IainB
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| posted on 11/6/06 at 06:23 PM |
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Backfire through bike carbs
Finally got the engine started today! WOO!!!!
Runs well apart from slight backfiring through the carbs  What exactly causes this? is the ignition too retarded? Idle mixture too lean?
It only happens when you jab the throttle rather than taking the revs up slowly... does this mean its the spark timing?
Iain
http://s43.photobucket.com/albums/e365/IainB1986/
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yorkshire-engines
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| posted on 11/6/06 at 07:08 PM |
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usually caused by an air leak or no air filter put the choke on a little if it goes away too lean due to above
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Danozeman
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| posted on 11/6/06 at 10:29 PM |
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This is interesting i have the same problem.
Dan
Built the purple peril!! Let the modifications begin!!
http://www.eastangliankitcars.co.uk
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IainB
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| posted on 11/6/06 at 10:36 PM |
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Mine seem to be sorted. Checked silicone hose for leakage and turned idle screw 1/2 turn out and its running fine now.
It was only one cylinder that was doing it so it was either a small leak or the idle screw isnt quite ballanced with the others
Iain
http://s43.photobucket.com/albums/e365/IainB1986/
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tks
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| posted on 12/6/06 at 09:09 AM |
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mhhh
when promptyly accelerating,
the spark need to come different (dunno it was earlier or retared)
also more fuel is needed during that small moment...
Sow think it has to do with the spark timeing.
when growing in revs bit by bit you don´t have de squirt and the spark problem.
Tks
The above comments are always meant to be from the above persons perspective.
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TangoMan
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| posted on 12/6/06 at 08:23 PM |
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Fuel
If blipping the throttle produces backfires, it must be fuel. You require less advance with the throttle opne than progressive acceleration as
cylinder filling will be better.
I would suggest that it will be a weak mixture. If only one cylinder I would check that all slides are lifting at the same time and by the same
amount.
As was said previosuly, see what happens with a small amount of choke.
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