overheating problem please help!!

[texasman20]

So i bought my 400EX about 4 months ago and have always had a little suspicion that it was running to hot but couldnt tell for sure until i installed my vapor. i went out today and ran a little trail near my house. first run went good. rand about 210-220 but the 2nd pass i was messing around on a little MX track just putting around and jumping and looked down and it was at 290 so i figured it just wasnt happy cause i was going slow so i speed up and continued on looked back down and i was going 30mph and it was at 349!!! it was 71 degrees outside. What is the problem?? PLEASE HELP

[mmbintn]

How do you have the temp probe installed?

[bergoff]

i would check your temp probe

[texasman20]

It is just the type that replaces the crush washer at the plug. Not sure how I could have screwed that up...

[mmbintn]

You actually got it to fit down there? I hooked mine up to the exhaust stud. I regularly run above 300 but that's on the exhaust port so I figure its good. Make sure your wire does not touch the pipe as it will give the reading off the pipe. I don't know what the temp should be at the plug as most everybody gets there reading from the oil temps which I assume will be much lower. I figure if my header is sitting around 320 then the oil itself will be in the mid 200's.


Originally posted by texasman20
It is just the type that replaces the crush washer at the plug. Not sure how I could have screwed that up...

[texasman20]

I talked to the local honda guys after i went riding the other day and it jumped up to 400 (yes 400!) and he said i should not be concerned about that kind of temp right under the plug because it is so close to the combustion chamber. What do you guys think? i am still very concerned......

[bergoff]

if i was you i would try to get it read oil temps. i wouldnt worry about your temp reading off of the plug.

[Bill Martin]

I don't think you have anything to worry about. If there was any problem with the 400 overheating they would have address the problem long ago. Just keep the mud and dirt off the motor and you'll be ok. I take a 2 gallon pump up sprayer with water in it and it makes a handy way to clean off the motor when you get back to camp. At some off ower races this summer here in Texas it was 105* or better and I ran lots of 30 minuet moto's with no problem. The real threat to over heating when it's that hot is when you stop; even if you shut the motor off the temp will continue to rise for a few minuets.
I use a fan to cool it down after a moto.

You’re running a stock 400 and unless it’s covered with mud your ok.

At least you're paying atention to it.