I have an 89 ZX10 it sat for about 8 months when i fired it up it ran like a pig coughing & spluttering backfiring. I cleaned the carbies put in new plugs checked compressions 170 - 180 on all four. Balanced the carbs to the best of my ability with a two port manometer it runs better but still backfires when i rev it up and there seems to be a ticking noise every now and then through # 1 Carbie

It's usually the carburetor has clogged jets due to gummed gas (esp. Ethanol). One easy thing to try is to adding Sea Foam to the gas tank and run the engine until the mix is pulled into the carb. Then leave it set for a couple of days to allow the gum to dissolve.

If you haven't changed the plugs that would also be suspect, as John said. Also a new air filter.

I would start by pulling and cleaning the carb, air filter and spark plug. Usually the cause starts with dirty air filters that gets the carbs dirty which then cause the polaris to run rich and the plug will start to foul. The unburnt fuel ignites at the wrong time and back fires. A less likely problem would be out of timing.

Greetings ... Malcomb Moar,

I'd be very interested in hearing WHY you attacked your
"carby"... (and were the results real or imagined??).

With any luck it was the same reason and you lost no ground...
Quite the contrary... you can MOVE ON...

I had a car doing the EXACT SAME thing to me...
My temper got the best of me and I kept stuffing my foot into it... until the MUFFLER blew COMPLETELY OPEN....

A decade later a Jaguar XJS V12 did the same wheezing, coughing & back firing... (Ccalifornia catalytic converter)

That I treated more gen6ly... It was also a BLOCKED EXHAUST

Hope this helps


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Did you line up the stator plate line with the notch on the cases? Sounds like your ignition timing is set a bit retarded. I would pull the side cover off and check the timing marks.

Sounds like you covered all the basic's and got sound advice as they the obvious first steps my addition to the above is I think the backfiring is giving a hint towards possible problem here if backfire occurs that generally points directly to lean on fuel now being two stroke I am sure it is getting heaps of fuel but what fuel? I would revisit the fuel mix after a full carbi clean (compressed air through all the jets is crucial here) if you you are mixing 40-1 then ignore this but if you are mixing 30 - 1 ratio or 25 - 1 ratio then definitely consider less oil as a test at least also what petrol are you mixing premium or standard? I would also be testing results with just slight change to the fuel air mix screw backfire suggests it may need to be undone a quarter turn
Oil out the exhaust is very common almost expected from two stroke make sure you try a new spark plug with any change you do and only change one thing at a time then test if no improvement put back the change to original and change something else or you will never know whats going on
To me everything sounds lean on fuel now its just to find a reason it's lean on fuel good luck

The carburator prolly needs to be cleaned out. Try some carb cleaner through the gas tank first.

If I where a gambling man I would almost bet money on there being dirt in the carbies given the age of the machine it is reasonable to assume that there would be some debri at the bottom of the tank. unfortunately there is no magical cure for this your best remedie for the problem you describe is to drain the fuel out of the tank remove the fuel tap & flush the tank clean the fuel tap mesh filter if there is one if not I would be installing an inline filter if one is not allready fitted.Haveing done that remove & thorouhgly clean the carbies this is the only sure way of elliminating dirty fuel or carbies P.S are you sure the fuel you filled up with was not poluted does the servo you purchased it from have a high volume turnover or did you grab that tin of fuel thats been in the garage for the last six months if thats the case it will be stale &this will also give the sympyoms you describe

sounds like ht leads or coils

Either take the carbs off and clean them or add some fuel additive to clean the system. Sounds like you have a clogged jet.