1987 TT600 - Backfiring -

sarsipious said:

1987 model TT600. Starts easily (now) and idles ok once it is warmed up.
However it backfires under any throttle - mostly when backed off.
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sarsipious.

Welcome to DRN.

First check your valve clearance.

If you have no air leak problem, I would remove the carb and check all the jets. Especially the main jet and holder. Make sure they are properly installed and tight. Also check for a bent slide needle. Take the needle out of the slide and roll it on a flat surface. A bent needle will cause this condition.

Also, check your wiring for a loose connection or bad ground. Remove the sparkplug cap and check for oxidation on the end of the plug wire. Cut about 3/8 of an inch off of the plug wire to expose fresh wire and remove the little resister inside the plug cap and replace it with a piece of copper rod.

Hope some of this helps. :cool:

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sarsipious said:

Seems to falter on every 4th stroke a little.
Trying the air leaks next. I have seen generous amounts of selastic applied to carbie and exhaust joints before. Thinking I might try this approach.
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sarsipious.

If the backfire is mostly on deceleration, it may be an air leak in the pipe. Instead of silastic, make sure the copper o-ring in the head is in good condition and especially the seal between the head pipe and the muffler. If they are bad, replace them with OEM parts. Silastic will burn out.

If the engine falters on every few strokes, you may have a bad (leaky) valve. Might need a valve job.

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