Exhaust Temperature

[tsigwing]

My last two takes of gas, I have only gotten about 30 mpg in my 05 RSTD. I have consistently gotten 35-38 as long as I have had the bike. Changed plugs and air filters last year, oil is good, nothing different in the bike or riding styles.

 

Took a laser thermometer to measure the exhaust pipes right where the come out of the cylinders. The front two, which are hard to get a reading on because of the shielding, I think I got ~250. The rears I can see the actual pipe and got ~650 on each. Wondering if I just haven't gotten a good reading on the fronts, or if I am actually having some firing issues. Will pull the plugs and check, but wanted opinions on exhaust pipe temperatures.

[Reddog170]

I do not know about the temps but it sounds like you need to run some sea-foam through it. The other thing that may be an issue, but I am not certain, may be the muffler packing and or air filter. Shaun

[V7Goose]

In my experience you cannot get reliable readings on the exhaust headers with an IR thermometer. Just moving the aim point by 1/4" can produce wild changes in indicated temps, and you have already identified how difficult it is to even access the front headers.

Goose

[Flyinfool]

In my experience you cannot get reliable readings on the exhaust headers with an IR thermometer. Just moving the aim point by 1/4" can produce wild changes in indicated temps, and you have already identified how difficult it is to even access the front headers.

Goose

Not only that but the front pipes have a LOT more cooling air available than the rear pipes, I would expect the fronts to be cooler.

[dingy]

650 seems higher than I have seen on average.

 

Normally I see in area of 450-500F

 

The front and rear would tend to be similar in temp, if taken while bike has idled for a while.

 

As goose said, there is a lot of variance in readings. You have to probe around to find an average, the lows readings are meaningless. The closer you are with an infared, say 12-18", the better & more consistent it will indicate.

 

Gary

[TearlessTom]

You might want to take the reading off of one of the head bolts that is in the same place on each cylinder. That will give you a better idea if one is running way to lean or the difference in temps is too extreme.

 

I agree most temps are much lower than that.

[RSTDdog]

Have you let the bike sit at all or are you riding it regularly? Even sitting 4-6 weeks with E10 and no stabil can potentially cause issues. Bad fuel or blends with higher than the posted E-content can drop mileage.

 

IR thermometer have a spot ratio- They vary between brands. I have a Raytek and the spot ratio is 1:12. IIRC from the instructions at 12" away its reading a 1" diameter area, thus at 6" its only a 1/2 in area at 24" its a 2" area, etc. Need to be sure you are reading the non chrome unsheilded part of each pipe, as mentioned, tough to do on the front.

 

I like to look for lean or dead cylinders starting from cold and using the spit and finger test (Spit keeps you from burning the finger). Live cylinders with pilot jets flowing properly will get hot enough to sizzle the spit usually in a minute or so after cold start up. If after a couple minutes you still have a cold or luke warm one (no sizzle) thats where you need to start looking.

 

RSTDdog

[tsigwing]

Have you let the bike sit at all or are you riding it regularly? Even sitting 4-6 weeks with E10 and no stabil can potentially cause issues. Bad fuel or blends with higher than the posted E-content can drop mileage.

 

IR thermometer have a spot ratio- They vary between brands. I have a Raytek and the spot ratio is 1:12. IIRC from the instructions at 12" away its reading a 1" diameter area, thus at 6" its only a 1/2 in area at 24" its a 2" area, etc. Need to be sure you are reading the non chrome unsheilded part of each pipe, as mentioned, tough to do on the front.

 

I like to look for lean or dead cylinders starting from cold and using the spit and finger test (Spit keeps you from burning the finger). Live cylinders with pilot jets flowing properly will get hot enough to sizzle the spit usually in a minute or so after cold start up. If after a couple minutes you still have a cold or luke warm one (no sizzle) thats where you need to start looking.

 

RSTDdog

 

My bike rarely ever sits for more than a week. It is my primary commuting vehicle, so no it hasn't set. Hope to get a chance this weekend. It is running great, just a surprising drop in mileage. Added some B12 carb cleaner, hopefully if there are any carb issues, this may help.