Exhaust temps????

[BONERACIN]

Does anyone know what is normal exhaust temp? Measured 1 inch down from the head on the pipe with an infrared therometer.  Front pipe is measuring 650 and the rear is around 400. That seems like a big difference.   Compresion test show front 205 and rear 207, cam is a 9b, the spark plugs are the same and the both look good. The bike runs perfect and AFR is good. 48 Mikuni with S&S intake for induction.

Thanks

[BONERACIN]

bump

[1FSTRK]

What rpm are the temps taken at?
Did you confirm AFR at the same RPM?

[BONERACIN]

Temps taken under a no load condition at about 2000 rpms, and the AFR is 13.8. I have a two into one pipe so it is hard to check AFR on just the front.

[1FSTRK]

It is almost impossible to get AFR the same on both cylinders at low rpm with a carb. The cam overlap, egr and uneven motor pulses make it very hard for a carb to control fuel evenly. I went through this with CV carbs,S&S, carbs and mik so it is not the carb but the motor combination. The guys that tune my bike would look for a good compromise between the two cylinders at lower rpm. They all would come up very close when run at mid range and high rpm.

[BONERACIN]

I don't think mine is a tuning issue. The plugs look almost perfect. Is there anything internal that could cause this issue?

[1FSTRK]

Can you test at higher rpm increments to see if they remain the same offset?

[RevFastEddy]

Bone... those are exhaust pipe temps not exhaust gas temps you are reading. I bet the gas temps will be 900 to 1100f at idle and 1800+f under load.  Your pipe temps will increase a little but remember the difference is heat transfer to the metal of the pipe.  FYI it takes about 900f minimum for a plug tip to remain clean so the exhaust temp at idle has to be above that as the gasses exit the cylinder.

[tdkkart]

 With it's uneven timing design, the Harley V-twin is about as close as you can get to having 2 separate motors in one set of cases. The 2 cylinders run completely different, especially with a common carb shared by the 2 cylinders.
Jump over to the EFI related forums and take a look at the Volumetric Efficiency and timing tables that we see on the EFI models. It's not unusual at all to
see 10-20% difference between the front and rear cylinder VE readings, which means there's a 10-20% difference in the fuel they're getting.
Being able to fuel the cylinders individually explains why we can make the EFI motors idle so that they don't even sound like a V-twin, but what's that tell you about the carb'd models??   

Exhaust gas temp is a fun tool to play with, I had great success tuning kart motors almost solely with EGT, but it has it's own set of characteristics that you have to learn. 

[BONERACIN]

I will test tonight at a higher RPM.

[Admiral Akbar]

I will test tonight at a higher RPM.

and under load if you want it to mean anything..

Max

[EGNBLUE]

Does anyone know what is normal exhaust temp? Measured 1 inch down from the head on the pipe with an infrared therometer...

As mentioned above, you're measuring the surface temp of the pipe.

FWIW, little things like pipe material (inside and out including any carbon build up), thickness of the pipe and any coatings, cooling via any air moving across the pipe, and bend location to name a few will have an affect on the readings.

Other things like state of tune, head design, injector/ignition/intake system performance will also cause different readings.

[Templer]

IF SHE AN'T SINGING SHE AN'T CA 14.7:1. GREAT LEG WARMER 

[pwmorris]

You aren't going to learn anything about ex temp till you run it and run it hard (should be over 1,000 degrees)-
Rear is usually going to be cooler unless you are jetted way off. I'm pretty sure you don't shift up in this rare air for a pushrod
v twin but here's an old graph of mine to give you an idea of ex temp.