1993 Fatboy Running Rough

[Knuckles]

I will try to explain this the best I can. I was riding the scoot (1993 Fatboy)doing about 65mph, was running fine, then the engine started stumbling as if I was out of fuel, but the tank was full. So I got off the highway, and the bike kept doing the same thing as if I was out of fuel or running on one cylinder, there was also a clunking sound (sounds like a bolt in a tin can)coming from the front cylinder or possibly the carb. I pulled both spark plugs the plugs were dry black and sooty. After the bike sat for a while it started fine and ran fine, after about a minute or two running it would act up again. Also when it acts up which is all the time the carb coughs, I noticed oil on the outside of the carb. After doing some research I replaced plugs, wires and ignition coil. The bike seems to be running a little better but there is still the "clinking" sound seems to be coming from the front cylinder. When the bike was running a blue flame was shooting out of the front cylinders exhaust pipe. Also there did not seem there was the same amount of pressure coming out of both pipes, front seemed less pressure, and felt cooler than the rear cylinder exhaust. If it were a carb issue wouldn't it effect both cylinders? Could it be the ignition module? Or something internal in that cylinder? The bike has 43000 miles.

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[I8SMK4U]

I have dropped a cylinder before but it was the rear and that I heard was a problem for the older Crane CAms Hi-4 ignitions. Blue flame?, check the exhaust brackets. Noise that won't go away, sounds like a good time to do the top end, Heads, valves, cam.

[Gliden]

Intake valve or spring broken?

[Knuckles]

Thanks for the input. Went thru the whole bike and all is tight. Could the timing be off? Iam going to try and look at the valves and all this weekend. I bought the bike about three months ago, this bike is all new to me. Does anyone have a guesstimate of what a dealer would charge to to a top end? Iam also debating on trying to do it myself over the winter.

[1skrewsloose]

You might try a compression test, would tell if you have valve troubles.

[Jim Kraft]

Cam bearing perhaps. I have 21,000 miles on my 99, and I am getting paranoid after reading all the posts on the INA bearing.

[Knuckles]

Thanks for all the input so far, Iam determined to get my scoot back up and running. Trying to squeeze all the riding time I can before this Syracuse NY weather takes a turn for the worse.

Checked the compression on each cylinder. Both cylinders are approx. 140psi. Possibe the timing is off on the bike? Ignition Module? Or Carb?

[Knuckles]

Iam trying to test the ignition module, my manual only tells how to test the module up to 1990, I have a 1993. I am checking the Power supply diode(using the same process as a 1990) connecting the negative lead to module ground black white and the red lead to the postive white wire on the ignition coil, not sure if they are the same, but for a 1990 it states that you should get 800-1300ohms, thats also stating to use th HD multimeter. I am measuring using my fluke and Iam reading .4 to .5 ohms

[Jim Kraft]

Looks like you may have found your problem. I would guess that they are the same, and yours looks to be shorted. Ign. moduals are not cheap, and I would check the coil to make sure that is not the problem, but looks like the modual to me. Still just guessing though. Let us know what you find.

[miacycles]

Check all the involved wiring for the coil issue. The clunking sounds like a valve spring. We just had a bike in the shop with the same symptoms and found a broken exhaust outer spring. Hope this helps. Are you getting the same rain out there that we are getting here ???