Grey Wire mod = heat

I recently cut the wire on my bike and have been reaping the benefits. But lately I have noticed that when I have been riding it hard, it gets hotter than it ever used to. Hot enough that the headers glow bright red at night. Is this normal? Abit paranoid since a friend of mine recently had an engine seize on him because of heat. Sure its nothing, but i've never seen my XR (yes as in honda) get that hot before.

I've collected some "Gray Wire" data on my WR250F (A report should be appearing in the soon to be released tech section of TT) and can make the following comments...

The WR250F gray wire retards the ignition timing by as much as 30 crank angle degrees - at mid throttle and engine speed greater than 7000rpm. Retarding the ignition timing from its optimum point delays the combustion process. This does two things: 1) The engine produces less brake power and 2) The lost brake power is dumped down the exhaust as heat - the flame front may actually propagate out through the open exhaust valve during the blow down process.

Your bike would tend to have much higher exhaust gas temps with the gray wire CONNECTED. It is the exhaust gas temps that are causing the header to glow.

Elevated exhaust gas temps may or may not raise the coolant temp - this depends on cooling jacket design in the exhaust port area.

I believe the night time exhaust header after glow is common, at least it is on my bike - especially at idle where the ignition timing is very retarded relative to optimum.

The WR headers glow red from stock.

Originally posted by *mike68*:

The WR headers glow red from stock.

I concour. It is not from the mod. It is just that way.


If life is not a blur. You aren't going fast enough

Scared me the first time too.

Must be a thumper thing.

My V-Twin Suzuki TL1000R has the same problem. My buddy and I noticed it while riding at night. Come to find out, it is normal. Thinner wall header construction for weight savings and bare metal instead of matt black finish probably make it more noticable.



2001 WR250F

White Brothers E Series Full exhaust

Panoram computer

Fly bars

jet kit

YZ timing I think (bought used)

Grey wire mod


just for me, would you tell me your needle code, PJ, PAJ and PScrew how many turns out?


Maybe it's just that I am riding more often in rougher terrain with less speed lately, but it sure seems my "00 WR 400 boils easily since the grey wire mod. Never heard it boil before, regardless of how hard I rode it. In open desert, the wind in the radiators keeps it cool even when the throttle is pegged and repeatedly accelerating hard out of turns and through washes for 15 min or more.

I have heard the mod actually advances timing in midrange. Sounds logical to me that it would run hotter. Anyone else have this experience?

you guys are touched............the grey wire has nothing to do with heat BUILD UP......

Originally posted by Ga426owner:

you guys are touched............the grey wire has nothing to do with heat BUILD UP......

If YZ timing is used at slow speeds it will cause more heat. Straight from Randy Hawkins.

I have a buddy who just got a WR 400 and has cut the throtle stop and removed the baffel from the stock pipe but thats it. What other modes should he do to keep up with my KTM 400? Is there a air box mod? Jetting? And last but not least where is the grey wire and what benifits do you get? THANKS TO ALL YOU BLUE OWNERS

I havent seen a Wr that Doesnt Glow at the Header. I did notice the pipe glows MORE with the baffle in place though. Im guessing that the backpressure is holding more heat in the entire system and of course the thin walled stainless header is going to glow like crazy for all the heat that isnt escaping as fast as if the baffle were removed. Also, Just a warning.. If you ever replace the header with a Non stock SURE that your muffler to Header pipe (located by the kickstarter) is well sealed. If not, a long hard ride can introduce some intresting flareup on your pant leg when it decides to backfire with the cool air rushing in between exhaust pulses.


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