Normal cylinder head temperature?

[adamjmc]

I have a 1982 GS850 and was wondering if anybody could give me an idea what a normal range would be for the cylinder head temp. I have one of those infrared wireless temperature gages that makes it really easy to get a reading off each cylinder. If I know the operating temp I could adjust the mixture of each cylinder relatively precisely, I would think.

[Matchless]

I have a 1982 GS850 and was wondering if anybody could give me an idea what a normal range would be for the cylinder head temp. I have one of those infrared wireless temperature gages that makes it really easy to get a reading off each cylinder. If I know the operating temp I could adjust the mixture of each cylinder relatively precisely, I would think.

Very interesting! I actually tried a handheld laser thermometer and measured the exhaust header pipes about 2 inches away from the head and the difference shows up quite easily. I understand that the hotter one will be the leanest, so together with plug chops one should be able to really fine tune your carb idle adjustment in this way.

I have not done it yet and can only say the head temp will probably vary depending on how long and fast you have been riding, and the inner ones may be warmer due to less cooling. Hopefully some experts will chime in here with more meaningfull information.

[hampshirehog]

I'd guess this wouldn't work as numbers 2 and 3 won't be as well cooled as 1 and 4. I think I'd be tempted to tune normally though the temperatures would be interesting.

[adamjmc]

Cyls. 1 and 2 (yes, I meant to say 1 and 2...the ones on the right side) on my bike are running about 100 degrees hotter than 3 and 4. I just rebuilt the carbs and replaced all the o-rings and such. All the carbs were reassembled exactly as they came apart. The bike runs well actually but I thought the fine tuning would help it even more. My guess is that you would want to sync the airflow through the carbs with a mannometer before fine tuning the mixture with the temp gage. Any suggestions?

[Matchless]

Cyls. 1 and 2 (yes, I meant to say 1 and 2...the ones on the right side) on my bike are running about 100 degrees hotter than 3 and 4. I just rebuilt the carbs and replaced all the o-rings and such. All the carbs were reassembled exactly as they came apart. The bike runs well actually but I thought the fine tuning would help it even more. My guess is that you would want to sync the airflow through the carbs with a mannometer before fine tuning the mixture with the temp gage. Any suggestions?

100 degrees seems like a big difference and I would expect 2 & 3 to be the hotter ones, but without anything as a base to compare to I would just be guessing here and that is not usefull. If the bike is running well and your plugs show that it is happy, then you should be OK.

[Steve]

Cyls. 1 and 2 (yes, I meant to say 1 and 2...the ones on the right side) ...

Please, before there is any more confusion, let's get terminology straight.

Cylinders 1&2 are on the LEFT side of the bike.

The sides of the bike are labeled as if you were sitting on the bike, ready to ride.
Therefore, #1 is under your clutch hand, #4 is under your throttle hand.
If you are standing at the front wheel, looking back at the engine, #1 will be on your right, but it's the bike's left.
After all, is it the bike's cylinder or yours?

.

[adamjmc]

Oops...my bad. Let's see if I can get this straight. When sitting on the bike the two cylinders on the left run almost 100 degrees cooler than the two cylinders on the right. That seems pretty extreme to me and I was thinking tuning by temperature would be pretty accurate. Does anybody have a well tuned bike they could get some temp. readings off of? Also, the little screw on the top of the carb body just forward of the cv slide, is that a mixture adjustment? I did some adjusting on it yesterday and it didn't seem to change much of anything temperature or performance wise.

[Matchless]

Thanks Steve for pointing that out, I missed that and read 1 & 4 all the way!


adamjmc,
If you start the bike from cold while idling and you point the laser dot about 2 to 4 inches down each header pipe you will measure a fairly equal reading on all 4 pipes, as they are very similarly exposed to the combustion and cooling air. A small difference may be normal, but large variations (100 degrees!) are telling you something is wrong and usually the much colder pipe is not firing properly or suffering from fuel starvation. Counting the pipes correctly 1 and 2 is then much hotter than 3 and 4. I will immediately assume that the two right hand cylinders are having fuel problems and it is unlikely spark problems as they are on different coils. Pull those spark plugs and see what they tell you.
You most probably know your thermometer, but they usually have a maximum distance for accurate reading. Mine must be 5 inches from the object, so becomes inaccurate if I hold too far away. Yours may have a different focal point.