I have 2000, 1200 custom Sportster with 20,000 miles.

The bike start good when cold but "at times" when hot it will roll over and backfire and backfire.

If the engine does not start on the first couple revolutions I found that the best thing to do is to turn the key off and back on, sometimes it will start right away other times it might take a lot of tries. ( Ten ) If you roll the engine over and over it's backfires and won't start. I thought that it might be flooded so I tried with the throttle wide open, no luck, check the spark plugs nice color and dry, tried new plugs.

When you roll the engine over and over, on the last revolution it fires but won't start the engine.

It seem that the timing is advanced, IS THAT POSSIBLE ???


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Sure sounds like timing, have you checked it?

 

My 89' did something like that and it was caused by the jetting. To big of a jet. Not sure if that helps but it would foul out plugs to so if your plugs aren't fouled ever I doubt that's the problem. Not a big mechanic but learning[&:]

 

Mine will do the same thing when hot if I even look funny at the throttle. I try to never even touch the right grip when starting and I don't have the problem.

 

My Evo is the same way, I put my right hand on the Handlebar when I kick it hot, don't even touch the throttle or it immediately floods. Instead of wide open throttle when it's flooded, I tighten the throttle lock/drag so I can crack it 1/4 open, 2 kicks, if no start, open 1/2, 2 or 3 kicks usually does it. Any openning of the throttle will shoot more fuel in from the accel. pump so you don't want to open any more than necessary. I don't touch the thottle at all but let the lock hold it while I kick. Hope this helps.

 

I'm no wrench by a long shot, but, this does soumd like a timeing issue., or possablly an ignition going bad.

 

I would check the crank sensor.By design when they start to go bad it seems as it is worse on a hot engine.If you had a lab scope you could compare the cold signal to the hot signal.Most people don't though.They are not cheap so don't go out and buy one for a one time use.

 

I have had several sportsters and worked on a whole bunch. I have to agree with these guys. It is either flooding the bike or the ignition module is trying to take crap. On any Harley you should be able to pull the choke and hit start with no problems. Also if you have had any jetting done to the carb, i am talking about the stock carb by the way, it should not need the slow jet to be any bigger than a 45. Hope that will help. P.S. while i am thinking about it check your plug wires to for grins, and go ahead and change the plugs.

 

well,your carb ain't carbin,your spark plugs ain't sparkin,and your pistons,well,they ain't workin either.

 

Thank you all for your input. Never thoughtof the crank sensor.