Temp gauge
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Again!
Can anyone who has an older Dtr with the dual speedo/rev-counter clocks tell where their temperature gauge needle lands when at normal running temp?
Mine used to be 10mm from where it lands when you switch off the ignition (5mm into the green) Now it has suddenly shot up to being just below where the red starts! Which seems right
Please tell me where yours is so I can get a good guesstimate if mine is right now...
Cheers now peeps...
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Yeah, I kinda thought green is good, red is dead
but I would like to know the normal operating position, seeing as mine is changed. That worries me 🤨
I should add that the engine is not hot, not blown the coolant out the radiator and generally sweet as feck!... -
@SpookDog Well, I finally spent a bit of time on this, got one of those cheap knock off radiator caps with the temperature sensor in it. Also removed the thermostat and checked its operation.
The thermostat did open on boil, but I trial ran it without.
Both the temperature sensor (Vapor Trail) and the radiator cap now read within what I'd expect (60 degrees centigrade) by removing the thermostat.
That is much more like what I'd expect, so either the thermostat is faulty or they generally run hot. Fine when it was standard, but with it being tuned I do prefer it running at 60. It was previously running at 110 degrees.
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As close to 100c, without boiling, is the sweet spot AFAIK (I seem to remember doing a search) The reason the rad is pressurised is to raise the boiling temp. Same with the coolant rather than straight distilled water...
I think that 60 might be too low... -
@SpookDog Sure, pv=Nrt (Aka Ideal Gas Law). The higher the pressure, the higher the boiling point.
The general consensus for racing two strokes is ~60 mark.
https://www.rzrd500.com/phpBB3/viewtopic.php?t=5029
https://www.thumpertalk.com/forums/topic/437016-2-stroke-recommended-operating-temp/
https://www.cycleforums.com/threads/ideal-coolant-water-temp-for-a-two-stroke-polini.98344/
First few Google searches.
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Sorry been busy with Bad Dog Days...
Makes me wonder why the thermostat opens at just below 100deg though, no?
Are racing thermostats different? (60deg?)
I don’t know, I’m no expert. This is the first 2/ I’ve had that’s watercooled . That’s why I’m so wary of it.. -
@spookdog I am not sold on 100 degrees to be a good riding temperature, as I say, RS operates at 60 with the thermostat. I've been using my DT a fair bit more now, more now than in the last 5 years. And it's now holding a solid 60 degrees once warm. Going to 70 degrees when idling. So I'm happy with that result.
Be interesting to see how it operates in the summer.
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Just found in the Haynes manual that the thermostat should start to open at 63 ~ 67degC and should be fully open (7mm) at 80degC
So you’re right 100degC is too hot. I still wouldn’t run without a thermostat myself, specially on 200 rads’! Have you advanced your ignition much?On a lighter note, don’t listen to me! I’ve managed to blow my head gasket a~fucking~gain!! I don’t have much luck with Athena gaskets
I didn’t catch it early enough to miss out on a partial heat seazure because of my squirrely temp gauge. Also the expansion bottle didn’t overflow like it has before... -
I kno, thing is this barrel & head are different from the ones I had all the troubles with last year...
Even weirder, I’ve topped up the radiator and it hasn’t lost coolant again! I have been keeping the revs low until I can do some exploratory surgery on the top end. I’m wondering if it’s a pinhole in a pipe maybe? Combined heat & pressure/revs
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Can anyone with a multi metre please help me? I need to have someone measure the voltage coming out of the temperature sender wire, to see if it’s 12volts. Just put the red probe to the wire and earth the black...
I only have 3.8 volts and I’m sure it’s not right. Probably a problem with the gauge wiring, but I need to know if it should be 12 volt before I can remedy any faults...
Cheers peeps! -
Yeah, the current passes through the gauge to the temp sender, which is basically a variable resistor that is changed by heat. The hotter it gets the less resistance there is and the temp gauge needle goes up...
It’s ok now anyways. I took apart the Rev counter unit to get at the gauge and found out that there are two resistors in the circuit. So I think the voltage is right. Now all I gotta do is get a thermometer to set up the circuit in a bowl of 80degC water. That should be where it hits red on the gauge according to my thinking 🤪 it means that the thermostat is wide open but the coolant temp isn’t being dumped by the radiator. After that comes meltdown...
I’m hoping I can change the needle position by changing the resistor/s on the gauge to properly reflect temp. At the moment normal running temp is 5mm above the C lowest position. Which is not very helpful... -
Old thread alert! 🤪
Yep, turns out I was running lean as a whippet. 17.5 pilot, 210 main and needle on the 2nd groove. Whereas the correct jetting for my carb is 25 pilot, 240 main and 4th groove from top!...
I live and learn at my own pace it seems
I never thought that jetting could be ‘year of carb’ specific. I thought all tm28mm flatslides were the same ‘body’ and the jetting was different because of the barrel porting in different years/iterations. Never really thought about different, say, powerjet jet sizes which are cast into the body, not a brass screw threaded jet. Or the starter jet? Or air jet? I always tried to jet it to the year of the bike!!
Mind you none of my problems should affect anyone who’s bike is righteous, not a mishmash of bits and blobs! 🥴
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@SpookDog that's interesting. So what you're saying then is though my bike is 240 main jet as standard, if I bought an older carb which had 210 in it I would have to keep the 210 in it? I honestly thought as you did, that the change of jetting was down to porting, exhaust restriction or even different ypvs timing and certainly not different carb internals.
