backfires after replacing stator and pickup coil - Star Motorcycle Forums: Star Raider, V-Max, V-Star, Road-Star Forum
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post #1 of 22 (permalink) Old 04-26-2014, 08:29 PM Thread Starter
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backfires after replacing stator and pickup coil

Hi
Hoping someone can shedd some light on my issue.
I have a 2009 vstar 650, with about 10k miles. Its been sitting all winter. Tried to start it a couple weeks ago, no spark. I tested the pickup coil which showed dead so i got a new one from ebay.
After replacing the stator and pickup coil this morning, the bike starts, but runs rough and backfires a lot thru the exhaust. Almost acts as if the timing is off.
Could the positioning of the stator affect the timing? Does it have to be installed in a specific position?
Could the carbs be fouled up from sitting all winter? I did put fresh gas in the tank, but i'm thinking the carbs could still have sludge built up.
Would that cause the backfiring? Also, the bike only runs if throttle is applied or if the choke is on, otherwise it will die.
thanks in advance for any suggestions!!
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post #2 of 22 (permalink) Old 04-27-2014, 07:06 AM
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Yes, positioning of the stator controls the ignition timing. When the rotor magnet passes the pickup coil it generates the pulse which, via the electronics, fires the spark. If the pickup coil is incorrectly positioned the spark will fire at the wrong time.
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post #3 of 22 (permalink) Old 04-27-2014, 08:30 AM Thread Starter
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thanks for the reply, that makes sense. But i didn't notice any timing marks or anything like that on the stator. I also checked some of the posts and didn't see anything.
Do you happen to know how the stator needs to be positioned? or point me to a web site that shows that?

thanks!!!
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post #4 of 22 (permalink) Old 04-27-2014, 09:51 AM
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I don't know your bike specifically, since I don't have one like it. I'd be surprised if the stator could be mounted incorrectly unless is possible to fit it into say, three positions with three symmetrically placed mounting screws. It is also possible that different model years used different stators, along with different rotors with the magnets in different locations, but that is only a guess.
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post #5 of 22 (permalink) Old 05-05-2014, 05:05 PM Thread Starter
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i went ahead and took the carbs off and cleaned them, but that didn't help a bit.
I guess my next step is to take the crank cover back off and figure out what the heck could be wrong.
Any suggestions on the positioning of the stator or pickup coil would be great!.
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post #6 of 22 (permalink) Old 06-11-2014, 01:12 PM Thread Starter
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Hello again. I havent had much time to mess with the bike until this past weekend. I swapped the plugs and the coils, back to front, with no luck.
I did notice something i had not noticed before.
When the engine is running, only the front cylinder gets warm, the back one stays cold to the touch. Also, I noticed that the backfiring and flames only come out of the back cylinders exhaust pipe.
If I unplug the back cylinders spark plug wire, the motor runs much better, no more backfiring, although its only running on 1 cylinder.
If i unplug the front plug wire (with the back plug wire plugged in), the motor will not start. This happens with the coils and plugs swapped.
I checked and double checked the cams timing, all marks line up.
Is there something between the stator and the ignition coils that controls the spark timing? could my stator be defective? if so wouldn't it affect both cylinders? i'm at a loss...about to give up and take it to the dealer...any suggestion would be much appreciated.
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post #7 of 22 (permalink) Old 06-11-2014, 01:26 PM
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Since swapping the coils made no difference and it's only the rear cylinder, sounds to me like you could have a valve stuck open.

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post #8 of 22 (permalink) Old 06-11-2014, 01:34 PM Thread Starter
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ouch!!! how can i check that without pulling the head? if i remove the valve adjustment cover and rotate the engine?
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post #9 of 22 (permalink) Old 06-11-2014, 01:38 PM Thread Starter
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also, if a valve is tuck open, wouldn't the piston hit it?
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post #10 of 22 (permalink) Old 06-11-2014, 01:42 PM
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Run a compression check on the motor. No compression (or real low compression) means you have a problem. It's possible that a valve could be stuck partially open and not hit the piston.

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