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View Full Version : Rear Cyl Hotter than front - Normal?


motoXcowboy
18th June 2007, 19:38
Just got my bike and have put around 300 miles on it so far, its an 86' 1100, the bike has an oil cooler..and both plugs look normal = tan color.

Rear cyl exhaust pipe (straight pipes) much hotter (4" of blackish blue near exhaust port, thats getting worse). Front pipe only has slight yellow discoloration.

Some guys have told me its perfectly normal..others say I have a problem and will eventually overheat/seize the rear cyl up...

My question is this normal? or is this a sign of a problem. My oil temp gauge has gone over 150 F.

Obviously the rear is going to be hotter due to less air, but still..just wondering if I may have a problem...

What do yall think? Thanks

chrishajer
18th June 2007, 22:40
150 F is no where near hot yet. And I never did figure out which cylinder runs hotter, I have heard theories for either one being hotter. If your bike is running fine and does not have any intake leaks, I think it's fine.

Straight pipes make it hard to jet the carburetor at partial throttle settings, so you might be getting some weird readings from the pipes. Also, there is no front/rear cylinder offset on the stock ignition on the '86, so you can't use the ignition to tune that out either.

So basically, if it's running OK, it doesn't matter which one is running hotter. And 150 F is no where near hot. Maybe the oil temp gauge is defective or you haven't gone on any long rides with it to get the oil temps up.

I say if it's running fine, don't worry about the discoloration on the pipes. That's why stock ones come with heat shields.

--Chris

chrishajer
18th June 2007, 22:40
Oh yeah, your profile says 87 but your message said 86. The 86 1100 heads are some pretty good heads. Keep them :)

--Chris

motoXcowboy
21st June 2007, 00:13
yeah whoops brain fart..its an 87. :doh

I also meant to say its NEVER gone over 150F.

Longest ride so far has been about 1 hour...

yeah it runs fine, except for a bog/sputter if I crack it to 1/2-full open throttle from an idle. I think the carb may be a little dirty seeing as I dont remember it doing that when I bought it. A mechanic friend of mine has an 86' 1100..he said the stock carbs are junk and to upgrade as soon as possible. Said it will get rid of that bog right away..

anyway..thanks for your response.

phantom
21st June 2007, 00:37
Well lets see now ,the front jug is getting all that cooling air while the back jug is not. Well I guess that would mean that the back one would be hotter.Before you buy a new carb how about rejetting first.

ReddTigger
21st June 2007, 00:41
rear cylinders are hotter then the front.. Just a design element.

motoXcowboy
21st June 2007, 00:57
Well lets see now ,the front jug is getting all that cooling air while the back jug is not. Well I guess that would mean that the back one would be hotter.Before you buy a new carb how about rejetting first.


I think the slow jet, accelerating pump, or just the whole carb in general maybe dirty effecting my throttle response...

both plugs are perfect tan color...
rejet? :confused:

phantom
21st June 2007, 01:06
Maybe you need to put a little carb cleaner in gas tank,or spray carb cleaner,Or go buy a spanking brand new carb.Mikuni I hear is the best aftermarket carb.