Topic: 76' 550k timing question ???

[jimkalfakis]

Hey dudes! I finally got this thing running and running real good after a carb rebuild. I'm using a MAC advanced timing light. It's running smooth at 1000 rpm and I got the strobe light right on the timing marks. How do I check the advance? When I rev it the timing mark goes to the left. If I set the advance on the light to 25* advance and rev it, the timing mark still just goes over to left. What am I looking at? What am I looking for. I'm using the manual but still.

[MoMo]

At idle the light should fire at the 'F' for the respective set of cylinders and when revved the light should fall between the two advance marks.  To clarify a bit-the light illuminates the F mark at the  notch on the crankcase and when revved the light illuminates the two advance marks at the same notch.  My 30 year old Snap On timing light does not have a setting for advance..Larry

[jimkalfakis]

Yes, at idle it's on the F mark. Don't I have to set the advance on the light to approx 26 degrees and rev to 2500 rpms. Shouldn't it still be on the F-mark.

I think I should be a little more specific. I'll check it better tomorrow.

[Popwood]

With revved rpms the advance advances. The light should be the same. My light has no adjustment. with rpms the centrifugal force overcomes the spring tension to allow the tming plate marks to rotate to the right, clockwise.

[jimkalfakis]

so even if I rev it, it should always be on the F mark?

[yo2001]

You got a fancy timing light

You are basically presetting the timing advance on your timing light to 25 deg TDC, so at 2500rpm, you should see the "F" mark lined up. Set the timing light back to "0" and it should advance to the advance mark on the bike at 2500rpm.

[jimkalfakis]

Alright, my timing light is set to 0. At idle of approx. 1000 rpm, the F mark lines up. When I fast idle to 2500-2800 rpms, I have to advance the light to approx 52 degrees.

Without advancing the light, the timing pins when revved to 2500 or more. Are my springs too loose?

[Deltarider]

Your fancy strobe obviously measures degrees for a 4 cylinder. Our engines "count" as a 2 cylinder and since 52 divided by 2 is 26 - which is about the correct advance - you've done well.

[jimkalfakis]

Thanks DELTA! I just needed a little reassurance. The bike runs well but I know I still need a carb sync to finish the motor. I don't have much experience with this old bike.