Exhaust gets extremely hot and heats the chassis too much. Help!.
#21
07-16-2016, 07:15 PM
Solution
Hi Guys,
I am Kratos who initiated the topic, but I had some issues with my user and password and opened this new account.
I have good news after a couple years dealing with the high temps issues, I found the problem, it was the jetting of the carb itself. Last time I wrote here I was waiting for the Powercore 4 slip-on exhaust, well, I installed it expecting to solve the problem but by the contrary the problem got worse, even to the point the exhaust pipe was glowing red at night and the heat radiated to my right leg was too much even using jeans. I took a ride in other KLX 250s but there was not such amount of heat like in mine. Si, I figured out it was something really not normal in my bike.
By accident recently the motorcycle started popping up when deaccelerating and one day the IDLE got crazy and each time I stopped the motorcycle was at 4000 RPM for so long before to get back to normal. In that moment I figured out a review of the carb was needed and then I took the opportunity to buy a Dynojet kit to reject the bike while cleaning and checking carb. In that way we installed stage 1 configuration using a DJ120 main jet, drilled the Air mixture screw, set it to two turns (since I am at 425 Meters Above Sea Level) and washed the carb with paint dissolver.
After that I went out to test the bike and the results were:
• IDLE problems were fixed. No oscillations.
• The temperatures now are pretty normal and it is comfortable to ride the bike (even in shorts).
• The popping up has almost disappeared.
• The acceleration is smooth and when deaccelerating the motor brakes the bike.
I took the time to share this experience, since I was frustrated for so long and due to the complex process to dismount the carb I always tried to point to other parts but the problem was always there.
I think the dealer sold me the bike with some sticky old bio-gasoline and from the very beginning the carb was not working properly.
Now I am starting to really enjoy my bike and hope this will help to somebody else in the future!!.
Best regards,
Kratos/HornedF
I am Kratos who initiated the topic, but I had some issues with my user and password and opened this new account.
I have good news after a couple years dealing with the high temps issues, I found the problem, it was the jetting of the carb itself. Last time I wrote here I was waiting for the Powercore 4 slip-on exhaust, well, I installed it expecting to solve the problem but by the contrary the problem got worse, even to the point the exhaust pipe was glowing red at night and the heat radiated to my right leg was too much even using jeans. I took a ride in other KLX 250s but there was not such amount of heat like in mine. Si, I figured out it was something really not normal in my bike.
By accident recently the motorcycle started popping up when deaccelerating and one day the IDLE got crazy and each time I stopped the motorcycle was at 4000 RPM for so long before to get back to normal. In that moment I figured out a review of the carb was needed and then I took the opportunity to buy a Dynojet kit to reject the bike while cleaning and checking carb. In that way we installed stage 1 configuration using a DJ120 main jet, drilled the Air mixture screw, set it to two turns (since I am at 425 Meters Above Sea Level) and washed the carb with paint dissolver.
After that I went out to test the bike and the results were:
• IDLE problems were fixed. No oscillations.
• The temperatures now are pretty normal and it is comfortable to ride the bike (even in shorts).
• The popping up has almost disappeared.
• The acceleration is smooth and when deaccelerating the motor brakes the bike.
I took the time to share this experience, since I was frustrated for so long and due to the complex process to dismount the carb I always tried to point to other parts but the problem was always there.
I think the dealer sold me the bike with some sticky old bio-gasoline and from the very beginning the carb was not working properly.
Now I am starting to really enjoy my bike and hope this will help to somebody else in the future!!.
Best regards,
Kratos/HornedF
#22
07-16-2016, 08:15 PM
I keep seeing posts talking about "rejecting" the carb. 
You are not rejecting the carb, you are re-jetting it-- I, on the other hand, actually "rejected" my carb and decided to purchase another one. Still not clear on what caused the "4K sputter" but I now believe its slide/diaphragm related.
In any case - anywhere near sea level a 40 pilot jet and Kouba fuel screw are essential. I had to re-pilot the KLX 300 carb I bought due to decel popping, erratic idling and hard starting. The 40 pilot and ability to dial it in while running made all the difference. Went for a 40+ mile ride in woods and forest oil field roads and fan RARELY kicked on-- and when it did it wasnt for very long.
Bike runs like an animal now, smooth from bottom to top and back to bottom. Hard hitting midrange. Aside from what feels like a spark cut out every so often when nearing the top of 5th and sometimes under hard accel nearing top of 6th, its perfect.
You are not rejecting the carb, you are re-jetting it-- I, on the other hand, actually "rejected" my carb and decided to purchase another one. Still not clear on what caused the "4K sputter" but I now believe its slide/diaphragm related.In any case - anywhere near sea level a 40 pilot jet and Kouba fuel screw are essential. I had to re-pilot the KLX 300 carb I bought due to decel popping, erratic idling and hard starting. The 40 pilot and ability to dial it in while running made all the difference. Went for a 40+ mile ride in woods and forest oil field roads and fan RARELY kicked on-- and when it did it wasnt for very long.
Bike runs like an animal now, smooth from bottom to top and back to bottom. Hard hitting midrange. Aside from what feels like a spark cut out every so often when nearing the top of 5th and sometimes under hard accel nearing top of 6th, its perfect.
#23
07-17-2016, 02:53 AM
Thank you Josh, you are right there were typing mistakes. Actually I wrote the post in Word and it autocorrects that. While I was writing this I wrote rejetting and it happened again. Apologies about that.
On the other hand, I am interested on the Kouba screw you mentioned. Where did you get it?.
On the other hand, I am interested on the Kouba screw you mentioned. Where did you get it?.
#24
07-17-2016, 03:16 AM
#25
07-17-2016, 02:43 PM
Personally I am using the stock KLX300 bits in the 250 carb. I have the modifications listed in the KLX250 cheap mods link in my signature. I mentioned adding the Dial-A-Jet fuel adder to compensate for any lean spots.
#26
07-20-2016, 05:32 AM
I have an EFI model - but do tell, what is this 'air injection' thing of which you speak?
My rear muffler does get VERY hot, hot enough that any water touching it instantly sizzles and steams - which I'd expect from the header pipe, not the muffler.
Clearly the cat is causing the issue, but if there is some easy mod I can do to reduce that heat I'm all for it?
See attached photo for what happened to my leg on the KLX150 after changing the exhaust, which didn't come with a heat shield. I added one after that!
On my 250 the MUFFLER is hot enough to cause a serious burn, so yeah, if I can reduce that without buying another exhaust for now, please explain how?
My rear muffler does get VERY hot, hot enough that any water touching it instantly sizzles and steams - which I'd expect from the header pipe, not the muffler.
Clearly the cat is causing the issue, but if there is some easy mod I can do to reduce that heat I'm all for it?
See attached photo for what happened to my leg on the KLX150 after changing the exhaust, which didn't come with a heat shield. I added one after that!
On my 250 the MUFFLER is hot enough to cause a serious burn, so yeah, if I can reduce that without buying another exhaust for now, please explain how?
#27
07-20-2016, 11:09 AM
I don't know what you guys expect. It's an exhaust pipe. They get hot. Exhaust gasses come out of the cylinder around 1300-1700 degrees F. Every exhaust system gets hot enough to burn and blister you. My wife made the mistake of touching a muffler on a 1982 Honda CB900F, burnt the tips of her fingers pretty good. That's a double wall system.
Every bike you see with blued chrome or that golden multi-color on stainless means the exhaust has been quite literally several hundred degrees F, hot enough to glow! The manufacturers have used double wall pipe on chrome to avoid bluing - yet some riders let their bikes sit and idle, causing even a double wall to start to blue - and now are using separate heat shields that still get hot enough to severely burn a person, but won't blue.
Get rid of the pollution equipment and now the exhaust is maybe 1100-1300 degrees F at the head. You cannot get any of your exhaust system cool enough to touch when at full operating temperatures anywhere on it. Pollution equipment or catalytic convertor removed or not, just ain't gonna happen. Fact of life.
You can wrap the muffler or sections of an exhaust with the exhaust wrap to help. Performance car parts sources sell it for sure. It may insulate enough to avoid burns, I don't know for sure.
Otherwise you need to get an electric motorcycle if you can't take the heat. It is a characteristic of the internal combustion engine.
Every bike you see with blued chrome or that golden multi-color on stainless means the exhaust has been quite literally several hundred degrees F, hot enough to glow! The manufacturers have used double wall pipe on chrome to avoid bluing - yet some riders let their bikes sit and idle, causing even a double wall to start to blue - and now are using separate heat shields that still get hot enough to severely burn a person, but won't blue.
Get rid of the pollution equipment and now the exhaust is maybe 1100-1300 degrees F at the head. You cannot get any of your exhaust system cool enough to touch when at full operating temperatures anywhere on it. Pollution equipment or catalytic convertor removed or not, just ain't gonna happen. Fact of life.
You can wrap the muffler or sections of an exhaust with the exhaust wrap to help. Performance car parts sources sell it for sure. It may insulate enough to avoid burns, I don't know for sure.
Otherwise you need to get an electric motorcycle if you can't take the heat. It is a characteristic of the internal combustion engine.
Last edited by klx678; 07-20-2016 at 11:17 AM.
#28
07-20-2016, 01:29 PM
Nope, I have to disagree, it's not normal for the muffler to be so freakin' hot.
On my 150, which burned my leg after a mild tumble (KTM falling in front of me, again...) I swapped the whole exhaust for an after-market one, so cannot say what the original was like. But I do know that while the header (manifold) pipe was obviously very hot and burned me, the muffler was not.
You wouldn't want to play with it for any length of time but you could touch it for a second or two.
In contrast the original muffler on my 250 is plenty hot enough to burn you if you were to touch it at all, even for a fraction of a second. Considering it's right next to the legs of a pillion passenger that has to be considered either a design fault or the bike not running properly or something.
So yeah, if there's some tube somewhere I can plug that will reduce the temp' of that thing then I'm all ears?
By the way, while talking to people about panniers for the 250 I've heard 2, count them, that's 2, stories of panniers actually catching fire on a KLX 250. That cannot be considered normal.
On my 150, which burned my leg after a mild tumble (KTM falling in front of me, again...) I swapped the whole exhaust for an after-market one, so cannot say what the original was like. But I do know that while the header (manifold) pipe was obviously very hot and burned me, the muffler was not.
You wouldn't want to play with it for any length of time but you could touch it for a second or two.
In contrast the original muffler on my 250 is plenty hot enough to burn you if you were to touch it at all, even for a fraction of a second. Considering it's right next to the legs of a pillion passenger that has to be considered either a design fault or the bike not running properly or something.
So yeah, if there's some tube somewhere I can plug that will reduce the temp' of that thing then I'm all ears?
By the way, while talking to people about panniers for the 250 I've heard 2, count them, that's 2, stories of panniers actually catching fire on a KLX 250. That cannot be considered normal.
#29
07-20-2016, 08:18 PM
Feel free to go grab a few motorcycle mufflers. Your hands will look like your leg did. It's not like I'm exaggerating. You do realize if mufflers didn't get hot enough to boil off moisture they'd quickly rust out, right?
Good luck on the Quixotic journey. Click on the cheap mods link in my signature you will find a section on removing the pollution system. But don't be surprised if you still can burn the hell out of yourself. It's an exhaust system, a HOT exhaust system.
If you really want to try to do something effective do the wrap on the muffler. It is an insulating wrap. It will reduce surface heat more than the pollution system removal.
Good luck on the Quixotic journey. Click on the cheap mods link in my signature you will find a section on removing the pollution system. But don't be surprised if you still can burn the hell out of yourself. It's an exhaust system, a HOT exhaust system.
If you really want to try to do something effective do the wrap on the muffler. It is an insulating wrap. It will reduce surface heat more than the pollution system removal.
Last edited by klx678; 07-20-2016 at 08:20 PM.
