Hot Tail Pipe

Hello,

I just did the Throttle screw mod and gray wire mod, that's it. Everything else is stock. 2009' WR450F. Hell of a time starting it...then after running it for a about 10 minutes I shut it down and noticed the tailpipe was hot as hell! Is this normal?

Hard starting will not be realted to the gray wire or stop. You must of doene something else or the bike has been sitting a long time and the fuel is old.

Was it ten minutes sitting still in the garage, 10 minutes putting about the yard or 10 minutes WFO? The first and last modie will def. get the pipe blazing.

I bought the bike last week, brand spanking new...the bike sat in my unheated garage until yesterday. I hadn't even started it. I then did the gray wire mod, then onto the throttle stop change out. I put everything back together and tried to start it...no go. I put the bike on the charger, then tried some more. I finally got it to run with the kick start...didn't idle worth a darn! I suspect it's the cold blooded nature(not starting with out a good fight on a cold day, 19 degree's). Once I had it running, I rode it around the block in gears 1st-3rd, for about 10 minutes. Then I shut it down and parked it back in the garage. A few minutes go by and I had noticed the header pipe was luke warm, but the silencer was freakin' hot to touch! Normal?

Thanks a bunch...I know the hot tail pipe thing has lingered in this forum a few times already...I just worry about running the bike too lean and having valve trouble, engine problems early on! I'm a worry wart!

P.S.

Bike brand new. Gray wire and throttle stop mod, are the only mods done on bike. Should I worry about jetting right now, or can I run the bike as is without a problem?

Jarrod

.

A few minutes go by and I had noticed the header pipe was luke warm, but the silencer was freakin' hot to touch! Normal?

Weird.

The only possible explanation I can give is that maybe the fact that the header is made from a single layer of thin metal plate it dissipates heat quickly, but the muffler has multi-layers (ok, only three!) of metal and silencer packing (fibreglass?) that work together to retain heat.

I've never checked mine ('08 WR450F) after a few minutes of stopping the engine.

Might give it a try next time if I remember.

Greg

+2 on Greg's comment. The Packing in the muffler holds the heat too. All normal.

You bike is not jetting for those temps. You need a much larger starter jet. Then you'll have to adjust the fuel screw once the bike is heated up from riding.

BTW, you cannot jet a 4S so lean as to cause damage. Even if you make it so lean as to barely run, it will not get hurt.

+2 on Greg's comment. The Packing in the muffler holds the heat too. All normal.

You bike is not jetting for those temps. You need a much larger starter jet. Then you'll have to adjust the fuel screw once the bike is heated up from riding.

BTW, you cannot jet a 4S so lean as to cause damage. Even if you make it so lean as to barely run, it will not get hurt.

Wait... you can't jet lean enough to hurt anything? Is that because in theory it won't run if you get it lean enought to hurt something?

oh... and +1 on the jetting. Arent they jetted for around 70 degrees at sea level... something I heard once

as for exhaust, Oh yeah its going to get hot, especially if its running lean and all the stuff in the silencer is going to hold heat better than the header... mine is the same way (header cools quicker that its)

A 4S does not depend on the carb to deliver oil like a 2S. All that will happen is the engine will get a 'dry' bog and as you lean it further, will not run. Not a therory, it is a fact.

Bikes are jetted for 65 degrees, 50% humidity, 30 inches of air pressure. It is air densiy that matters. But you cannot and never should assume that the stock jetting is bad (or perfect). It should instead be considered a valid starting point to begin the jetting process.

Ok...before the snow melts I will probably have re-jetted the carb and removed snorkel and baffle. I have three months to stare at the bike in the garage until the white stuff goes away. Thanks for all the great information! Always fun talking shop!

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