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Old 02-05-2022, 02:10 PM   #1
Jam911
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M900 Misfire

I fired up my M900 this morning...took a bit to start but fired up ok...

..after a few minutes, when warmed up a bit, it misfires / backfires when revved.

...now it had not been run for 8 months and during storage I was advised to coat the inside of the tank with a mixture of petrol and two stroke oil...

...I drained the tank and then filled up with super unleaded before starting...

....would the residual two stroke oil be causing the missfire?

Thanks
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Old 02-05-2022, 04:48 PM   #2
Flip
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It is possible the oil may be giving you a bit of trouble but I would of thought it would blow through relatively quickly as it's so soluble in petrol -did you not flush the tank out before filling it with fresh?

More likely in my opinion though is residue from the old fuel which dried out in the carbs over the time the bike was laid up has gummed up the jets.

These old carburetted bikes were never a fan of long periods of inactivity but that is magnified further as modern fuel has got worse over the years.
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Old 02-05-2022, 06:23 PM   #3
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No in my haste to get it running I forgot to flush the tank...
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Old 02-05-2022, 06:24 PM   #4
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It ticks over perfect but when revved misses and backfires...I hope a quick run will sort it out
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Old 02-05-2022, 07:12 PM   #5
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A little two-stroke in the petrol shouldn't do much harm. If it is that you should be able to smell it in the exhaust. Sloshing the tank about and mixing it up might reduce the effect, but the first thing I would check would be the spark plugs. Changing them is never a bad thing. I give mine 6000 miles and put new ones in. I sometimes notice them going off at slow speed running towards 6000 miles.
You might see some evidence of oil on the old ones or maybe even a wet plug?
An Italian tune up might be the simple answer at the end of the day.
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Old 02-05-2022, 09:04 PM   #6
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Thanks. The plugs have only done a few hundred miles so I would expect them to be ok.

I will try the Italian tune up ...
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Old 03-05-2022, 02:12 AM   #7
Darren69
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It's probably gummed up carbs. I run injector/fuel line cleaner periodically in my fuel. It may help or you may have to clean the jets manually if it doesn't clear itself.
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Old 07-05-2022, 11:17 AM   #8
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So quick Italian tune up and normal service resumed.
Great
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