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Old 02-28-2007, 10:00 AM   #1
Join Date: Nov 2004
Location: Wyoming County, New York
Mileage: ~1200
Primary Sled: 1996 Formula III
Where I sled: Bennington, New York
Posts: 49

What causes backfiring? My 76 Olympique 300 was running great but yesterday after about 30 min. of riding the engine started to backfire under accelleration - it wasn't as bad up on a stand though but it will still backfire and bog. I replaced the plugs and put a new primer line on it and it is also getting gas. Does a mixture that is too lean cause backfiring? A bad coil? Thanks
1970Olympic 335
1972 Elan 294
1973 Skiroule RT340
1976 Jag 3000
1977 Olympic 340
1977 Olympic 400
1988 Stratos 500
1995 Formula SL 500
1996 Formula III 600
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Old 02-28-2007, 11:33 AM   #2
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MXZOOoom's Avatar
Join Date: Dec 2003
Location: Ottawa East
Primary Sled: '94MX470 = Sold '78 spitfire now
Where I sled: Ottawa Caleton, Eastern Ontario and Western Quebec
Posts: 976

Could be a few things!

A bad coil will do it.

First thing though I would check all wires for breaks, or shorting out. Be sure to check the kill switch, or unplug it and then try the engine again.

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Old 03-26-2007, 12:00 PM   #3
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Join Date: Oct 2005
Location: Shakopee, MN
Mileage: 502
Primary Sled: 2001 Yamaha SRX700
Where I sled: Minnesota
Posts: 72

Running lean will do it too. Check your jets to make sure they're clean. Also check the gaskets around the intake of the engine for an air leak.

2001 Yamaha SRX700
2000 Yamaha Phazer
1978 Yamaha Enticer ET250B
1975 Yamaha GPX433G
1978 John Deere Spitfire
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Old 03-29-2007, 10:59 AM   #4
Join Date: Mar 2007
Mileage: 400
Primary Sled: 1998 xcf 440 (485) bored .060
Where I sled: NE michigan
Posts: 41

probably cdi. had the same problem on my 1980 jag 2000
Current sleds:
1998 polaris xcf 440 bored .060... people who did it messed up twice.. but that made it cheaper
1980 jag 2000 (engine upgraded to panther 500cc) (panther gearing installed).. still needs some work though
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Old 04-03-2007, 09:14 AM   #5
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Join Date: Feb 2007
Location: wisconsin Beaver dam
Mileage: 1500++
Primary Sled: 1998 Summit 670 600zl cat
Where I sled: WIS Beaver Dam Or a snow coverd lake
Posts: 1,394
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Try Running the sled after its warmed up and then hit the kill switch then pull the pulls see how they look are they wet or is one to white also see if puld wrires are arcing.
670 SKIdoo
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Old 04-07-2007, 11:31 PM   #6
Shawn Manz
Join Date: Nov 2006
Location: SE Wisconsin
Mileage: 200mi
Primary Sled: 1990 EX570
Where I sled: SE Wisconsin
Posts: 36

I woud check the compression. My two cents. not
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