Normal operating temp for air cooled motors?

Hi all,
The thread on overheating got us thinking about this.

Has anyone here used one of those non-contact thermometers to look at head and jug temps on stock motors when fully warmed up? Specifically, compared the temps of bare vs. painted motors?


Good Ridin'
slmjim & Z1BEBE

KZR topic --- Do oil coolers really work? .... see reply & chart by Old Man Rock.

As for painted vs non-painted, I read somewhere that black painted engines run cooler. I think black in general radiates heat better.

Forgive this sidetrack. :kiss:

Years ago, one of the major motorcycle magazines had an article about their test between a black helmet and a white helmet as to which was hotter inside on the rider's head while riding in blazing daytime desert conditions. The test reportedly showed that neither helmet was cooler inside or hotter inside, and that the exterior helmet color made no difference with respect to the heat absorbed into the helmet or reflected away from the helmet.

Good Fortune!

I wonder if paint on an engine would act a bit like insulation and prevent or slow some heat from being shed? If so, the metal of the engine might be hotter than that an unpainted engine even though the outside surface of the paint might be cooler. A gauge that measures oil temperature would show the internal temperature difference, and that might be the opposite of the temperature difference of the outer surfaces. Ed

I've seen instrumented tests before showing engine paint makes little to no difference in internal temperature.

One thing that some don't realize is that a lot of silver engines are painted silver. Raw aluminum is very prone to corrosion and paint helps that situation.

As for engine temperatures, I think measuring oil temp is more useful than surface temperature. On my old GS1000 with an oil temp gauge the temp would get above 300 on warm days when cruising at speed on the highway. Slowing down reduced the temp quite a bit.

I installed a GPz oil pan and oil cooler on my KZ750 during the rebuild. A very simple and clean install since all the parts are factory. Only thing I had to fab up myself was the oil cooler mounting hardware.

I have run VDO oil temp gauges along with thermostatically controlled oil coolers on my two Zs since the 1980's here in the southeast US. Now both bikes have moderately modified motors of small displacement (987 cc, 10.5 to 1 compression), 29 mm Smoothbores, Kerer pipe, one has drop in cams (9mm lift IN, 8.6 mm EX) and the other has stock cams.

The one with the drop in cams ('73 Z1-900) runs a bit hotter as one might expect, at least 10+ degrees hotter. In fact, oil temp on a short trip recently of some 20 miles or so saw oil temp at 220 degrees F while cruising at 70 mph. Now the other bike (with stock cams) might see 205 or so degrees F on the same route on similar hot summer days (95 degrees +). However, oil temps on both bikes will zoom way up from there in stop and go (mostly stop) traffic in these parts. :laugh: In fact, one time the interstate was shut down and my '73 Z1-900's oil temp gauge showed 255 degrees F so I got off the interstate and shut the motor down for awhile.

One idea I've been thinking of to help matters is to install a 4" Derale fan behind each oil cooler along with a 190 degree F thermostat. Such a fan might help control oil temp better in the stop and go (mostly stop) traffic in the summer.

When I switched from AMSOIL 20W-50 MC oil to AMSOIL 10W-40 MC oil, oil temps dropped 10+ degrees F on both bikes.

Just thought I'd share what I've experienced with you all regarding oil temps.

YES!!! Run an oil cooler and an oil temp gauge, because you have to know!

I use this
www.trailtech.net/digital-gauges/tto/surface-mount/temperature
when I raced my GPz, and running the full Belly Pan, I would see temps in the oil pan, where the pickup was, of 280-290 on a90+ temp hot day, and I was running the larger than stock ZR550 Oil Cooler.


I also run this same setup on my daily commuter GPz550, and using the stock oil cooler, I still see temps in the low to mid 200-230* on a hot day. Cooler days, I see 190- low 200*, lane splitting in traffic, and even a little cooler readings when it opens up to let me cruise at 6-7k doing 75-80 mph.

Water heater tanks are painted black. It is said they hold the heat better.
Steve

Matt Black radiates heat away best, makes a significant difference...in the lab.

Most cooling for air cooled motorcycles is from the windblast, radiation and convection losses are minimal.

The factory race GPz750 had an oil cooler mounted in the headlamp apeture IIRC to maximise both cylinder head and oil radiator cooling.