I always ran on 240. But at the moment with the cool air. The ignition being heavily advanced and no snorkel I'm running 300 main jet. Might sort it out today though
if your carb is the standard 28mm then your bike is running really lean with a 160 main jet unless its been modded in some way but yea 240 main jet for the dtr and I think its 210 for the dtre's
you wont get any more power just off going up jet sizes you only do that if you increase the air intake upjeting to 270 to 300 will just make the engine run rich/ hotter causing damage u should down jet to 240
I have a full DEP system though, i had a 250 jet in just with standard front and big one end can. and when i put full dep on.. the was NO power. so went to 260 jet and it's alrite now. just thought would run better with bigger jet. i guess i will leave it :) also i have snorkel taken off.
__________________
''Regular maintenance is the key to reliability; irregular maintenance is the key to great exercise''
Have a read up on carburettors to fully understand them before playing around with jetting. Its really interesting and will also help you massively. The book that Cal has been mentioned "graham bell 2 stroke tuning" is very good and has a great section on carbs. The ultimate goal of a carb is to mix the air and fuel into a perfect mix that will combust in the right way when the spark ignites it at each throttle position and engine Rpm.
Increasing the main jet size will allow more fuel to be added to the air but the air quantity stays the same. More petrol in the mixture doesnt mean more power. The balance has to be just right to get optimum peformance caused by the best bang ( best mixture). Once you go passed the right amount of petrol you will just be running over rich and will lose power and waste fuel. The idea is to use the smallest size jet as possible without running lean and causing damage.
If you're bike is running nicely with a 260 jet then keep it! The power difference you'll may get from changing wont be huge and could risk your engine. That level of jetting is more for race bikes which are being stripped down constantly and rebuilt. You want your bike to run reliably and it sounds like it is.
-- Edited by AndyYam on Sunday 2nd of March 2014 02:20:49 PM
It's also quite important to mention that engine age/wear will require different jetting so I'm now gonna say that mine was 240 and was very rich. So stepped down and made a note of what I was noticing that was different, finally landed on 220, one size bigger than the original for my bike (06 DTRE). Check the Haynes manual for standard jet sizes and then do some thorough reading on what needs to be done.
