What temp should a dtr125 run at
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@declan Bear in mind, by the time the temperature at the coolant cap reaches X, it's already too late.
Personally, I'd run the temperature underneath the spark plug using a thermal coupling, or failing that at the cylinder head.
If your engine is bog standard, then you haven't got to worry, but once you start modifying, temperature is key to understanding the risks of detonation.
So getting as accurate reading as possible is going to help.
The hotter the engine, the more at risk you are to detonation. My DT runs savagely hot in traffic at idle even reaching temperatures of 110 degrees celcius.
But you must appreciate the forumula
pV = nrtThe specific latent heat of a substance is increased as pressure increases. So whilst water may boil at 100 degrees at sea level, that's not the case at 1.3 bar, which the radiator cap is rated to.
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@declan As I say, pressure needs to exceed 1.3 bar, which is massive. If you imagine my car only generates 0.8 bar of boost pressure.
This is a why waterless coolant has its benefits. 1.3 bar of pressure is exerted on the entirety of your coolant system. It's going to be mainly the radiator that will take the most damage. The drawback is that the specific heat capacity of it is less, resulting in higher operating temperatures.
Always Originate, Never Pirate!
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@declan You're not overheating as long as your engine and coolant system still run efficiently. Keep in mind when water is pressurised it requires more energy for it to boil, which is why if you're riding hard on a bike your thermometer might say 105 celcius, but actually it's fine because it is pressurised and therefore your boiling point is raised.
And besides you will feel it if your engine is struggling, it will smell hot, you'll lose power, you'll hear it struggle at lower rpms etc
Yamaha DT125R Blue 2002, XT 125 1982, Yamaha WR250Z 1992, BMW GS650F 1994, Benelli BN302 2015
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Normal, what is normal? Outside temps vary by 20c theese days where im located. You'll have a hard time to reach 70c at the cap in the morning just cruising around, and having a hard time not to exceed 110c at the head in the afternoon on a tight track. Some valid points to where you meassure, temps will read higher in the head, compared to on top of the radiator.
Waterless coolant boils at higher temps, but something like Evans actually remove less heat from the engine, so...whats the point of that? I've never heard of anyone damaging a radiater due to cooling preassure. 1,3 bar isnt normal running pressure, but maximum pressure, before the cap lifts and "bleeds of" the excess. If you're worried, buy a cap with less pressure.
Unless it boils, its fine. Bike is designed to function with 100c or more coolant, otherwise it wouldnt have a 1,3bar cap on. Everyday use should be less of that, ofcourse. But the thermostat isnt even fully open at 80C, come on people...
Unless something is off, its also just about impossible to get detonation in our bikes with super low compression. I've ridden mine on 20% diesel as part of a bet, no issues.
Theres always small exeptions for modified engines, which generate more power and heat, but that goes for any engine.
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Btw, isnt our stock cap a 1,1? Thats what I recall anyway.
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@jens-eskildsen 1.3 on my Starlet, I've been away from my DT so long I can't even remember.
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Found one on ebay that said 1,1 and listed as beeing for a dt125r
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@jens-eskildsen yeah I don’t get Evans because people say it’s safe because you don’t overheat well yes you do it’s just the coolant doesent boil until such a high temp id much rather it boil over as then I know something is wrong rather that having a full rad but a melted piston
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@declan It's not about overheating. It's about the pressure not building up in your coolant system. It's a trade off at the end of the day. And since it's not water, it doesn't oxidise and rot your engine. Our engines are Aluminium, but on a car with a steel block it makes more sense.
You need to take into all the factors into account.
For something you are going to use once in a blue moon, it makes sense since you don't need to drain the coolant system for periods of storage.
Always Originate, Never Pirate!
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With radiator cap sensor my DT runs lowest 60 degrees and highest 80 degrees, whatever the weather. Thats with the stat removed and a shitty dented up radiator, when my headgasket went I had it to 110+ degrees about 4 times just from the steam from the engine boiling under pressure, so im guessing it was alot hotter, never got tight luckily.
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@glynn123 The thermostat provides several features. And the one you're referring to is the less significant one.
Yes the thermostat allows for quicker warming up of the engine, prevention of a heat seizure when the radiator dissipates too much heat, but that is only part of the story.
The thermostat also acts as an intentional resistor in the water jacket. It will prevent stale, localised boiling, of coolant within the jacket, by pressursing the water. Thus the exchange of coolant is made causing any boiled pockets of gas to be moved on and either vented out through the radiator cap, or through the rest of the cooling system.
This feature stops the cylinder distorting, or more importantly, the cylinder head, where most the heat will occur.
