Can anyone enlighten me on how to cure the persistent knocking and pinking sound from my GasGas pro 300 racing. It makes the sound under a bit of throttle load.

I've read about other makes such as jotagas having the same problem and a change of head insert curing it.

Any advice welcomed

Edited March 22, 201511 yr by gasgasshetland

What jetting do you have?

Change the slide from a 3.5 to a 3. You can get a similar result by raising the needle but its difficult to get it to run clean.

Hi, I had the same problem with a 300 Gas Gas which turned out to be a leaking base gasket. It ran very lean at low revs once warmed up. A new [and thicker] base gasket cured the problem. Spraying soapy water around the gasket edge when the bike is running may show a problem.

I take it you have properly cleaned the carb and ruled out air leaks.

The 300's running the Keihin carb do run on the borderline of lean with standard jetting but they shouldn't knock unless really hot or carbond up.

What year is the bike?, Do you have hot weather where you are?

As others have suggested you could change to a #3 slide. You could also try a 48 pilot jet.

If your running at low altitude and not in hot weather then you have a problem some where that needs sorting I guess.

Does this knocking sound mechanical? I ask because my 300 started knocking quite bad the other day i stripped the engine but I can't did any mechanical issue. But my rubber inlet has a crack in it.