White hot! see vid

My bike runs like this you tube clip .

I put the clip up as i can see that most posts get the responce "they all get hot and go red"
The clip shows how hot it gets which is way too hot.

I have a RMZ250 2005 with a dep exhaust.
To try and remove airleaks on the exhaust side I have fitted a new copper exhaust ring at the manifold,
and the link pipe to muffler is a push fit but to make sure it's tight i have fitted a high temp exhaust sealant.

I checked the jets installed and they are 178 main jet and 45 pilot jet the fuel screw is 2.5 turns out (the numbers are hard to read so I could be wrong)
The factory standard is 172 mian jet  40 pilot jet  and 1 3/4 turns on the pilot screw.

The bike starts after a few kicks from cold with the choke on.

If I blip the throttle and let it idle, it idles nicely.
Whilst idling I watch the header and it starts to heat up and glow.

From other posts people have said if you pull the choke out it will add more fuel and the glow should reduce.

With mine it revs harder and glows redder!!

can anyone give me something to try?

Did you know, if you let it idle long enough, it will overheat?


You have a thinwall header, it transfers heat very well. It depends on the passing air to cool it.


Soultion? Do not let the bike just sit there and idle. It is a race bike and that is bad for it.


Your choke adds fuel AND air, so the engine runs faster, burns NORE fuel, making MORE heat and over heating your bike that much faster.


If it really bothers you, put on a stock header.

If it runs better with choke on even after warm, that would indicate a lean idle mixture to me. Did you change the jetting after the exhaust install? If the exhaust flows better, you probably need to at least turn out the fuel screw a bit and possibly raise the needle and/or change the main. I'm not real familiar with DEP exhaust, but if it was a full system then it should require a jetting change. (If it didn't require a jetting change then it probably didn't do anything for performance).

The do get hot very quickly, so I wouldn't use idling in the garage as a good test environment. Jet to make it respond appropriately to choke and throttle, not to change how the header looks when you run it in the garage.

ok thanks for the responce,  so your saying just get on and ride?

I went to a motorcross event (to watch) and none of the bikes seemed to heat up like mine.

I think the glowing looks cool, I was worried i'd do alot of damage to the engine if it is running too lean.

I did not relise the choke added air as well as fuel. I thought it was just fuel so that makes more sence.

Just did a quick search and actually that doesn't make sense a "choke" got it's name because it chokes the air supply to increase the fuel ratio?

Most choke systems will add fuel to the engine to richen the mixture so William1 this can't be right?

'Choke' is now just a generic term.It is also technically a cold start knob.


Chokes used to be a butterfly valve at the entrance to the carb the cut off air. Engine vacuum was only able to pull a tiny bit of air and a lot of fuel.


Your choke knob is an enricher. It adds fuel and tiny bit of extra air. This gives you the rich mix needed on cold start and it increases idle speed.


On FI bikes, the cold start knob only adds air.It also signals the ECU to tell the injector to add more fuel.

Ok thanks for clearing that up.

Not sure if this changes the diagnosis but when you ride, it backfires on decel as well.

Not sure if this changes the diagnosis but when you ride, it backfires on decel as well.


Then your jetting is off.

Have you even tried adjusting the fuel screw?

Decel popping, assuming you have no air leaks anywhere, is a sign of a lean pilot jet circuit.

You need to properly adjust your fuel screw following William's procedure at the top of the forum.

Krannie you were spot on. I turned the idle jet screw out and you could see the colour change in the exhaust.

Becoming less red with each small adjustment.

The backfiring is gone under normal ridin, really aggressive throttle followed by a quick shut of the

throttle will give a pop but this seems fine.

It now idles in the garage and does not get red.

My advice to anyone with the same exhaust problem, if it's this red don't ride it as your bike is lean.

This super hot exhaust is a sign of a problem it's not normal.

I may need to go up a jet size, but it runs sweet for now.

Thanks for the help.

Edited by 22kilburn

............................ touch. it. :thumbsup:

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