What tempature should my rmz 450 run at? Also why does my header pipe get red hot after running for only five min. at idle?

The cooling system on the RM-Z450 was designed for motocross and only works efficiently with air flowing through the radiator. You should not sit at idle for more than a minute or two if at all possible. The extreme high output of this engine causes extremely high exhaust output temperature. The pipe temps can reach 600-800 degrees F plus all the way back to the silencer. This is normal on all modern racing 4-strokes. There are a lot of aftermarket products available that help increase the cooling system efficiency. There are also several products that help insulate critical areas from engine and exhaust heat including shields for fuel tanks/lines, the carb/throttle body, rear shock, and plastic body work.

It dont matter how long you let your bike sit at a dry idle, the pipe is at noe time supposed to get red hot. your problem is your exhaust valves, they need to be tightened. having lose exhaust valves will cause the your valves to improperly ceet around the mouth of the chamber and un burnt fuel is shot out the exhaust. thus firing flames directly at the head curve of your head pipe will cause it to get red hot.

Well, first of all, the bike sould run around 200-220, at least that is when the fan comes on on most quads and streetbikes.

As far as the pipe, they all usually glow red hot, especially when they are stock. usually they come really lean from the factory and could use an increase in the pilot jet size, or pilot screw adjustment. Richen it up as this will usually take care of that.

Also, these four strokes can't sit and idle for more than a few minutes or they overheat, and puke coolant out the overflow hose. you need air to be flowing over the radiator to prevent this.