400EX, do they overheat?
Jul 12, 2001 | 02:20 PM
#12
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Well, it actually goes a bit further than that as well. As the engine gets hot it expands. If it gets hot enough the sleeve, piston, and valves (etc) will start to distort resulting in a loss of compression, thus, leaving you with less power. If they get hot enough they will warp and remain distorted (mainly valves) permanently. I would consider this overheating, I dont know what else you would call it. When the engine gets to hot, its overheated (synonomous). The coolant (and oil in the 400EX) are there simply to draw heat away from the engine its self, when its to hot the engine MAY be to hot. Under pressure you can raise the boiling point of water, I suppose its possible to raise it high enough that it wouldnt boil and still be hot enough to destroy your engine, thus, I dont think overheating should be associated with the coolant its self (in relation to the engine).
Jul 12, 2001 | 04:30 PM
#13
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Honda engines will get real hot ne ways. It is not because you ride so much it is the build of the engine. Hondas are used to being hot. I think the 400ex might have a fan. But i would not worry bout it and go for the 400ex cause you will not have ne problems.
Jul 12, 2001 | 08:38 PM
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madweazl -
Excellent points.
I totally agree, metal expansion is an issue. I guess I was aiming more at the oil point of view. I do think that you'll have oil breakdown before the engine gets hot enough to seriously distort the metal - thus causing damage.
The possible loss of compression is an interesting point. I wouldn't think that under normal operating conditions (no matter how long the engine was running) you would get much compression loss (at reasonable heat level). I guess it matters what the rings are composed of, and how that metal distorts under heat.
Either way, we have two topics here that need distinction:
1. Loss of power over extended operating periods (engine heat).
2. signs/symptoms/possibilities of a free-air overheating.
First, number one. I do know that extended periods of operation does affect jetting/carburetion slightly (see above). I've experienced this time and time again. In fact, its more prevalent with two strokes. After its slightly warmed up (sled, dirtbike, quad, its all the same) - you know, right after it revs clean to the top - that is when you see the most arm pulling power. As the machine completely warms, the hit/pull isn't nearly as strong (relatively). Eventually, the carb will warm along with the engine - that's when you'll see the more boggy, rich-like performance loss.
Now, as far as compression loss along with the above phenomenon - that would also lead to performance loss. That leads to the second point...
2. I don't mean to split hairs, but oil does very little to cool. The gas entering the combustion chamber is the key in cooling the engine (internally). (That's why a lean jetted motor runs hotter, that's also why I suggested that you put a bit larger main jet in your quad - to keep it a little cooler). The oil cooler is put on the quad so that the oil stays cool enough so not to break down.
So what's my point? As long as the oil doesn't break down (using a reasonable weight oil), your rings, cylinder, piston, should be relatively safe. I believe the greatest threat occurs when the oil breaks down - giving rise to metal to metal contact. The only way I can think of metal to metal contact occuring before oil breakdown would be with an improperly tuned engine (overly lean jetting, etc.), or air leaks, or parts failure.
Regarding coolant overflow (i.e., "overheating"
, your point is well taken - technically. Realistically, however, (as I'm sure you know), pressure relief valves, overflow tanks, and coolant boiling points are maintained where they will cause a noticable effect before the engine gets too hot.
Maybe this is all gibberish (laugh).
I do see your point clearly (as much as it seems like I don't!).
I'll give this for you to chew on. 400ex's are noted for breaking down 10w-40 weight oil relatively quickly. That would point the way for ?overheating? (metal to metal contact). Give it 20w-50, it's as happy as can be...
...You know what, this whole dumb point I'm trying to formulate is simply a revolving argument in my head... I'll stop now.
Side note: definition of "overheating" in "The American Heritage Dictionary" - it's not listed, I think we've proved why.
Edit: Ok, my head cleared. I see our misunderstanding. When I think "overheating," I think temporary condition (coolant shoots out - fill 'er up and let cool a while). While you are stating that overheating could lead to a more severe condition, as in engine damage. Yes, by all means a free-air engine could overheat. When a free-air overheats, however, engine damage is likely. BAM! SIMPLE!
ogre
Excellent points.
I totally agree, metal expansion is an issue. I guess I was aiming more at the oil point of view. I do think that you'll have oil breakdown before the engine gets hot enough to seriously distort the metal - thus causing damage.
The possible loss of compression is an interesting point. I wouldn't think that under normal operating conditions (no matter how long the engine was running) you would get much compression loss (at reasonable heat level). I guess it matters what the rings are composed of, and how that metal distorts under heat.
Either way, we have two topics here that need distinction:
1. Loss of power over extended operating periods (engine heat).
2. signs/symptoms/possibilities of a free-air overheating.
First, number one. I do know that extended periods of operation does affect jetting/carburetion slightly (see above). I've experienced this time and time again. In fact, its more prevalent with two strokes. After its slightly warmed up (sled, dirtbike, quad, its all the same) - you know, right after it revs clean to the top - that is when you see the most arm pulling power. As the machine completely warms, the hit/pull isn't nearly as strong (relatively). Eventually, the carb will warm along with the engine - that's when you'll see the more boggy, rich-like performance loss.
Now, as far as compression loss along with the above phenomenon - that would also lead to performance loss. That leads to the second point...
2. I don't mean to split hairs, but oil does very little to cool. The gas entering the combustion chamber is the key in cooling the engine (internally). (That's why a lean jetted motor runs hotter, that's also why I suggested that you put a bit larger main jet in your quad - to keep it a little cooler). The oil cooler is put on the quad so that the oil stays cool enough so not to break down.
So what's my point? As long as the oil doesn't break down (using a reasonable weight oil), your rings, cylinder, piston, should be relatively safe. I believe the greatest threat occurs when the oil breaks down - giving rise to metal to metal contact. The only way I can think of metal to metal contact occuring before oil breakdown would be with an improperly tuned engine (overly lean jetting, etc.), or air leaks, or parts failure.
Regarding coolant overflow (i.e., "overheating"
, your point is well taken - technically. Realistically, however, (as I'm sure you know), pressure relief valves, overflow tanks, and coolant boiling points are maintained where they will cause a noticable effect before the engine gets too hot.Maybe this is all gibberish (laugh).
I do see your point clearly (as much as it seems like I don't!).
I'll give this for you to chew on. 400ex's are noted for breaking down 10w-40 weight oil relatively quickly. That would point the way for ?overheating? (metal to metal contact). Give it 20w-50, it's as happy as can be...
...You know what, this whole dumb point I'm trying to formulate is simply a revolving argument in my head... I'll stop now.
Side note: definition of "overheating" in "The American Heritage Dictionary" - it's not listed, I think we've proved why.
Edit: Ok, my head cleared. I see our misunderstanding. When I think "overheating," I think temporary condition (coolant shoots out - fill 'er up and let cool a while). While you are stating that overheating could lead to a more severe condition, as in engine damage. Yes, by all means a free-air engine could overheat. When a free-air overheats, however, engine damage is likely. BAM! SIMPLE!
ogre
Jul 12, 2001 | 09:13 PM
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Well, I think we've beaten this one up enough and hopefully something was learned by all. Hopefully a thicker oil will do the trick, now I just need to find a bank to rob as they are pretty expensive these days!
Jul 12, 2001 | 10:19 PM
#19
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Any bank will do... just walk in there and say "Give me some money," in a Butthead voice (from Beavis & Butthead). Works like a charm!
Oh, by the way, I owned a '98 mojave before I got my 400ex. Trust me, you'll be all smiles changing to the 400ex. It's a different world.
A year and a half later - bored to a 416, 10.8:1 je piston, webcam (valve springs, hardened rockers), supertrapp pipe, 10,200 rpm rev limiter, uni air filter and elka shocks - let me just say the modifications made as much difference as going from the mojave to the 400ex in the first place (and I'm hard to please). The elka shocks are absolutely unbelievable!
ogre
Oh, by the way, I owned a '98 mojave before I got my 400ex. Trust me, you'll be all smiles changing to the 400ex. It's a different world.
A year and a half later - bored to a 416, 10.8:1 je piston, webcam (valve springs, hardened rockers), supertrapp pipe, 10,200 rpm rev limiter, uni air filter and elka shocks - let me just say the modifications made as much difference as going from the mojave to the 400ex in the first place (and I'm hard to please). The elka shocks are absolutely unbelievable!
ogre
Jul 13, 2001 | 01:01 AM
#20
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I'm pretty excited about getting a new bike. I think I'm riding the Mojave instead of it riding me now, thats when you know its time to get a new quad. Theres tons of stuff I dont know and I'm still a beginner but theres just certain things you can feel right away. I dont care for the suspension, its a little brutal. I here the 400EX has a fairly nice stock suspension. It (the Mojave) has a small wheel track and wheelbase which isnt good for the type of riding I do (no woods and small trails out here). The after market is small too. This is why I'm looking at the 400EX, strong aftermarket and new technology to begin with.