07 525 EXC Heat Issue

I know there are tons of threads and did my searching but I have a few other questions. Lately I've been forced to race my dual sport due to bike issues. I know these suckers run hot from the production line but what the hell... What are you guys doing to keep your bike cool under race conditions? I normally race a mid pack A class race pace running hare scrambles. Currently my bike is setup with engine ice, uncorked exhaust, no emissions bull, uncorked thermostat, and JD jet kit. I can't keep this bike from steaming over. I'm waiting on my fan to come in but can't see that really solving my issue. I jetted the bike according to the instructions but just curious what you guys are running around South Jersey. What else should I be doing (over sized rads, larger water pump)? The only way I can keep this thing cool is to cruise around 20mph with a steady throttle on the trail. On the street you can rip it all day with no issues, obviously getting more air. It seems to be the slow stuff. Also I tend to be getting a ton of clutch fade in just a single 7 mile lap. Normal for these bikes? What kind of mileage or hours you guys getting out of these clutches on dirt/street?

Any help would be greatly appreciated and yes I'm a KTM newb if you couldn't tell.

To keep these engines running cool enough, they definitely need proper jetting, free flowing rad guards and a fan for slow going. Make sure not to overfill the rad, or better yet use a (homemade) coolant recovery system.

The KTM clutches are very long lasting unless abused by too much clutch slipping.

Sounds to me like you are having to slip the clutch which generates a lot of heat and leads to clutch fade.

What gearing are you using?

This assumes you have correctly bled and filled just covering the tubes, not to the brim, and the coolant level is below the tubes at race end.


Sounds like you need the coolant over flow bottle Chas mentioned.

I have the same bike in the 450 model. with 13/50 sprockets and the fan kit. Never had it boil over... ever.. the fan does run a lot. I do a lot of hard single track under hot conditions. I rarely have to slip the clutch with that low of gearing.

I'm running 13/50 gearing and I am probably over clutching a little bit, but never have had a problem with anything else.

Yes I have bled and filled correctly.

I'm running 13/50 gearing and I am probably over clutching a little bit, but never have had a problem with anything else.

Yes I have bled and filled correctly.

I'm at a loss for ideas.

95% of the RFS overheating threads are due to:

1) Overfilling, the coolant expands and the excess is pushed out the vent and is mistaken for boiling over, therefor not really overheating.

2) Jetting, which you have addressed.

3) Gearing, which you have addressed.

The other 5% are riding in extreme conditions or have some other mechanical problem.

Some radiator guards do an excellent job of restricting airflow.

I personally use and swear by Evans non-aqueous coolant which is rebadged and sold by Zip-Ty. It has an incredibly high boiling point and not containing any water Evans doesn't expand so the cooling system operates at zero psi. The down sides include price/availability and it doesn't transfer heat quite as well as water/antifreeze mix so engine runs very slightly hotter if thermo is full open or there isn't one. Evans should not be used to mask other problems, only use on engines known to be operating correctly because it will not boil over at anything like normal operation.


I ride enduros on the east coast with an 07 525. Run pro cool, 13-50 gearing and the fan kit. Fan will run a lot but bike does not over heat. I would suggest up sizing the battery with the fan. Cant remember what I have for jetting, B&B jetted the bike when I bought it and havent had to mess with it. Im on the road wont be home untill later this week if you dont figure something out let me know and I will check my jetting. Also check the valves if they are tight the bike will tend to run hot.

The bikes head may not be bled correctly.

The bike needs to be leaned over way past the side stands normal lean and the bleed bolt loosened.

Secondly the jd jetting sounds like it may not be rich enough. I use regularly available kehein jets and needles direct from Sudco.

I always retain the thermostat.

No guards in the radiator other than the factory guides.

Is there a dark residue in the intake tract? The intake valves on the 07's were especially soft and are leaking hot gases back into the intake tract causing the oil stains in the intake and causing heating issues due to loss of the cooling effect from the fresh air/gas charge coming in. They start to leak at 100 hours and are fairly worn out at 175 hours.

Are you sure the fuel screw is correct? Screw, spring, washer, o- ring in that order.


Edited by caflashbob
Added comments

Stay off the clutch. That is the main reason for overheating. You have 525 and the gearing is low enough you shouldn't need to use the clutch much at all.

I'm running 13/50 gearing and I am probably over clutching a little bit, but never have had a problem with anything else.

Yes I have bled and filled correctly.

How many hours?

Pull the carb and see if the intake shows darkening.

If I were there I would walk up to the bike running and see how strong the pulses coming out of the pipe are.

If you cover the end with your gloved hand does the exhaust push your hand off.

The 07's must have used up the soft old stock intake valves at the factory.

Well rounded at 170 hours. Normal was 300-400 hours.

How are you adjusting the valves? Feeler gauge or 1/6 turn from tight?

The bottom of the feet cup and then a feeler gauge is incorrect clearance.

1/6 turn from zero clearance on the adjuster is .005 clearance.

Compare the feeler gauge to the 1/6 and the extra turning is how much the adjuster foot is worn.

Doc bob

Have you ever replaced the rad cap? I put a new one on mine about every 12-18 months when it seems to start heating too easy. I'm still using the 1.4 cap but lots of others (including KTM on the newer bikes) have switched to the 1.8 cap.

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