Safe engine temps?

[User]

I've been searching for a few hours now, and haven't found a solid answer for my question. I figure you guys should know what I need to find out.

I have been tinkering on a 1985 GS 550ES since last fall, and have recently installed a Trail Tech Vapor computer assembly. This little gadget tells me my speed, RPMs, and Engine temp. It has a few other little bells and whistles, but these are the relevant bits. Anyways, after I installed it, I took her for a ride. This is the first time I have had an option to monitor the temp of my scoot. On a very short ride from the house, the temp steadily rose up around 300deg F. I turned around and got her back home as soon as I saw the temp getting above 200deg. I was a mile or better from the house, and when I made it home the temp was right around 300deg. The sensor for the Vapor is a ring that goes around one of the spark plugs. Replaces one of the crush washers, and sends temp reading to computer.

The plugs on this bike are down in a valley, and I can see them collecting heat. I just can't feel good about seeing 300deg reading on anything that relies on oil to lubricate. Am I wrong for thinking this is a damaging temp? What is the normal operating temp for an air-cooled 550? I guess it's actually oil-cooled, but either way I need some insight here. Hope for the best, but ready for the worst I guess.

Thanks in advance.

[Nessism]

Your gauge is reading head temperature, not the oil temp. 300 F doesn't seem hot at all considering your sensor is right on top of the combustion chamber.

[Steve]

"Normal operating temperature" of any engine will depend on where you are doing the measuring.

The only measurements I have seen on any of these engines are those on the 700/750E and 1100E that had an oil temp gauge.
Those numbers tend to hover in the low 200s.

I had an oil temp gauge on my KZ1300, but that was a large, water-cooled engine and tended to run cooler, about 180 or so.

I have no idea what cylinder head temps should be on a good-running air-cooled engine.

.

[User]

I do realize that there is a huge difference between the temp of the head, and the oil temp. However, 300deg just seems dangerous to me? Have I just freaked out for no reason at all? I suppose I should get an oil temp sensor of some kind and monitor from there. Not sure that it is needed, but it's nice to know where your engine is running.

I just figured that somewhere down the line, there was an established temp area for the air-cooled monsters of old. Perhaps I just used the wrong approach? Temp at plugs is very high, and that's okay?

[Krunk_Kracker]

I'd get an infrared thermometer as well. Test different points of the engine while it's running

[User]

^^This crossed my mind. I may go pick one up in the morning if I can get a chance. I'm very curious if I am running hot, or just making a mountain out of a mole hill. Put an amount of work into this scoot, and was hoping to be on the road by now. Hammering out the details.......

[Steve]

If seeing high numbers makes you nervous, then by all means, do NOT install an exhaust gas temperature gauge (pyrometer).

Had one in my turboed Corolla about 35 years ago. After one run of ... let's just say "spirited driving", I saw just over 1800 degrees on the gauge.

"Normal" temps on that gauge depended heavily on how I was running, but cruising at 55 mph (the speed limit at the time), I would see about 800.

.

[GregT]

If you don't know what temps you should see, don't spend money unnecessarily on gauges you don't need...
Provided you are using the correct grade of spark plug, the plug colours will tell you all you need to know.
For a plain bearing motor which I think your 550 is, oil temp is the point to watch - it shouldn't get above 90 deg Centigrade.

[Flyboy]

I would say 300 is quite cool actually, on all of the air cooled aircraft motors I fly on a daily basis, the cylinder head temps sit anywhere between 380 - 420 degrees.
So don't sweat it, your bike is fine.
As Steve says, if big numbers make you nervous, don't install an EGT, you will kak in your pants.

[Nessism]

If you don't know what temps you should see, don't spend money unnecessarily on gauges you don't need...
Provided you are using the correct grade of spark plug, the plug colours will tell you all you need to know.
For a plain bearing motor which I think your 550 is, oil temp is the point to watch - it shouldn't get above 90 deg Centigrade.

Dream on.

[Flyboy]

Ed, I must agree with Greg, again all the air cooled motors we fly, you looking for the oil temps to be around the 200F mark, or about 90C, most of them red line at about 240F or 105C
Ok granted different application and all have an oil cooler, but still.

[GregT]

Dream on.

In one World Superbike motor I built we ran the full synthetic up to 103 deg Celsius which was marginal....and that was water cooled.
I'm referring to plain bearing motors here which I believe is relevant to the original poster.
Roller bearing motors would probably be monitored more accurately by checking internal air temps as oil circulation does not remove as much heat vs a plain bearing motor.

[sharpy]

Anyone suggested on just putting you hand on the cluth/alt cover and seeing if its warm/hot or ouch hot? If you can do that why bother stressing about what a spark plug temp is? I couldnt put my hand on my clutch cover so i installed about a grands worth of cooler and lines. Sucker stays cool and looks trick now

[Flyboy]

Anyone suggested on just putting you hand on the cluth/alt cover

Always, in winter.

[User]

Thanks for the input. I think I just got ahead of myself. This is the first air-cooled street bike that I've ran, and those temps caught me by surprise.