I've got a 300 2 stroke Polaris that I've just installed a 34mm carb with a UFO on it instead of the stock 30mm carb.I am going to install an EGT guage to help with the jetting. I need to know what temps I should look for and at what throttle positions. I know the a WOT I don't want to go over 1250 but does this also apply for 1/4 throttle and 1/2 throttle?Please reply!!! I already posted this in the Polaris forum and didnt get any responses at all. I guess if I'd asked "whats faster a 500 or 700 sportsman" I would have had a hundred responses!!!

 

I read on dirtwheels that the most a two stroke motor can take is 1350, well actually if you hit that your piston is gone. I am guessing at full throttle in any gear is shouldnt go passed 1300.
I would also suggest to get a head temperature gauge, that could help also. I am installing my egt as soon as possible cuz I blew my motor this passed weekend. Try www.pro-flow.com , they have some good 2 stroke guages and probes.
Peace

 

I shoot for 1250, but don't worry about it unless it starts hitting 1300. The thing is that the EGT readings are affected by probe placement, timing, etc. My FL350 motor is rev ported so the exhaust exits the cylinder sooner transfering less heat to the cylinder. I run my Drakart at lower EGT readings. You need to get your jetting right and then note what temps it runs at. You can then jet at the edge knowing that you'll see a change in the guage if conditions change like a drop in ambient air temperature.

The best thing to do would be to put the stock carb back on and install the EGT. Stock jetting was probably rich so you could jet it down. Note the temps and then install the bigger carb. Shoot for the temps you got with the stock carb. Double check your numbers by checking your jetting in other ways.

I jet low end for good idle and throttle response. The EGT readings I get are different on different machines. I see recomendations for jetting mid throttle the same as WOT. That is fine, but I jet on the rich side. I figure that if I want maximum power, I'll be at WOT. Since I don't need max power, I might as well be safer. Also, when I ease off the throttle from a long WOT run, the extra fuel will cool it off.

 

I have used egt's on snowmobiles and I had a hard time reading them because your bouncing around so much that you can't see the gauge. I recommend putting a small piece of red tape at your danger point so that you can see it. The time between actually running too hot, and meltdown is very short! I also had jetted too rich once and the gauge read really hot, I was told this was because of afterburn? I think(i'm no expert). If you have trouble and want to now if your rich or lean, I just look at the piston wash. Good luck.

 

The digital guages are a bit easier to read. At least in terms of knowing when you at the limit. The guage on my Drakart is an analog one with dual needles. 1200 is about when the needles are inline with each other so it is pretty easy to read.

Piston wash is a good way to get baseline temps for the EGT. Once it is jetted right and you know what your numbers should be, then the guage will tell you when there is a problem.

I can tell by engine feel what needs to be done if it is one or two sizes off. When I make a change like a pipe or intake, I used to be really conservative. Jet way up and drop down one size at a time after extensive testing. I am paranoid at times. With the EGT reading 1000, I'll drop two jet sizes without worry. I save a lot of spark plugs now.

 

I guess what I'll do is jet it rich and start leaning it out to where it is safe. I also had a guage on my Formula Plus sled last winter and it was hard to read because or vibration. What I did was took a piece of black tape and put it on the guage lining up with the 1250 mark. I then trimmed around the edge of the glass so basically if the needle disappeared I was above the 1250 mark.Also I would like to check the jetting by the "piston wash method" but this is also a lot easier on a sled than a bike that has the plug jammed up under the gas tank.I would have to remove the gas tank each time to check it.Also one other thing this 300 is very sensitive to jetting lean cause it will detonate very easily if jetted just a bit too lean. I found this out after installing the UFO and dropping the pilot down from a 35 to a 17.5. It would rattle like hell whan cruising a 1/8 throttle even though it seemed to be running rich enough at idle.Turning in the air screw wouldn't even stop it.I went up to a 20 and the rattle is gone.But these UFO's are another story in themselves.They might stay and they might go.I will decide when my RCR pipe gets here in a couple of weeks.