So I just picked up a 2005 Kymco Mongoose KXR 250 from a dealer (SAME AS ARCTIC CAT DVX 250) & quickly realized the term “as is” sucks! After about 20 min of riding it seems to be running excessively hot. It lets out a long sigh of relief after shutting it down (about 2 min after) which sound s like someone partially opening a radiator cap on a hot engine (don’t do that) however I cannot see any steam or leakage or locate for sure where it’s coming from but I do believe it’s around the top of the head. So I put a thermal strip on the head and sure enough after about 20 minutes it hits the highest reading (240) which is about 60 degrees above my 3 other machines. So sure this could be normal for this make/model (anyone?) but there are other issues I feel are from this heat. First the plastic is melted right through just behind where your left thigh would be about 6” before the silencer. I’ve heard other Kymco owners say they have had melted plastic here but not all the way through. The plastic was brand new, replaced by the dealer. Also the head pipe is chalky white and rust colored from the cylinder most the way back to the silencer which I do believe is stock (head pipe) but the silencer is aftermarket. So melted plastic, dis-colored pipe, release of air after shut off and hits 240 degrees after 20 min of riding are what concern me. I don’t really know if this is overheating for this machine or not. It does run fine, starts easy and has no power loss even when it reaches the 240 but we do shut it down immediately at that point. I checked the coolant and it’s filled and never goes down. No coolant on the oil obviously or it would be low in the radiator. The pump must be circulating or it wouldn’t take 20 min to hit this temp. (I’m in Florida by the way so it’s hot out and sea level). I also checked the temp after the water pump with an infrared temp gun and its reading 240 like the cylinder which the fluid in the radiator wouldn’t do if it hadn’t passed through the engine. I did a leak down test and only had a 2% loss (if I did it right) and did hear a little hiss around the valves but I had the cover off (is that ok?). I haven’t checked the clearance yet as I don’t really know how but I will learn ASAP! I did blow through the spark plug wire and it wasn’t clogged. Just kidding! I wired the fan to a switch to ensure it was running just to troubleshoot. I know this is not good permanently; this was just for a test. Still hot! I ordered a thermal switch for the fan and a thermal sensor for the temp light which btw has not ever come on (either it’s not really hot or it’s not working? idk??). I ordered a thermostat too just to be safe but water is circulating. So what’s left?? I opened up the air box so it can breathe good and ordered new jets of various sizes but there not here yet. I did have a similar issue with a crf150r and jetting did fix it. But I don’t know if that’s the issue here, it is a bit more excessive in symptoms. The crf just ran hot and let out steam from the case breather, no melted plastic or chalky white pipes! The temp strip did hit 240 though. I’m going to Hatfield McCoy in 2 weeks and don’t want to chance it that this is normal. With that said if jetting is the issue then my stock jets may be fine in the mountain elevation since in Florida all my bikes need to jet up a step from stock but at mountain elevation you want to step down a size which is where it is now. I don’t want to wait to get there though to see if this is the issue in case it’s not. I will try to re-jet when they arrive (this week I hope) and just do it again if needed when I get to West Virginia. Anyone have any ideas or know if 240 is the normal temp for this ATV? Anyone had this issue? Could it be jetting or is it fine? What else is there?? Anyone, anyone? I would like to put in a hi flow water pump like the pro circuit, boyseen or outlaw impeller but can’t find them for this machine. I’d also like an oversized radiator but same thing, there’s none! Anyone know of any that will work??

 

Kind of hard to say, but a couple of thoughts. The waterpump impeller could be slipping on it's shaft allowing only some flow, and the other could be a clogged radiator. When hot, use your laser thermometer to measure the radiator temps on it's sides, top and bottom, and in it's center with the fan switched off. Then switch the fan on and see if the center of the radiator gets cool. Radiators tend to clog in the center and still flow well around the outer edges.

Greg

 

Thanks, Great advise I ckecked and the entire cooling system is caked with rusty sludge and black powder substance. I am in the process of flushing it out and hoping this resolves my issue. Thanks again!

 

I would be sure your tank is venting properly. Its possible the tank is sucking air when you shut it off because it isnt venting properly, which would also make it lean, which could cause the overheating. Worth a look at least.

 

I think that's a good idea. That might explain the "sigh" LOL.
It has to be something stupid like. My Kymco ran thru 2-12 hour races, countles woods riding hours, a few MX nationals and a cpl XC races. Tranny gears failed but the motor is bulletproof.

 

So I flushed the radiator and viola its fine! THANKS for the advise NOVA, I'm not sure if you where refering to the external fins or the internal passages when you said "it may be clogged" but either way it provoked me to check just how well fluid was flowing through it inside. Sure enough the rusty sludge was the cause, I flushed it and replaced it with engine ice and it never broke 160 degrees even when idling for 20 min! Although I did end up wrenching for 5 days on my sons drr 90 on our trip to HMT which was horrible. I gave up with 2 days left and came home never putting in more than 5 miles of riding. I took an 1800 mile round trip to do what I do in my garage all day!

 

Arctic Cat sure made that 250 ATV more complicated then need be.
With a small 250 a air cooled with a oil cooler would of been fine. Even without a oil cooler it would of been fine since there are so many 250 even air cooled "without oil coolers" ATVs and ATC that are over 25 years old running around.

Think of the headaches Air cooled removes, water level, water pump. thermostat, rad, fan, thermal sensor fan switch,rad hose,rad cap and possible air locks and water seal leaks.
I can see higher powered big bores needing liquid but not a 250.
My 1987 250 Yamaha Moto4 with no oil cooler is still running strong and never had a rebuild. I just do not think she would of had the same luck with all the liquid cooled above parts added on.

My 1989 350 4x4(still going great), 2007 350 Grizzly ,2000 450 Foreman are air cooled my friends 500 Honda Foreman is air cooled I just do not get why a 250 would need the complications of liguid cooling.

 

hehe