Has any documented "normal" exhaust primary temps?

[93Bandit]

For a while now I've suspected my 850 is running lean on cylinder 1 due to exhaust primary pipe color and further confirmed when i noticed an air leak on the cylinder 1 carb to head boot. I will be replacing those boots soon to address this issue and hope that clears up the issue.

This got me thinking though, that if you have an accurate method of measuring each individual exhaust primary coming off the head, you could compare temperatures to identify a problematic cylinder. I have a Fluke laser thermometer gun I used to measure the temps. Please note that I've been having issues with the gun staying powered up (battery contact issue) so my findings may not be accurate. Also, the bike was idling during this test and was as close to operation temp as it can get, idling in the garage on a ~25 degree day.

Anyways, best I can tell with the gun being finicky, cylinders 2-4 measured approximately 250 degrees Fahrenheit on the bend of the exhaust primaries, where they turn down by the frame. Cylinder 1 was reading approximately 100 degrees hotter. Has anyone gotten accurate exhaust temps and recorded them? If so, are my findings anywhere near "normal"? I'm going to see if I can get my fluke to operate properly and do the test again.

[dorkburger]

I've done it as a quick identifier of a problem cylinder and its quite a handy method. For those without an IR thermometer, a squirt of water works too. I seem to think the good cylinders were in the 500° range, but I could be wrong.
Also, be aware that different finishes may give different readings i.e. chrome vs black. The IR thermometers read a larger area the farther it is from what is being measured, so you will need to be pretty close to the pipes. There should be distance vs. Area measured scale on the thermometer. My IR thermometer needs a small folded piece of paper under its 9v battery to maintain contact....

Make sure you replace the O rings when you do the boots.

Edit - depending on your bike's carb boots, O rings may or may not apply. If they bolt to the head, they apply....

[Gorminrider]

^^^good point. It's called "emmisivity". From a Fluke pdf:

"You should be especially wary when measuring the temperature of shiny
metal objects, but even reflections off of glossy paint can affect accuracy. Putting a piece of non-
reflective tape (such as electrical tape) over the shiny surface or applying some flat paint gives you a
target from which you can get a better measurement"

There are tables online too for various surfaces and materials.

[greg78gs750]

also I should point out your test is pretty much useless as it stands, your meter is dodgy and there is very little chance of getting a bike up to operating temp by idling in the garage, it really takes like 25-30 minutes of riding to get there.... I know that wasnt your question, buuut......

[Steve]

I can check mine tonight.

.

[Steve]

OK, I checked. Not what I would call "full operating temperature", but I did run the engine for a couple of minutes at about 3k RPM after warming up enough to remove "choke". Note that this only takes about 20 seconds on my bike.

After running a couple of minutes, holding the meter about 2 inches from the top bend, I read 260°, 210°, 250° and 250°. I guess my #2 could use some adjustment.

Or maybe #2 is correct and the OTHER three need adjustment.

.

[93Bandit]

It only takes your bike 20 seconds to warm up enough to remove choke???? What was the outdoor temp when you did this? Mine takes a few min before it'll idle without choke. And a few more min of idle before it'll run well enough to ride. However, I do have a vac leak and hadn't adjusted the valves yet so it may be better now. Won't know till it warms up enough outside to ride.

Interesting temps though. that's basically what I found aside from cylinder one. Is your bike running well? If so, I'm going to keep my fingers crossed and hope the issue I've been having is isolated to cylinder one and can be fixed with a new boot.

[greg78gs750]

pretty safe bet that steve's bike is running as close to tip-top as it gets.

[93Bandit]

pretty safe bet that steve's bike is running as close to tip-top as it gets.

Exactly what I was thinking. So me thinks that even with my dodgy meter, my readings may not be that far off which is comforting.

[Steve]

It only takes your bike 20 seconds to warm up enough to remove choke???? What was the outdoor temp when you did this?

I think the outside temperature might have been about 30°, but it was in the low 50s in the shop, where it lives.

It doesn't matter much, though, I set the "choke", turn the key ON, give the starter button a stern look and the engine starts.

During the riding season, the sequence is:
- roll the bike outside, close the door
- put on riding jacket
- start bike with above sequence
- put on helmet and gloves
- adjust "choke" because it's now idling a bit high (over 2000)
- get on, start down the driveway
- pull out into street. By the time I'm in third gear, "choke" is completely OFF
- elapsed time is well under two minutes by the time I am a block away from home.

pretty safe bet that steve's bike is running as close to tip-top as it gets.

Yes, it starts and runs well, but I still need to address my little oil "leak" that started last summer. That will involve a base gasket replacement, and I want to get that done WELL before Brown County sneaks up on us.

93Bandit, if you get stumped or just need some final fine-tuning, bring the bike down. I'm only about 3 1/2 hours south of you. Make arrangements ahead of time, we can spend a full day in the shop.

.

[93Bandit]

I think the outside temperature might have been about 30°, but it was in the low 50s in the shop, where it lives.

It doesn't matter much, though, I set the "choke", turn the key ON, give the starter button a stern look and the engine starts.

During the riding season, the sequence is:
- roll the bike outside, close the door
- put on riding jacket
- start bike with above sequence
- put on helmet and gloves
- adjust "choke" because it's now idling a bit high (over 2000)
- get on, start down the driveway
- pull out into street. By the time I'm in third gear, "choke" is completely OFF
- elapsed time is well under two minutes by the time I am a block away from home.




Yes, it starts and runs well, but I still need to address my little oil "leak" that started last summer. That will involve a base gasket replacement, and I want to get that done WELL before Brown County sneaks up on us.

93Bandit, if you get stumped or just need some final fine-tuning, bring the bike down. I'm only about 3 1/2 hours south of you. Make arrangements ahead of time, we can spend a full day in the shop.

.

Interesting sequence. Mine is the same, however I start it immediately after I push it out of the garage. The I shut the door and get ready. I turn the choke off by the time I'm on the road. Maybe I should run it with the choke on slightly, for the first few miles. That may help.

I will definitely take you up on that offer! PM me your address if you don't mind, I'd like to see how far and what route to take. Do you think we could sync the carbs in a day? I decided to fix the vacuum leak and adjust the valves before trying to mess with rebuilding the carbs because they may not need it. But they might need to be synced.

[Steve]

PM coming shortly, but route is easy. I-75 south. When you get through Dayton, turn left.

Carb sync is done in a few minutes. If you ride down, about the only thing that can't be done to a hot engine is a valve clearance check. Everything else is possible, and usually done well within the span of a day.

If you trailer it down , a valve clearance is possible.

.

[93Bandit]

PM coming shortly, but route is easy. I-75 south. When you get through Dayton, turn left.

Carb sync is done in a few minutes. If you ride down, about the only thing that can't be done to a hot engine is a valve clearance check. Everything else is possible, and usually done well within the span of a day.

If you trailer it down , a valve clearance is possible.

.

Awesome! I've already done valve clearances, so all I need to do is replace the carb boots to fix the vacuum leak and then it should be good for a road trip. 👍

[Wingsconsin]

These are the exhaust pipe temps near the head -
Just an exercise on my '83 GS850GL
Might get you the information you desire?

[93Bandit]

Thanks, Wingsconson. Btw, what's your idle speed? It sounds kinda high, or is that normal?