i was out on my 01 400EX the other day and i was riding it for a bot a half an hour, i was climbing some rather large hills... and then stopped and got off and notcied my 2 head pipes were glowing red?? i figured it was because of improper stock jetting for the colder wheather.. it was def. below 30... and i got home checked my plug anbd it was also red... what should i do>? or what is the problem, my 400 ex is stock, with the spark arrestor out. any help would be appriciated! thanx

01 400EX Yellow

 

Next time take eggs and bacon

 

jet the main jet higher... you are running lean... especially up hills..When I run at the Dunes I run a 180 when I run MX I run 170... YOu are really on the motor hitting those hills... Jet it up a couple sizes

 

especia;lly with the cold air now, iusnt the air thinnerso i should rejet it anyway... what size do u suggest for me?? thanx for your help too!

01 400EX Yellow

 

It's the sparky bein' removed. Bring the main jet up a size or two.

 

that will do it??? i didnt really think the spark arrestor did anything exept for sound and well... to protect sparks.. what size is it stock? i am getting a wb silencer soon... should i just wait until then to get it?? it wont hurt my 400 now by it running lean will it??

01 400EX Yellow

 

humm i think stock is 148...i dunno i have a dyno jet kit..maybe a 152,158..maybe higher

 

I believe the air is actually thicker-ie. more dense in the winter. This is why you have a hard time breathing when it is cold. ............But I am not a science major.

 

True..Colder up the size...Warmer lower it

 

My 2000ex pipes have always glowed red. Not in the day time. If it is getting dark all of my friends pipes glow red, its because they are thin and hot. I don't think this is uncommon or that you have to re-jet to fix anything. And to add one thing, put your spark arrestor back in, it will look, sound, and run better. If you look at dynos where they have tested HP with stock ex's the spark arrestor only made the HP jump around a bunch, it's not as smooth flowing. The HP didn't go up any. Later