Loud Popping noises

[Guest]

I ran the bike with loose exhaust pipes for a week (I didn't tighten the bolts down all the way) i know it was stupid of me. Now the bike is making loud popping noises, like gunshots even when i'm on the throttle... it usually only does this when i let off the gas it will back fire a little.. I took off the exhaust pipes to look at the valves and it looks like 3 out of 4 of them are burnt. Can someone with experience tell me whats wrong with my valves? Thank you.

[snapped01]

[ukjules]

Did you run it with the exhausts on correctly ? After ?
Exhausts pipes can for sure make it run too hot ! As can other things...
Was cyl 3 pipe on "better" ?

I would be inclined to check valave clearances , mixture (is it way out ) ( could be way out on just 3 carbs?),
Timing, balance carbs ,plugs , refit pipes properly and see what happens ?

[JTGS850GL]

Can you do a compression check? That will tell you if you have burnt valves or not.

[JayWB]

The part of the valve that you can see in your pictures is not the part of the valve that burns.

The part of the valve that actually seats against the head is the part that you care about, if it burns the valve will no longer seal. Do a compression test, that'll tell you if you have bad valves, pictures tell you very little. As for the color difference between number 3 and the others in your pictures, I'd be looking at carburetors.

[8ball]

After doing a compression test, check valve lash clearance, and if adjustments are needed, do another one to compare the results. also your idle air screws may be out of adjustment. That can cause a bit of popping on decel.

[tkent02]

You didn't mention which bike, I'm guessing a pre 1980 model with VM carburetors?