Rubbermount_EFI Cylinder temps - Why big difference?

[XL Dane]

Hi guys, I hope you can help. I took thermografic pictures of the engine and for some reason the front cylinder gets significantly hotter than the rear. About 30deg C at idle.
I have installed a Hammer 1275 kit a few years ago and of course done the timing correction etc. The engine runs fine, and when I did a compression test, the numbers are very close between front and rear cyl.

If timing, fuel and compression is the same for both cylinders, then why is there this big difference in temperature?

At one time I had the cams out, and I suspect that the rear exhaust cam could be one tooth off, but I actually doubt it, but like to be sure.

Is there any way to check that without looking at the cams again? I think I read a post from Aaron/Hammer some time ago how to go about that, but maybe I remember wrong.

In any case I hope you can help.

[juzyHD]

Maybe intake manifold leak?

[MODO SIKLER]

Plugged exhaust for one cylinder? ...due to rats or some other nesting critter? Happens commonly in certain areas.

[shanneba]

Check for exhaust leaks at the head and at the O2 sensors.

A leak that allows outside air to the O2 sensor would have the ECU believe the mixture was lean, causing it to richen the mixture. (I would suspect a possible leak in the rear exhaust)

Do you have a PowerVision tuner?
If you do you can log the O2 sensor voltages front and rear.
You can also log the Rear cylinder head temp to see how it compares to your thermographic pictures.

[sungod]

Originally Posted by shanneba

Check for exhaust leaks at the head and at the O2 sensors.

A leak that allows outside air to the O2 sensor would have the ECU believe the mixture was lean, causing it to richen the mixture. (I would suspect a possible leak in the rear exhaust)

Do you have a PowerVision tuner?
If you do you can log the O2 sensor voltages front and rear.
You can also log the Rear cylinder head temp to see how it compares to your thermographic pictures.

How do your plugs compare?

[rejeanprimeau]

Front exhaust, heat travel back, been knowed since VTwin are born.

[bustert]

you think yours is bad?? shoot a carb machine.
there are many players with the hd engine especially so at idle.
the injected machines fair better but still are effected, notice they are smoother and quiter at idle.
look at the way it is fueled. front intake opens, inrush of air which mixes with the injector mist, carbs are mixing as it goes through the venturi, valve shuts, abrupt flow stop causes a reverse wave. the rear intake opens and the reverse wave mixes in with the inrush from the throttle body.
there is a distortion there and it has an effect on mixture, more so with carbs.
then factor in the 45* separation angle.
then factor in cylinder position in relation to ambient environment.
not unusual for the rear to run diff temp and sound.

forget the one tooth off, if it is, your machine will run like a pig and not like a scalded dog!

[sungod]

Is the bike upright or on the stand at idle? Just wondering if the angle has any
impact on cylinder temp.

[bustert]

hummmm????
like the sun rising and the sun setting???
toilet swirl right or left???

[MODO SIKLER]

Originally Posted by bustert

hummmm????
like the sun rising and the sun setting???
toilet swirl right or left???

... red bull buzz ...