Well guys I have a problem with my bike that just started and I haven't had time to tear into it yet but plan on starting this weekend.

The problem is the bike runs like cr#$ for the first few miles then runs fine. In that I mean it is back firing, coughing through the carb, and basically falling on it's face. The back firing is bad sounds like a gun shot and hurts your ears.

It starts fine and idles no problem. I let it idle until the top of the heads are at least warm to the touch. I have not changed anything. I've tried keeping the choke on longer and at different settings but that doesn't seem to have any effect.

I also tried a fresh tank of gas but that didn't help either.

After the first few miles the protesting is over and she runs fine.

Any ideas??

 

Spark plugs are probably fouled from leaving the choke on too long. Try and get the choke completely off, within a minute of starting.

 

Nope, I pulled the plugs and they were fine. Should have mentioned I have had the bike for two years and it has been running fine until now.

 

I suspect it's in your ignition. Water corroded a connection or a connection is loose. Maybe a wire is shorting due to worn insulation or a pinch somewhere that shifts position just enough after the bike warms up to not short anymore. Or perhaps something inside the module or coil is going away.
I hope it's something simple...and cheap to fix.

 

How about water in the float bowl?

 

I wouldnt suspect water because it goes away, then it appears to come back again from what he's saying. Might be a good thing to check though..
I had a problem with my Sportie that I seem to remember being like you describe. I rode it to Daytona, ran great, then all the sudden started acting a fool.. I replaced the intake gaskets and it was good as new.. For the life of me, I cant remember how I diag'd it. The dealer may have told me, but I did the work in the hotel parking lot. You could try carb cleaner from the left side of the bike, spray it lightly on the manifold to head joints and see if the RPM changes, just be careful it doesnt flame up on you..

 

Thanks guys, I'll let you know what I find out this weekend. That is if I get to work on it. We are having a winter storm tonight.

Not sure how bad it will be.

 

Check the timimg plate under the cone. I have seen them come loose

 

84 FXST. Same problem -changed coil - no more problem. When I removed the coil cover, there was some nice black tar in it.

 

could have a bad intake or exhaust gasket.