1981 xs 650 Sharp Hollow noise out the left pipe

[pararescue34]

My bike has been Backfiring/popping like crazy upon decelleration and at idle. I rebuilt the carbs and cleaned them last week because it sat last winter without stabilizer in the tank. It has straight pipes, pods, and i rejetted both the main jet and pilot jets a couple sizes bigger last year.

Rebuilding the carbs didn't seem to help the situation much at all, It still popped and sounded sputtery, just out the left side.

I set the cam chain adjustment and the valve timing (which was way off) and now the bike isn't popping/backfiring at idle, but the left side still sounds hollow and doesn't have it's usual low thump. It runs much more even now, just doesn't sound good.

I richened the mixture screw and there was no change...

What's next? maybe exhaust leak? Thanks for the help!

[grizld1]

You might start by checking float valve function. Level the bike carefully, attach a piece of clear line to the barb on the left side float bowl, open the float bowl drain valve, and set the petcock on "Prime." Fuel should rise in the line no higher than the lower edge of the carb body flange where it overlaps the float bowl. Allow a little room for leveling error.

You didn't mention whether your valves were loose or tight, but if they were tight, you might want to have a leakdown test done; you may have burned one.

I don't know what kind of pipes you're using, but if they're OEM double-wall pipes you may want to inspect for collapse of the inner pipe. This sometimes occurs when the vent in the outer wall becomes blocked and water from condensation or other sources collects between the inner and outer walls and freezes.

[orion61]

Depending which carbs you have your Right throttle cable may be opening the carb at a different rate than the Left so in essence you are having one side doing more work. Look at both when you open the throttle slowly, if the bike starts to rev before the left carb starts to open there is your problem. The bike will still idle fine. Also check your points they may need cleaned.