I've done some upgrades to my '99 FXDS TC88 and now I'm having a major issue. The front cylinder is getting super hot. It actually bubbled the high temp engine paint. Temp reached about 290 degrees.

For upgrades I had the cylinder bored to accommodate Screamin' Eagle 1550 pistons. Screamin' Eagle 203 cams. Screamin' Eagle ignition module, coil, wires, and spark plugs. No head work has been done. Valve springs meet factory tension specs. I still have the stock CV carb. However, I did re-jet it for a 95" motor. Vance & Hines Big Radius pipes and Forcewinder heavy breather. I just tore it down last night to verify that I'm getting oil and that the cams were in time. Sure enough, plenty of oil in the top end, and as I figured the cam timing marks were all in line.

I figured it was in time. The bike ran beautifully at idle and a few mid throttle pulls.

The only thing I can think of is the front cylinder is running super lean. The front spark plug is clean and still white. The rear plug looks like it's supposed to, a golden brown.

I'm thinking about putting it all back together and running a compression test to see if I have some sort of an air leak on the front cylinder. If that comes up good I'm not sure what to do next.

 

First thing would be to tear it all down and inspect the damage caused by not having good oil flow.

 

Everything has been inspected. Oil flow is definitely not an issue. There was plenty of oil in the top end.

 

OP stated he had good oil flow. Check for intake leaks first, OP.

 

Oil keeps everything cool.

High temps = oil or fuel issue. Since it is a carbed bike, that rules out the need for a proper tune like it would on an injected bike.

At the end of the day, it needs to be torn down to repair what was not done correctly the first time around.

 

That ^

 

Agree with the others on an intake leak.

 

Only other factor here, if no vacuum leaks, is the bore/piston fit is wrong, and too tight. need to measure piston skirt, and bore to determine, but its a possibility. Having a vacuum leak on one cylinder that is causing that much heat, would cause a run issue, I would think. You report a seemingly decent idle. I have questions about that. But try first. Spraying with carb cleaner should expose that big of a leak. A compression test will not reveal any vacuum/intake leaks. You can run the comp test without having to reinstall everything. just make sure the valves can open and close, is all thats necessary. You don't run the test with a running engine. just remove both plugs, and when cranking the compression should hit 6 times, and thats it. read the results

 

I am afraid, that you may be correct here. something other than a vacuum leak I suspect. I really hope you and I are wrong

 

Might be a plugged up front cylinder oil cooling jet. With no oil spraying on the underside on the piston the front cylinder is going to get hot.