Any ideas why my front cylinder is running about 20-40 degrees hotter then the rear?&nbsp\\; It should be just the opposite.&nbsp\\; This is on a 08 Fat Bob.
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Thanks for any help!

 

rear is probably a little richer.&nbsp\\;

 

Has that machine ever had a custom map made for it at a reputable dyno tuner?

 

Have to ask where you are taking your readings.

 

I'm taking the readings on the cylinder head about an inch from the spark plugs.

 

I was hoping for more specifics and hate to have to do this...

Is perhaps your reading on the front cylinder on the exhaust side of the sparkplug and the reading on the rear cylinder on the intake side of the sparkplug?

 

Glens, at the risk of admitting my ignorance, yes, my measurements were taken to the left of the spark plug on both cylinders.&nbsp\\; Which means it was on the exhaust side on the front cylinder and the intake side of the rear cylinder.&nbsp\\; I'm assuming from your line of questioning that the exhaust side will be hotter.&nbsp\\; Now I have to recheck my readings making sure I'm on the same side (in relation to the exhaust) of each cylinder.&nbsp\\; I'll let you know.

Thanks!&nbsp\\;

 

Try to achieve perfect symmetry with the gun in relation to the cylinders, too.

I like to line the gun up along the cylinder bore axis and get a reading from the base of the sparkplug. The reading will be affected by stuff behind the target spot, if there is any, so take that into consideration.

 

Glens, you were correct!&nbsp\\; If I measure at the correct point on both cylinders the front jug is usually about 10 degrees cooler.
I'm an idiot.
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Thanks!

 

10 degrees is less of a difference than I have seen. Usually at least 30 unless just coming up to temperature. Using Fahrenheit scale.

You should stop by the thread in the Electrical/Ignition/Tuner/ECM/Fuel Injection forum where they are talking about the Nightrider O2 IEDs. They were taking measurements much like you were. I tried to tell them about that and much more. They do not want to hear it...