setting timing with a turbo

I have a 79ltd, looks like a 78 engine with 1075 kit, so on and so on. It also has an ATP turbo. I was reading a few old forms (Jeff S.) and the ATP instruction say to set your timing retarded. Jeff said to set it 30 degrees or less. Well there is my problem I have a timing light and can find what the service manual says to set it, but how do you know 30 degrees retarded? And that is to right of the mark right?

You need a timing light with an advance dial, or digital, so that you can set the degrees of advance (or inital) that your looking for and the timing light will flash on that degree, so you can tune the timing to it.

I have this one:



$79 i think.

Or you can just retard your timing alot that visually corresponds with around 30, and do it the old way, by turning plate and listening for highest idle, then backing of say 3-4 degrees. take it for a hot ride, and listen carefully for ping/detonation, back off some more if necessary.

Good luck.

So if I get one that only advances (cheap old knob version), I can set to 30 degrees advance have a starting point move back to 0, and change my timing. Right?

They are speaking about full advance here, and not inital advance...

Are you familiar with them both and how the advancer operates?

What is your stock inital advance, and full advance? Mine is 10/40. 10 degrees at idle, and 40 at 3500rpm full advance.

To set full advance lower with these old bikes, you need to set your initial advance lower, unless you plan on modifying the advancer unit.

Simply put, yes you could set your timing gun advance to +30 and rev the bike up to full advance, then adjust so that the light fires exactly on the "T" mark, not the "F" MARK!

My example: "F" mark is 0 degrees to the timing light (exactly when plug fires).
If I add 10 degrees to the gun, the "T" mark now lines up with case mark.
To check full advance I add 30 more degrees (+10 initial) makes 40, and rev the bike till it stops advancing and the "T" mark again lines up fairly perfect with the case mark.

Hope this helps!

If you just rotate the igntion plate to retard the igintion, you are retarding the ignition that amount from idle to full advance. So with a 10/40 ignition advancer, retarding 10 degrees would make the bike very difficult to start and keep running. If you have a 20/40 advancer (typical in the 75-80 900/1000 bikes), you can retard 10 degrees (making it a 10/30 advancer) and still have the bike running at idle.

This is where an ignition like the Dyna 2000 comes into play - the 2000 uses an electronic advance, so any turbo retard settings are only above present rpms - 3000rpm or similar.