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Why is it backfiring

2K views 15 replies 4 participants last post by  micoviso 
#1 ·
Good morning, this is going to be long winded sorry but here is my issue I bought an 03 sport 400 from my brother in law cuz he blew the motor up and then he tried to jump start it with a large commercial truck battery he heard a click then saw a puff of smoke come out of the engine start/override/headlight switch then nothing at all, I have a 94 sportsman 400 4×4 with a good motor but bike is rough so I decided to switch out the motors as well as the alternator/charging system so the wires would still be the same on so basically it's now an identical motor to the blown one, everything went great hooked up rad hoses, carb etc but I didn't put air filter and box or clutch back on yet because I wanted t make sure it started first I put a new battery in it so I turned key on hit switch and nothing hence the puff of smoke so I jumped the new solenoid I just put on and it cranked over and eventually fired up but I had to keep throttling it to keep it running but barely running and it backfired super loud out of the exhaust I ordered a new start switch for it, does anyone have any idea what might be causing this? Electrical possibly or fuel related? I am stumped any help would be greatly appreciated thank you
 
#10 ·
Well after much research there's been a new twist to this and yes its all my fault I was misinformed about the year of one of the bikes the one that's getting the motor installed is a 97 sport not an 02 so if I put the original 200 amp stator and flywheel back on it can I upgrade the cdi box on the sport to accommodate that? I would have to figure which wore goes where as there are more and different colored wires on the stator than what originally hooked up to bike
 
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