dhardesthard wrote:
I have been unable to establish a normal because when I see the temperatures climbing past 365 I back off fearing that I may be approaching too high a temperature. That is why I am trying to find someone who can definitely say that an over heating problem occurred at a certain temp just as a ballpark figure. I just don't want to be the one who discovers that limit. I was hoping someone who does dyno runs would be able to suggest a caution range of temperatures.
When I do dyno runs I try to have the motor over 330 degrees before starting the run. It's actually not all that easy to keep the temperature up because the DR650 is so effective at shedding heat.
The Vapor temp gauge only goes up to 399 degrees. If your Vapor is reading 399 you don't know if it's really 399 or 475 or 592. Given that limitation I'd say try not to let it go over 398 for more than a few minutes at a time and you'll be just fine.
Years ago a shop I worked at had an analog cylinder head temperature gauge that we put on an old XL600. You could easily see 500-600 degrees on that bike just riding around normally. Those XL600s did not shed heat well at all. They ran hot and paid the price in engine life. There were a bunch of college students that used their XL600s to commute to the local community college that was about 25 miles from town. The XL600s that did all that freeway commuting would last about 15,000 miles. At that point they would get hard to start and come in to the shop for a 'tune up'. We would do a leak down test, find only about 20% valve sealing and when the motor was torn down we would find valve seats that were no longer round, extremely worn valves and cracked heads. All consistent with too much heat. XL250s used the same way would only go about 8,000 miles.
We don't see or hear about
any heat related problems with the DR650. Even with thousands of them running around without temperature gauges ridden by folks who never even think about the engine temperature.
Most motors will get some discoloration on the underside of the piston from the oil film cooking onto the hot spots. Even mildly run motors will usually have a dark brown area under the center of the piston crown. All the old DR650 pistons I have collected here at ProCycle are still the gray color of bare aluminum on the bottom. Even pistons out of motors that have been personally thrashed on by me. Suzuki made a great design that gets the heat out of the piston and away from the motor.
