Today a local, XR650L owner loaned me his XRs Only temperature dipstick. Therefore, I was able to take a ride and compare the oil temperatures between my TTO Temperature Gauge and the oil reservoir.
As you can see in the following photograph, the oil cooler receives an unobstructed airflow over the front wheel, and below the front fender.
The above and below photographs also reveal the oil lines are well protected by the forks and their high location inside the outer edge of the fuel tank.
The motorcycle must warm up a bit before the temperature of the oil in the reservoir stabilizes.
However, after the temperature stabilizes, the oil temperature in the reservoir is 25 degrees cooler than the oil temperature exiting the engine, when the bike is idling. After riding about 50 miles, I took the following photograph of oil temperatures with the engine idling.
As you can see, the TTO temperature probe located in the oil line before the oil cooler shows a temperature of 225 degrees, while the oil dipstick thermometer shows a temperature of 200 degrees.
After the engine is turned off, the temperature of the oil in the external lines and cooler quickly drops 30 degrees in several minutes. In contrast, the oil in the reservoir cannot radiate the heat as well, and the temperature remains elevated. I took the following photograph about 3 minutes after turning off my bike’s engine. The oil temperature in the cooler has dropped to 94 degrees, but the oil in the reservoir is 125 degrees.
If you wait longer before starting the engine, the temperature of the oil in the external lines and oil cooler drops even more. After stopping to take some photographs and enjoy the scenery, I recorded the temperature difference in the following photograph. The temperature at the TTO probe is 97 degrees, while the temperature in the oil reservoir is 160 degrees.
When pushing the bike to it’s maximum oil temperature, the temperate at the TTO probe and the oil reservoir are identical. Indeed, this must be the case. If the temperature of the oil in the reservoir is lower, the reservoir temperature must continue to rise until the two temperatures are equal, or a maximum temperature cannot be reached.
During most of my ride today, the oil temperature at the TTO probe was 10 to 15 degrees hotter than the temperature at the oil dipstick. The temperature difference is greatest at idle and low engine rpms. The temperature difference decreases as the engine load and engine rpms increase; the two temperatures are identical at the maximum oil temperature of the system.
After exited the off ramp from an extended, wide-open-throttle run on the freeway, the oil cooler quickly drops the temperature of the oil it sends to the reservoir. Even after riding about ½ mile, and pausing at several stop lights, the following photograph shows my cooler dropped the temperature of the oil in the reservoir 28 degrees before I parked the bike outside Wal-Mart. The oil coming from the engine is 253 degrees, but the oil inside the reservoir is 225 degrees.
Please note, in this instance, reading the dipstick thermometer alone would be deceiving, since the oil coming from the hot engine is still 253 degrees. It takes a short time for the cooler oil in the reservoir to quench the hotter oil still inside the engine.
I can easily keep oil temperature below 240 degrees if I ride at 65-70 mph on the freeway. When I push the bike continuously, wide-open-throttle for 40 miles or more, I can get a maximum oil temperature of 258 degrees, before the temperatures from both thermometers equalize. Running less than wide-open-throttle will always show the TTO temperature probe running at least 5 degrees hotter than the dipstick thermometer in the oil reservoir.
Spud
