WR450 Hot at Idle??

Hi There,

I have a brand new 2009 WR450 that I scooped up. I've ridden 2-strokes my entire life and this is my first 4-stroke, Ever! I'm excited.

Havent ridden it yet but I did just put on the AIS block off, throttle stop & JD Jet Kid (168 Main, Stock Pilot, Red needle 4th clip, fuel screw 1 1/2 out.. I'm at Sea Level). Fired right up and idles fine. HOWEVER.....

I've noticed that within 1 min at idle the pipe is red hot and so is the radiator and cylinder. Now I've always been on a 2-stroke and it takes a long time at idle to warm things up... is this normal on a 4-stroke?

Also.. off topic but on the AIS blockoff is there supposed to be a gasket or anything between that machined plate and cylinder?

Thanks in advance!

red hot header means the bike is lean, which means your pilot jet is prob off or plugged. and since it is stock, i say it needs to be changed to the correct pilot jet. maybe try a 48 pilot?

Thanks for the quick response. I guess I should re-phrase... How hot is too hot at idle? I'm used to a 2-stroke where 5min and the pipe would only be luke warm.

Essentially whats a normal temp at idle?

Once you get some air flow the head pipe will cool down quickly. Don't let it sit and idle for long periods, it needs airflow. Both of my WR's have JD kits and run great, but if they sit there idling the head pipe does get red. It sounds like you followed JD's instructions which in most cases will get you very close. If the bike runs well I say leave it alone and keep the idling to a minimum.

Hi There,

I have a brand new 2009 WR450 that I scooped up. I've ridden 2-strokes my entire life and this is my first 4-stroke, Ever! I'm excited.

Havent ridden it yet but I did just put on the AIS block off, throttle stop & JD Jet Kid (168 Main, Stock Pilot, Red needle 4th clip, fuel screw 1 1/2 out.. I'm at Sea Level). Fired right up and idles fine. HOWEVER.....

I've noticed that within 1 min at idle the pipe is red hot and so is the radiator and cylinder. Now I've always been on a 2-stroke and it takes a long time at idle to warm things up... is this normal on a 4-stroke?

Also.. off topic but on the AIS blockoff is there supposed to be a gasket or anything between that machined plate and cylinder?

Thanks in advance!

Come on, you are saying the the pipe, cylinder, and radiator are glowing red?

All four strokes run much hotter than two strokes.

^^ "Red hot" can often be a euphemism for something that is just really really hot..

But yes, my WR's header will glow a bit red in low light conditions if it is left idling, as soon as you get some air flow to it and the radiators it's not a problem.

Also check the coolant, when I got mine (mine was older, used, but still this may make a difference) the cooling system was mostly water with little coolant and the radiators would be burning hot after barely being started. After flushing that out with a decent coolant mix it takes longer for it to warm up.. Might not apply to your new bike though, just sayin' :busted:

haha i had the exact same prob with my 450 (tho it was an rmz) they can get very hot and even boil over if left idling for a short length of time, I took mine out for the first ride and it ran nice and cool...due to the higher compression etc 4 stroke run WAY hotter....dont let it sit and idle for too long! about the jetting...it sounds about right...just change that pilot :)see how ya go....

Also.. off topic but on the AIS blockoff is there supposed to be a gasket or anything between that machined plate and cylinder?

Thanks in advance!

I don't know what AIS blockoff kit you purchased, but my F2Racing kit (AIS blockoff) came with a metal gasket. I would think not having a gasket would cause an air leak. My Header will glow a bit when hot up near the cylinder, and is perfectly normal on these bikes. I would not recommend idling your bike for anything more then a couple minutes, without placing a fan in front of your rads. I just place a household fan in front of it when I need to run it for awhile to diagnose a problem, or adjust the fuel screw.

Thanks for all the responses. Yeah I bought the GYTR AIS kit and it did not come with a gasket. So I too was/am worried about a leak,

Thanks for all the responses. Yeah I bought the GYTR AIS kit and it did not come with a gasket. So I too was/am worried about a leak,

I re-used the gasket that was under the original AIS port flange.

I had the same problem. I jetted by jd jet kit instructions and had glowing red, popping on decell, so i went one bigger on the primary. The bike has to sit for a long time before i get any red in the pipe.

iI was told about a larger water pump for my yz450f but cant remember that maker any body know a good one

iI was told about a larger water pump for my yz450f but cant remember that maker any body know a good one

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