Cylinder Head Temperature Gauge Installation

[mr pibbs]

Could you use a gauge labeled trans oil (or anything for that matter) and just hook up a CHT sensor?
I was thinking of something more like this: link

[mousewheels]

Could you use a gauge labeled trans oil (or anything for that matter) and just hook up a CHT sensor?

Sensor technology is different for the VDO gauge in your link. It uses a variable resistance sensor vs thermocouple. Using a thermocouple would not work because resistively, it will look like a 'short' at any temperature. Probably just peg the meter at 400+.
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But your find of the VDO gauge and matching sensor has attractions:

1. Range is covering what you'd probably want to be under.
2. The mating sensor might be small enough to drill/tap the head for.
3. Total cost would be well under a true thermocouple VDO gauge.

BTW - Found a little better price, while looking for a source and data on the sensor for the meter you linked.

http://www.summitracing.com/parts/VDO-310107/ VDO 310107 Transmission temperature gauge $25.99
http://www.summitracing.com/parts/VDO-323086/ VDO Sensor 323086 0-400F, 1/8-27 NPT thread $12.99
Another site shows the sensor characteristics to be "VDO Ohm range sender (10-180 Ohms)"
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Opinion - I'd buy a thermocouple based CHT rather than use this transmission gauge.

[Wheelman-111]

Greetings:

Thanks for thoughtful tips, Mouse! I now believe my thermocouple wasn't the problem.

I grounded the CHT case tonight, just strung a wire under the holder bracket and stuffed the other end under a convenient bolt. The needle "jumps" completely quit. That's good, and bad, as I now believe the 350+ readings are close to true. The scooter hasn't skipped a beat all evening, with 350 showing during WOT for over a minute. Temps climb quickly to approach 400 off-throttle, then take 1-2 minutes to return to 300-325 at idle.

Maybe the stock SA/16 is relatively heat tolerant with its thick cylinder walls and skirts. It's still disturbing that it runs atl least 50 degrees hotter than Flashes I and II.

[scooterwerx]

sounds lean. sometimes knowing is worse!

[Wheelman-111]

Greetings:

I agree it sounds lean, but appears to be running well. 78 stock jet is running with well-oiled stock filter. I even went back and saturated it! Stock pipe, BPR7 plug in deference to Deepinnaharta heat. I can't figure out why it would be lean, and it's easily running up to 45MPH or more with 9:1 gears. I went over everything carefully and even fumed with propane. No sign of an intake leak.

Maybe the extra-tall loads result in higher-than-normal temps. Maybe it's a gauge calibration issue. I plan to try an 82 this evening, although I'm waiting for pipe and bore kit any day now.

[Kenny_McCormic]

350 is fine, it jumps to 400 on decell because the fan isn't running as fast, same reason you run a welder 15 minute after you are done.

[Wheelman-111]

Greetings:

KMcC makes his usual good point. I'm not too worried, because it does seem to run so well and hasn't grenaded yet. Still I kind of wish it ran 300 and jumped to 350 instead. Gauge calibration issue? Let's just keep believing that...

[Bear45-70]

Greetings:

KMcC makes his usual good point. I'm not too worried, because it does seem to run so well and hasn't grenaded yet. Still I kind of wish it ran 300 and jumped to 350 instead. Gauge calibration issue? Let's just keep believing that...

Do you have access to a infared temp gun to check the gauge with. Bets tool I ever bought for chasing heat related issues.

Here's a inexpensive good one.

http://www.harborfreight.com/cpi/ctaf/d ... mber=96451

I have a $30 one from Sears I bought years ago. But I bought the one that reads up to 900┬░ a few years back.

[Wheelman-111]

Greetings:

Great suggestion, Bear. Only where would I point it? Maybe lift the plug cap and aim at the head? I guess not while riding...

[Bear45-70]

Greetings:

Great suggestion, Bear. Only where would I point it? Maybe lift the plug cap and aim at the head? I guess not while riding...

The base of the plug should work fine and the engine does not have to be running. Check it right after you shut it off like you said and compare it to what the gauge says. Then watch the temp climb after shut off and compare that to the gauge.

[Wheelman-111]

Greetings:

I'll try it as soon as somebody buys something.

[mousewheels]

For a quick calibration test, next time you have the plug out, dip that CHT sensor in boiling water.

Better yet, test in the cool of the morning, and re-run the test after Flash III has been out in the deepinnaharta sun. The CHT gauge should have compensation for ambient temperature, testing it cool/hot is a good verification.

[Wheelman-111]

Greetings:

Thanks, Mouse, I'll try those things. Meanwhile I pulled the carb out and re-jetted to an 82 main from the stock 78. Performance difference was negligible, but I believe just a bit better. Temperature diffference was about 25 degrees cooler on average.

It still rose rapidly to 400 or a hair more off-throttle. I'm no longer using the term "jumps" because it seems this is a legitimate value. KMcC appears to have the correct answer when he said the closed throttle/low rpm situation causes the temps to rise. The gauge is surprisingly quick in its response. When the throttle is whacked open at the 400 degree mark, the gauge falls to 325 within 2 seconds. It rarely went below 350 with the smaller jet.

All that seems plausible and consistent with the behavior of a 2-stroke engine and the jetting changes made.

[Wheelman-111]

Greetings:

Suspecting high CHT temps were accurate and the result of very hot Deepinnaharta temps, I pondered my next move. The 82 jet helped but disconcerting trips toward 400 degrees F. acoompanied off-throttle cruising .

What else can I do to richen mixture. Remembering that I had installed Honda-san's new stock filter straight from the package, I wondered if it was intended to be run that way. The Service Manual suggests a saturating dip in GN-2, using a ZipLoc bag to keep hands clean and wringing out the excess.

Out came a Large size and 2 full fl. oz. of the GN-2 oil. I sloshed that thing around in there until it would absorb no more. Then I gave it a good squeeze and got at least an ounce of the oil back. Reinstalled:

Instantly I knew I was richer. A few burbles warming up accelerating from 25 to 30. It lost just a tic on top, although it was still able to muster an indicated 45. But now the CHT stayed resolutely around 300 - it had been more like 350+ before. Off-throttle it climbed only once beyond 350 and came back down to 250 (!) whenever I re-opened the throttle.

So now it's perhaps a tad rich with the 85. Not to worry, Honda-san now has my Uni Pod in the 25.4mm size, ready to ditch the stock airbox and perhaps jet up to 88 if the temps threaten once more.

Oil your filter if you're lean, kids. The bore you save may be your own.

[Towlieee]

the only reason the manual recommends using regular motor oil, is for countries and times when filter oil wasn't available, or was too high priced to constantly be able to afford to regularly clean your air filter.. So if they said you had to use filter oil, people would simply not clean or oil their filters, which in that case, a clean, motor-oiled filter IS better

Your best off running a good quality filter oil, it's tacky, so it drys up and sticks in the filter, and traps dirt better. Leave motor oil on your filter to the third world countries