How hot is too HOT


4 replies to this topic
  • tribalbc

Posted September 03, 2010 - 04:13 PM

#1

I don't mean at what temp you boil over. I would like to know the temperature when you start doing engine damage, warp head, melt piston, etc.
I like to ride really tight nasty stuff, first gear for an hour. In the heat of the summer I really have a problem with it getting hot, no brainer. I have a Boyesen water pump and a 1.6 rad cap which help some. I really need a fan setup, I'm on that soon. I also have a heavy duty skidplate and Unabiker rad guards which compound the problem, but they're needed with the territory.
So I'm thinking of running Evans or something of the like, especially for races when youre not stopping to cool down. But what temp can you safely go to? Will it be much of a difference in temp I feel safe too, or just the assurance I won't lose coolant???
I have a trail tech vector so I see my temps. I'd say it's pretty accurate. Shows me boil around 270 at 1500ft with the 1.6 cap and around 260-265 at 7000ft. I've had the temp as high as 290 at an extreme test at an Enduro in the heat of the summer.....

  • Just_a_trail_rider

Posted September 03, 2010 - 09:00 PM

#2

I love the super technical stuff too. I find that I can keep the coolant so long as I don't ride the clutch. No matter what you put in there, if you ride that clutch, you'll get it real , real hot.

So... gear down a bit and tractor that bike without the clutch.

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  • tribalbc

Posted September 04, 2010 - 05:28 AM

#3

I love the super technical stuff too. I find that I can keep the coolant so long as I don't ride the clutch. No matter what you put in there, if you ride that clutch, you'll get it real , real hot.

So... gear down a bit and tractor that bike without the clutch.


I'm geared down and don't use the clutch that much,it's a speed thing. You need that 8mph every once in a while to cool things down. The big one is when you're stuck on a log or in a mudhole and the wheel is doing lots of revolutions but you're not going anywhere :foul:
I've run as low as 12/50 but now with my engine mods, exhaust, YZ cams and high compression piston I run 13/51. I can walk my bike at idle with no clutch. I still needed to stop over 10 times to cool yesterday on this 100 switchback first gear climb I did, bit of a pain in the :bonk:
I know I need to get that fan hooked up but my real question is.... What temp is going to do engine damage???

  • grayracer513

Posted September 05, 2010 - 07:23 AM

#4

If the coolant boils, it's a problem. Reason being that as the steam bubbles form on the surface of the hot parts (combustion chamber dome and cylinder wall), those parts lose contact with liquid coolant, and the internal metal temperatures spiral out of control. So, boiling is too hot, and needs to be avoided.

High pressure caps can raise the boil temperature several degrees, and fans will help hold the real coolant temps down. If nothing else works, using a high temp coolant like Evans or Zip-Ty is better than boiling. These don't cool any better, but they resist boil over, so the problem of spot boiling can be avoided.

The engine will still be hot, though, and the problem is that the head is generally hotter than the coolant at the upper end of the scale. The main thing is to prevent boil over by whatever means possible. If nothing else can be done, that is, if a fan doesn't address the problem, and you still end up boiling when the whole of the cooling system is healthy, then one of the high dollar race coolants should be tried. The engine will be safer at 350 with the coolant not boiling than at 270 while boiling.

The temperature at which damage occurs is tough to nail down, because the temp you see is not the temperature of the head dome, piston, etc. The real danger occurs when these parts get up around 600-700 degrees, but there's no way to determine when that happens, exactly. The only thing you can really do to ensure safety is to keep the cooling system cooling.

  • tribalbc

Posted September 05, 2010 - 07:58 AM

#5

If the coolant boils, it's a problem. Reason being that as the steam bubbles form on the surface of the hot parts (combustion chamber dome and cylinder wall), those parts lose contact with liquid coolant, and the internal metal temperatures spiral out of control. So, boiling is too hot, and needs to be avoided.

High pressure caps can raise the boil temperature several degrees, and fans will help hold the real coolant temps down. If nothing else works, using a high temp coolant like Evans or Zip-Ty is better than boiling. These don't cool any better, but they resist boil over, so the problem of spot boiling can be avoided.

The engine will still be hot, though, and the problem is that the head is generally hotter than the coolant at the upper end of the scale. The main thing is to prevent boil over by whatever means possible. If nothing else can be done, that is, if a fan doesn't address the problem, and you still end up boiling when the whole of the cooling system is healthy, then one of the high dollar race coolants should be tried. The engine will be safer at 350 with the coolant not boiling than at 270 while boiling.

The temperature at which damage occurs is tough to nail down, because the temp you see is not the temperature of the head dome, piston, etc. The real danger occurs when these parts get up around 600-700 degrees, but there's no way to determine when that happens, exactly. The only thing you can really do to ensure safety is to keep the cooling system cooling.


Thanks so much, that's just the info I was looking for :bonk::worthy::foul:

Hopefully a fan will deal with the issue and if not I know now have another tool in my arsenal....
Once temps are below 70 (happening now) it's not so much of an issue so I would think it shouldn't take too much to tip the scales in my favor.....
And my cooling system is working fine, full throttle MX riding at the track in the heat of the summer doesn't get me above 220.




 
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