Yz 250 egt

I got my 2005 YZ 250 top end together after two failures within a few rides (piston damage exhaust side from heat). I have checked everything I could think of that may be a culpret. I found a clogged pilot jet, fairly low float setting. In addition, for piece of mind I replaced the seal behind the flywheel, repacked the silencer, richened the jets a step or two, retarded the timming to .005" BTDC, and am running race gas mixed 1 : 3 with pump gas. I am going to spend some time jetting this week.

I have a IR temp gun, I was thinking of taking it with me for a few rides to check the temp of the exhaust pipe at the cylinder when I pull up to the truck. I don't have in mind to use this temp for tunning, but just detect a problem I may have missed that is causeing high pistion temps.

My question is -Does anybody know what a normal temp would be and how high of a temp would indicate there is a problem (lean, detenation, or timming)?


Not with an IR gun...and it would have to be during WOT under load to be meaningful.

There is no way to accurately guess from the outside of the pipe. A pyro or afr is pretty much your answer.

You are obviously lean....you fixed that....right?

Have you checked your spark plug color after a WOT, under load situation? Get your bike on the pipe in 3rd gear, then immediately shut it off. Check the plug color. This is the way that 99% of people in the world check their jetting. Start out very RICH if you are unsure.

Check this link:


It should help you out a lot.

I'm not sure of your location, but if you are way above the recommended jet settings, you could have an air leak. Check your coolant! Check for coolant flow! Since you are re-building your own bikes, i'm sure that you can spot a cylinder with bad plating.

Isolate and you will find your problem!

Oh and FYI on using egt to judge jetting:

Ideal jetting (most power) causes the EGT to be at its highest point. Anything richer and the temp goes down. Anything on the lean side, the temp goes down. Think of a bell curve.

Of course we all want to be a tad on the rich side of this for longevity.

A good egt for a two stroke race kart engine is roughly 1k degrees f. It is much more practical to use your spark plug color.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now