2-Stroke engine knock?

[Jfishsolevibe]

Hey guys, long time no talk! Been too busy riding and working! Good and bad I suppose. My 72 Suzuki GT380 has been running great since I rebuilt her carbs (about 2000 miles ago), and now, I have noticed a strange engine knock. It almost sounds like valves kissing, but there are no valves! Haha.

It doesnt seem to effect engine performance, however, when I wind up 1st, 2nd, and 3rd gears, in between each, there is a rapid knock as the pistons do their thing, while the clutch is disengaged. The bike now has nearly 13,000 miles on it, so I was wondering if this could be worn rings and Im getting some slap in there, or if it could be a detonation issue. Im just hoping it isnt the bearings....

Thanks as always for the help!

 

[teazer]

I'd start by pulling the plugs and inspect them under a bright light with a magnifying glass. You are looking for signs of small peppery silver spots or signs of gray all over the plug tip - signs of detonation.

Deto is not usually heard as you roll off between shifts though.

You coul also try the old screwdriver stethoscope trick and see where it's coming from.

 

[crazypj]

You do have the correct haed and base gaskets?
Too thin and the piston could be touching the head
Two strokes fire every revolution, when you chop throttle the pressure is lower so wear in bearings can be heard.
If not piston slap, it could be small or big ends

 

[joevirus563]

I'd start by pulling the plugs and inspect them under a bright light with a magnifying glass. You are looking for signs of small peppery silver spots or signs of gray all over the plug tip - signs of detonation.

Deto is not usually heard as you roll off between shifts though.

You coul also try the old screwdriver stethoscope trick and see where it's coming from.

+1 Plugs are the best way to see of your engine is healthy or not.

Also do a compression test to see if somethings wrong with rings/pistons.