Flaking piston
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Joined: Dec 2005
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From: poway
We'll have to agree to disagree about that, in a way. I've used an infrared thermometer a good bit. (for cooking mostly). On mine with fairing, lowers and low slung tank, normal easy riding at about 80 degrees and stop. Cylinders frt/rr - 175/275. Heads about 210/225 Let it sit 3 minutes with no breeze and it'll read 225/245 and within 10 degrees on the heads. I've done that check many times.
Chasing an elusive intake leak 2 years ago, I carried a digital thermocouple for several rides. Same conditions as above but pulled the plugs immediately on a stop and put the probe directly on the top of the piston. The front piston would consistently be 80 degrees hotter than the rear. I'm assuming that's because the rear gets so much more oil off the flywheel. As with the cylinders/heads, after 3 minutes the piston temps are near equal.
Obviously the front cylinder/head will be cooler while riding from the air flow, but the actual piston temp is generally higher on the front... from my experiments anyway.
I'm just tickled pink we figured exactly what the #6 switch does
Chasing an elusive intake leak 2 years ago, I carried a digital thermocouple for several rides. Same conditions as above but pulled the plugs immediately on a stop and put the probe directly on the top of the piston. The front piston would consistently be 80 degrees hotter than the rear. I'm assuming that's because the rear gets so much more oil off the flywheel. As with the cylinders/heads, after 3 minutes the piston temps are near equal.
Obviously the front cylinder/head will be cooler while riding from the air flow, but the actual piston temp is generally higher on the front... from my experiments anyway.
I'm just tickled pink we figured exactly what the #6 switch does
Sound like the front cylinder was 100 degrees cooler than the rear.. 175/275. ??
My 113 evo had the front cylinder running about 40 deg hotter than the rear until I backed way off on the ignition timing. Then the rear got a little warmer (20?). You motor actually appears to be running pretty cool to what I've seen. The 113 ran about 300 measuring at the exhaust port left side in front of the plug. Bigger motor, higher compression tho but in a light bike.
I'd be interested in what you used for a thermocouple probe. Most of the stuff I have is simply standard K type twisted wire. What kind of temps were you getting on the piston?
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HDF Community Team
Joined: Dec 2005
Posts: 5,351
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From: NC USA
It was just a $25. chiwanese digital bought off fleabay to set the superheat on my heat pump. K-type, fiber sheathed wire with a bulb on the end. https://www.ebay.com/itm/25484711576...Cclp%3A2334524
That was 2.5 years ago and I honestly cannot remember the piston temps, other than I was surprised at the differential. I want to say in the low 300 range on the rear, but don't quote or hold me to it... been too long. That was on OEM pistons too. Oh, full disclosure, it was a couple months later I finally the problem (that time) was the front wrist pin was stuck in the rod. So the piston was mostly swiveling on the pin, and pin was (mostly) not swiveling in the rod. that may have added some heat to the front piston.
The IR is an old Raytek. I use it often, but mostly during break-in so I can tell when the rings have stopped scrapping so hard on the walls and make sure I'm not over doing things. The wide range between frt/rr I stated are well after break-in and just as I stop, left side of cylinders. It fits in the glove box just under the left handlebar, so it's like within 10- 15 seconds of stopping. The fairing lowers direct a ton of air straight at the front cylinder on mine.
That was 2.5 years ago and I honestly cannot remember the piston temps, other than I was surprised at the differential. I want to say in the low 300 range on the rear, but don't quote or hold me to it... been too long. That was on OEM pistons too. Oh, full disclosure, it was a couple months later I finally the problem (that time) was the front wrist pin was stuck in the rod. So the piston was mostly swiveling on the pin, and pin was (mostly) not swiveling in the rod. that may have added some heat to the front piston.
The IR is an old Raytek. I use it often, but mostly during break-in so I can tell when the rings have stopped scrapping so hard on the walls and make sure I'm not over doing things. The wide range between frt/rr I stated are well after break-in and just as I stop, left side of cylinders. It fits in the glove box just under the left handlebar, so it's like within 10- 15 seconds of stopping. The fairing lowers direct a ton of air straight at the front cylinder on mine.
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