backfiring????????

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beentryin

beentryin

New Member
Apr 24, 2010
208
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goshen,ohio
today was riding my mb and shut it off with the kill (useing the black wire as a break) and it backfired ,overlooked it and shut it off and did it again.i have ported jug,notched piston port sbp ex chamber. and e3 plug,the plug is running a carmel color,but runs strong
 
corgi1

corgi1

New Member
Aug 13, 2009
2,272
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KCMO
exhaust backfire is un-burnt fuel vapors igniting in the muffler,were u still rolling w/the clutch engaged?,,,and/or did u release the kill button befor the motor quit turning?,,,,,I used to backfire the old van turning off the ignition while going down the street in gear for a short distance and turning it back on while the motor was still being spun by the van being in gear this lit the unburnt fumes in the exhaust system for a most desireable result ,finally blew the muffler apart
 
beentryin

beentryin

New Member
Apr 24, 2010
208
3
0
goshen,ohio
the oil is 50 to 1 lucas synthetic.and the kill button is put inline with the black to act as a break in the line when i flip the switch
 
N

noco

New Member
Sep 9, 2009
343
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fort collins colorado
you backfired it just like corgi1's van(i guess was a standard cause a torque converter wont continue to spin the engine)...you killed your spark but the engine was still spinning pumping air and fuel into your exhaust if your muffler didnt ignite it the engine's flame front did once it excaped through the exhaust port...remember 2 strokes will send some flame out its exhaust port thats why unmuffled dirt bikes still run spark arresters....have fun, dont blow your muffler apart
 
Venice Motor Bikes

Venice Motor Bikes

Custom Builder / Dealer/Los Angeles
Mar 20, 2008
7,272
1,810
113
Los Angeles, CA.
Get rid of that kill switch & just use the clutch to stop the engine. (or re-wire the switch to be between the blue & black CDI wires)
What's probably happening is because you're suddenly disconnecting the CDI's ground wire, you're causing the CDI box to 'fart' & send it's stored up energy (& the power that's still coming in from the mag-coil) wherever it can... which would be the spark plug.
 
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Jumpa

Jumpa

New Member
Aug 12, 2011
607
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Cape Cod
corgi1 said:
exhaust backfire is un-burnt fuel vapors igniting in the muffler,were u still rolling w/the clutch engaged?,,,and/or did u release the kill button befor the motor quit turning?,,,,,I used to backfire the old van turning off the ignition while going down the street in gear for a short distance and turning it back on while the motor was still being spun by the van being in gear this lit the unburnt fumes in the exhaust system for a most desireable result ,finally blew the muffler apart
Click to expand...
My brother and I use to be able to do that in our old ford at will boy did we have some fun going by a police officer , cut the ignition then floor it then turn the key back on and BABOOOOOM cop jumped about 4 feet in the air and grabbed a hold of his firearm like Barney Fife till he figured out what happened he put his hand on his chest jokingly.
I know this post is 3 years old but I figure some one else may have the same issue and get an answer out of it so.. here goes..!
Anyway back to your problem ...make sure the prime valve isnt stuck open thats what happened to my bike that caused my back firing that and the choke was loose and kept falling UP!! or down depending what end your looking at I guess
laff
 
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