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Old 21-09-09, 05:32 PM   #7
Sid Squid
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Join Date: Jul 2003
Location: Skunk Works, Nth London
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Default Re: Why would a (carb'd) bike backfire on starting?

This was written in answer to another related question, and I don't know if your bike was cold or hot or if you'd used the choke or... other things but the principle remains true:

Quote:
Originally Posted by Sid Squid View Post
If you fire up your bike from cold in marginal conditions, it's not unusual to get either a partial, or sometimes a complete misfire, the resulting unburnt fuel rich gas gets shoved into the pipe on the exhaust stroke, next charge goes into the cylinder, fires, and then extremely hot gas gets let into the pipe where aforesaid eminently burnable gas lies waiting to p*ss your neighbours off, voila , big bang in the pipe, enjoy.

Possible causes:

Plugs need a clean/change.
Battery voltage low: Poor quality and duration sparks.
Old or contaminated fuel.
Incorrect choke setting.
It's bloody cold out.
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