Front Cylinder Overheating!!!
Thread Starter
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6th Gear
Joined: Apr 2016
Posts: 11
Likes: 0
From: Ft. Worth, Tx
Front Cylinder Overheating!!!
I've done some upgrades to my 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. 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.
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. 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.
Road Captain
Joined: May 2014
Posts: 648
Likes: 35
From: San Diego
290 engine temp or oil temp? What are you using to measure the temps? I've seen 320 engine temps on my bike and didn't have any paint bubbling on it? Also how long have you been running in this build?
Thread Starter
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6th Gear
Joined: Apr 2016
Posts: 11
Likes: 0
From: Ft. Worth, Tx
290 was the external temp on the head just to the left of the spark plug and above the exhaust. The rear was about 185 in the same areas. I have an infrared thermometer. Paint on the heads was fresh. So, it didn't have time to properly cure through heat cycles before hitting extreme temps.
HDF Community Team
Joined: Jun 2006
Posts: 12,776
Likes: 2,607
From: san antonio
Depending on the conditions under which the temp measurement was made, 290* is really not that hot for head temps. The paint bubbling is probably due to improper curing. Take the bike out for a ride and after say, 50-75 miles, pull over and take temp readings on both cylinders and see what you get. Not time to panic yet............
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Thread Starter
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6th Gear
Joined: Apr 2016
Posts: 11
Likes: 0
From: Ft. Worth, Tx
I was doing the runs to cure the paint per paint specs. I did three 15 minute runs with 20 minutes in between. It was on the 3rd that the temp on the front cylinder began to climb rapidly and I smell and see the paint being scalded. That's when I took the temps. I'm leaning heavily on an intake leak. Either way I've got have the heads stripped and repainted. But, I'm going to reassemble and diagnose the issue before I paint them again. Nothing a little time and effort can't fix. Thanks for the input guys.
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Road Captain
Joined: May 2014
Posts: 648
Likes: 35
From: San Diego
If it's intake leak why not test real quick with brake cleaner or propane at the intake seals? Also any codes or abnormally high idle. I had intake leak causing 1800 idle and it also threw and IAC error.
