STUMPPED!! 2005 KYMCO Mongoose KXR 250 OVERHEATING????

[BOSOX5150]

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 its 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 its not really hot or its 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??

[JOHNDOE83]

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 its 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 its not really hot or its 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??


Sounds 100% jetting related

Anything else you mentioned would have to be custom made.

Try ebay for new parts, its the best option, don't count on any aftermarket parts unless you custom make them.