Backfiring when starting

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Feb 18, 2011 | 05:55 PM

Don.M

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Backfiring when starting

I recently purchased a 98 fatboy with 9000 miles. Stock motor, mikuni 42, stock jets, screamin eagle ignition module #32630-96, screamin eagle coil #31647-97, stock cam sensor, and vance & hines pipes long shots or big shots. When trying to start, I pull the choke, and attempt to start. It acts like it wants to but never does. If I give it any throttle, it backfires very loudly and still does not start. It will eventually start if I crank the throttle a lot and ignore the backfiring. When it finally starts and warms up, it runs well. I am trying to test the coil at this time. Does anyone think this may be an electrical or fuel issue? Any suggestions would be greatly appreciated.

Thanks
Don M

Feb 18, 2011 | 08:24 PM

1bd99stc

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From: wisconsin

This could be a couple of problems, 1st I would get it running and check the ignition timing, if that is correct move on to the ignition module, is that a single fire style or a dual fire, verify that the coil corresponds with the module i.e single fire coil with a single fire module. If all checks out then move on to the carb, you say it has stock jets what do you mean by this? The jet numbers on a CV Keihn are not the same on a Mikuni. When you get that far post the jet sizes for us, I am running a similar set up as you so I can tell you what I am running for a carb set up that will get you close depending on elevation.

Feb 18, 2011 | 08:27 PM

Dr.Hess

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From: NW AR

Backfire through the carb or through the exhaust pipes? If the carb, then I'd suggest that your enricher is not working.

Feb 18, 2011 | 08:32 PM

topfuel7

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From: central NC

Sounds like timing is to far advanced.

Feb 18, 2011 | 08:46 PM

1bd99stc

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From: wisconsin

I just looked up the part numbers for the module and coil, the coil that is listed for that is a 31653-97, I'm not sure what the difference is but you may want to also look at that as a possibility.

Feb 18, 2011 | 10:33 PM

orbiker

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From: Springfield, Oregon

How old is the gas and how was the bike running before this started happening?

Feb 18, 2011 | 10:34 PM

Don.M

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Thanks for your suggestions. I checked the numbers on the ignition module and seems to be a recommended part. It is dual fire to the best of my knowledge. The coil seems to be hard to find information on. The jets are needle jet 97 with the clip in the 2nd posistion. The main jet 160 pilot jet 20. The choke cable is a Harley cable with the spring and plunger being Mikuni. The bike is only backfiring thru exhaust pipes. I had the bike running with timing slowed pipes became very hot. I checked the ohms on coil primary was 2.8 and secondary was 19000. I read 2-3 was good on primary and 10-13 for secondary. Don't know much about this. Could it be firing at the wrong time would that be caused by ignition module. I don't know how to test that.
Thanks

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Feb 19, 2011 | 07:22 PM

Don.M

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I took the carb off today and run cleaner thru it all, seems there might have been some junk in the tube that allows the enrichner to draw the fuel up out of the bowl. I have tried starting it several times since and is starting good, I will see tomorrow after it sits all night. I am going to put an ev27 in it so if any one is running a set up like this I would be curious to know what jets you are running.

Thanks for all the help. Don