Merickk just chimed in on his old post about his 351 failing in Ouray this past summer.

Stuck in ouray - Page 6 - ADVrider

This time it appears there's oil in the coolant. Maybe speculation about the water pump seal, but unknown at this point for sure.

 

I went back and read most of that thread again.

There's an interesting statement there that I had missed earlier.

"You can't run the KLX wide open for long periods of time. It will throw out the oil & cause it to overheat, losing the coolant & causing the sleeve or stock cylinder to crack. The same is true for the 250, 300, 331, 340, or 351."

Really? Stock bike with working cooling system will overheat and self-destruct if you ride it wide open for too long?

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Mikko

 

Certain to? no. Posssible? sure, depending on several factors. Headwind? 200 lb rider? windshield? Saddlebags jutting into the airflow? Maxximum load on a small engine held wide open
It's not the coolant system at first, it's the amount of oil that;s going to get bypassed into the vent system, and forced past the rings under 9,000 rpm under a heavy load. It'll go hours and hours but at some point you;ll see less effciency from the rings, degraded valve seals, over stressed valve seats. Once the critical items start losing their full potential, it begins a re-enforcing cascade. Lower oil lever after having blown a half a cup back into the airbox means the remaining oil is all that is available to do the lubricating, slightly less lubricating capability leads to running a higher temperature, which strains the coolant system to maybe begin to whistle some around on steam pockets, with the results more heat on pressurization be monitored closely for very hot spot. The parts and in particular the materials and the processes used when manufacturing those parts find themselves at the limit, and then small stuff bends metal fatigues crack formation at 10,000 cycles per minute, it makes things like an over stretched poorly oiled cam chain finally breaks, or the tulip on the valve lets go, even just some degradation in the main bearing from cavitation in the oil pump will not take too long to put metal grinding into the oiling system, and then any number of failures my happen.
Try it in your truck. fill the bed with sand, get it down coil bound,now get onto a large dirt oval track and hold ir wide open. Just hold it there. [I]t wiil eventually degrade and the weakest link can be soon identified. Usually within 12 hours.

 

If it takes 12 hours of full throttle abuse to break the engine, I'm not worried.
I often climb long mountain passes pulling a trailer with throttle floored on my truck, and it takes it with a stride.
Would it do that for 12 hours straight? I don't know. Pretty sure it would unless either engine or transmission started to over heat.

I don't quite follow what you say about oil being forced past the rings and oil being pushed into the vent system.

If cooling is working fine and engine temperatures are normal, why would full load operation push oil past the rings or into the vent?
And by such a large amount that the oil pump starts to suck air causing the oil pressure to drop?

Sure, if the oil level is too low and oil pressure drops bad things do start to happen very quickly. But how does riding at "full load" over stress the valve seats and rings if the motor is not being over reved and cooling is working properly?

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Mikko

 

This is my opinion, yours may vary. I have had my KLX for a little over a year now and have been on this site for 11 months. The KLX 250 is a great little bike. It is not very fast, the suspension is fair, the power is very nice. Kawasaki could have made it faster and lighter, but what you see is what you get. Want more power get a pipe, pumper carb, open up the air box, bore it out or do it all[I did ]. It is still not any why near as fast as my KTMs. I know your KLX 250 will tear the orange off my 250 SX and 520 EXC but mine won't. What I'm getting at is give the KLX a brake, the 10,500 red line is a max rpm, it don't mean that a continuous 9,950 will get you very far. Think tick, tick, tick, BOOM. The more you do to it the less ticks you get.

There rag away. Pick one, eh.

I like my KLX and don't mean to offend any one.

 

I do not agree. I do not have to. Oil gets sucked by the rings under HIGH vacuum. Compression can be blown by rings and possibly blow oil into the airbox, but not from running wide open, from wear. Valve seats and seals will do their thing wide open or not no matter for how long. Everything should work fine unless oil or water get low from other reasons.


Take an old V8 car. Put a brick on the accelerator and leave it. It will just sit there and run.

Sure if there is a weak link, you will find it under full load, but running under full load will not just blow the engine in a certain # of hours or minutes. It just does not work that way.

Hot spots and steam? Nope if the coolant is of the proper mixture and full. If the water pump is pumping and the thermostat is working everything should be in harmony.

I beat the crap out of my KLX351 with NO problems in 9,000 miles.

Flame away
David

 

The only waterpump sealing issue I had resulted in coolant in the oil, not the other way around - made sense to me since the coolant is under big pressure. That was a 2-stroke though. Really weird - hope he gets it figured out. Can't imagine the frustration.

People running these things endlessly at redline kinda deserve what they get, IMO.

 

Hmmmm I would never run anything even close to the redline. Nobody can guarantee that.... "I can take a dump in a box and slap a guarantee on it" No thanks, all you guys running close to max....its your funeral.

 

Yeah, I would think coolant in the oil would be more likely on the pump issue. merickk said this morning that the mark in the cylinder is in exactly the same place...interesting. Hayduke's suggestion about something in the bottom end causing this is also interesting, though I can't get my head around that one either. Funny how this thread has gone in a "running at redline" direction. I don't think merickk's problem is really related to that in this case. As I understand it, the best guess for merickk's first failure was a bad press in the liner install. It's hard to believe that the exact same thing would happen in short order again. It kind of makes you consider an already existing problem with his engine, but that's total speculation on my part too.

 

Yup. No one was originally talking about "running at redline", I don't know where that came from. Under full load is another thing.

Digressing to merrick's case. All mass produced engines have tolerances. Some have wider than others, and some are the very end of the bell curve and almost too wide tolerance on some measurement.

What would stress the cylinder in this way would be an engine case where the cylinder deck is machined slightly out of parallel with the crank shaft.
And remember, none of engines are perfectly parallel in that regard.
Some are just very close and some are not...

Just speculation but it is something to keep in mind. All measurements in a mass produced engine are more or less of from the nominal.

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Mikko