What is a ping ?

Or add another base gasket.

From what you have read now doing some research. Just remember, pre ignition causes detonation / pinging. Detonation doesn't cause pre ignition. But this phenomenon would likely occur when the engine is under a load at wider throttle openings.

Do as "Tinken" says above a thicker base gasket alone could cost very little and if the engine is detonating it would be a negligible expense compared to putting a hole in the piston. If it is in fact detonating its about the same as beating the piston with a hammer.

When I start reading of the left over gasses after the spark and flame front did their thing going off and then different definitions, well I really don't grasp that too well. I would make sure where that stuff is coming from, the text, and see if it is from a similar engine to what you have in mind. Two cycle diesel or four cycle gasoline etc.

Not saying your bike is actually pinging., I certainly don't know.

The flame front/probagation travel in many 2 stroke combustion chambers is such that it is not directed out towards the edges of the piston and its rings. This can be due to the design of the squish band itself just inward of the head gasket sealing area and how much clearance their is at top dead center on the piston. The rest of the dome above that in the heads combustion area many times has a sharp angle like a bowl therefore the flame probagation speed from where it takes place at the spark plug can be directed down at the pistons dome. Not out to the pistons edges, due to the domes configuration in the squish band area. This can be due to the percent rise of the domes on many replacement pistons it self. Or what the pistons crown shape really is.

Relieving the squish band angle,. Making it wider and increasing that angle in relation to the angle of the piston's crown at top dead center and widening it at the same time can be done. Even after cutting or shaving the head gaskets mating surface to increase compression on the head with a considerable increase in compression ratio by as much as a few points, and an increase in compression cranking pressure and at the same time stop detonation issues all together running premium pump gas, all other things being equal.

there is some good info here about pinging, preignition, and detonation but i dont think hes experiencing it..what he has going on is 2-3 seconds after he has let off throttle.

Exactly. I'm out. I don't want to derail anymore.

Thanks guys, I really mean that. I know its hard to say what it is with out hearing it in person. I did not have time tonight to mess with the gas but I just bought some 97 and I will mix it up next.

either i way im sure the 79 wont mind the octane

I'll take a shot. I have heard the sound you describe many times on newer bikes. We call it "lean pop on deceleration". When you "chop" the throttle and coast with the clutch out, the engine is spinning faster than what the carb is metering (throttle is closed). The pilot is the only fuel source, but because the engine is spinning fast and pulling a vacuum, it is pulling too much air for what the pilot can supply fuel.....Lean. We usually put a richer pilot in. You can try the air screw and see if that works. Jeff