.

[advinnie]

First off had time to play on the bug today and found out that my vacuum advance unit has stopped working so replaced that and now when it’s fitted I’m seeing 44° BTDC and some where around 25 to 34° BTDC at 3000 rpm. Just off to borrow a different distributor and see if it’s that which is not working

[advinnie]

A known working distributor fitted and now the timing is solid and set to 32°BTDC