Actually I am talking the same thing. When I say blown up I am including worn out. We had one kid who had probably 50,000 miles on an XR250R flogging it around the woods all seasons. He wasn't easy on equipment by any means. The examples of racing were to emphasize the durability of the KLX design. From a mechanical point of view the smaller engine usually can last longer. Lighter parts carry less momentum making for lighter wear with similar materials in comparison to larger ones. From the reciprocating mass of the piston to the piston rock in the cylinder, smaller/lighter should wear less.

You may not be old enough to remember, but when the Hondas and Toyotas hit the U.S. the comments were similar. "Those small engines won't last." I guess when they started outlasting the old tech poor qualitycars the American manufacturers were pumping out there by 2:1, getting over 150,000 miles when a Chevy was struggling to do 80,000 the point came through - small engines do not necessarily mean high wear. Heck, my wife's Civic has a 1500cc turbo engine in it, probably do a couple hundred thousand in the long run. Our old Mazda 626 had a 2000cc engine which was still running strong at 275,000, problem with it was things like the pulleys suspension and other bits were wearing out and it was not worth the constant replacement of bits. I didn't hesitate when we learned the Civic was only 1500cc, If Honda thinks it will work fine odds are it will, based on their history.

I have never seen anyone put an oil cooler on a KLX250, it isn't necessary. In fact some of the discussion in some threads gets into some engines running too cool. Engines are designed to run within a temperature range and running too cool can wear parts fast.

In regards to temperature control, some of us run a Thermobob, which allows a bypass on the coolant flow while the thermostat is closed. It seems the coolant only relies on thermo-syphen in stock form (hot water rises), so there is a significant difference in temperature from the base of the cylinder to the head. The Thermobob uses a small bypass that allows flow of coolant to get a more uniform and better level of coolant temperature around the cylinder/head at lower temperatures.. Once the thermostat opens the Thermobob system is no longer much of an effect. In cooler weather it could become a factor. I used to have to block off one of the two radiators on my KLX650 to maintain operating temperature (judged by radiator heat - touching the tank) to keep some circulation through the radiators. They would be cold, the engine running at the low end of efficiency. Blocking one got the thermostat open and heating up for better running. On my old air cooled Honda MB5 50cc play bike during the winter I had to actually shroud the cylinder to keep enough heat in the engine. Otherwise it would get so cold I'd have to open the choke to keep it running. Believe me with 50cc you know when it isn't running right.

When you consider the KX250F runs about a quart of oil, has no radiator fan, and no oil cooler that should give a hint. The KLX with near 2 quarts is in little danger of overheating, oil or coolant. Plus if the oil is too cold that can be another issue it is possible to have cavitation in the pump - oil cannot fill the pump, pump spins an air pocket and oil flow issues happen... look it up.

I guess what it is really about (to me) is the facts about the engine, cooling system, and sensors and what it should be to verify if the cooling system is set up right.. The next question is can it be trusted. The information is needed before deciding to make a thought out decision, regardless of which it is. You need to know what the limits are, when the fan and temperature light switches on and off.If the factory set up isn't trustworthy how can another set up using the same or another sensor plus a gauge be trusted? And why remove the sensor from the system? Why not put in a bypass switch to use should it be needed? Let the stock system work until there is evidence it isn't.

If you look in the manual, the information on water temp for switches to work is kind of surprising - how low they are working. This is also information you should know if you want to operate your cooling system manually.

• Fan switch: rising temps switches on 201-212 degrees, as temp drops it will go off 194-199 degrees. So clearly the cooling system is keeping the temperatures pretty low since few seem to have the fan come on very often.
• Temp light switch: rising temps switches on around 225-236 degrees, as temp drops it will go off around 217-223 degrees Again, well within safe ranges.

It is not a problem for vehicles to run upward of 230 degree water temps from all research I've seen. Fact is when Kawasaki had some high temp readings on Ninja 600s the fix was to add a resistor lowering the gauge reading. The actual coolant temp was totally acceptable and Kawasaki had stated they had no problem with coolant temps spiking up to 260 degrees. One interesting thing I found while looking was that NASCAR racing has cars running constant coolant temperature around 220 degrees... for several hundred miles at near red line.

Here is a quote attributable to a reliable source - Motocross Action Magazine:
"How hot does an engine run? The hottest spot on your bike’s engine is the head pipe. It runs at 1200 degrees (with hot spots that verge on the 1300-degree melting point of mild steel). The rest of the pipe warms to 600 degrees (so don’t touch it). Cylinder temperatures are also in the 600-degree range, while the water temperature should vary from 200 to 300 degrees (the closer to 300 the closer to catastrophe). Most race teams would like to keep their basic water temp below 200 degrees if possible." No internet hype, none of the "it must be true, it's on the internet", rather a comment from a reliable source based on actual practice by manufacturer racing teams in the toughest of conditions. They are not in risk of running too cool, but rather too hot and they are looking for optimum temp. Here is the article in full context.

From that you can see the KLX250 sensors and cooling system are essentially tuned for maximum efficiency. From everything I can find the most common general operating range for virtually all four stroke engines is from 190-200. Too cool makes for condensation inside the engine - heat "cooks off" moisture. Extreme cool can cause extra wear - the reason why there is the claim that most wear occurs at start up/warm up. The reason there is a thermostat.

If you are really concerned, consider using Engine Ice coolant claims to not boil up to 256 degrees, so that is a consideration since boiling over or turning to a gaseous state in the jackets is the problem, coolants like that are a solution to minimize risk if you do run hot. We sold a lot of that and WaterWetter for off road riding and sport bikes, when I was working at the dealership.

Am I saying don't add oil coolers or manual switches? No, just saying research and know what and why to do something. Is it really needed or is it personal preference. If one asks do they really want an answer or just reinforcement of a decision made. Some people want max control over everything or maybe just a few. I do when I need to, but seldom just because. Heck it's kind of like the tensioners I make. I tell people if there is no rattling they don't need to go to the manual one. If the rattling does start they have a few thousand miles before it will start affecting things. Some decide to wait, others decide to make a preemptive strike - replace before needed. Will it fail on every KLX? I don't know, but the numbers say it happens a lot. The fan failure thing isn't as easy to figure. With a Vapor set up that would give some good information a bypass switch a safety net should a sensor fail. But doing it "because" without any way to judge when to run the fan just doesn't make mechanical sense.

If you like gauges, totally understandable, do it for sure. I like gauges in some conditions, mostly automotive. I hate idiot lights. One cost me a cylinder head on a turbocharged Plymouth. By the time the idiot light lights up it is too late, a gauge would have shown the temp rise in time to save the head. As I comment on this I think it would be great if there was a temp gauge in the instrument pod. Not like that would be tough to do. I'd actually give up the tach to have something of value like the coolant temperature - at least on a single.

 

No preparation is needed. As long as the oil is clean and the bike is in tune, it will run high rpm forever, no problems.

 

Trail tech is a brand. Google it.
See the FAQ link in my sig line and search that page for "fan." You'll find instructions for a bypass switch. And, no, it doesn't bypass the stock fan sensor; it still works.

 

...thanks , I'll take a look and maybe give it a shot.
Cant work on the bike till next week though because I have final exams coming up. boo