2 stroke jetting pain

May 7, 2003

I ride 4 strokes, but just recently bought a 2000 RM125 for a second bike for my wife to ride.

I am having are hard time getting the jetting dailed in. When I first got it is was running SUPER rich. The rear fender would have oil spewed all over it when I would start it up.

The bike has a procircut pipe with a 304 silencer on it. I don't know how that affects jetting? I must admit I am not as good at tuning 2 strokes as I am 4 strokes.

Anyway, I ride pretty much at sea level. The current temp here in Canada where I live is in the high 30's to mid 40's F or 3 - 12 degrees celcius.

I am running 34:1 fuel mixture.
The stock jetting is 50 pilot jet, 4 clip on the needle, and a 175 main. This is too rich even at the colder temps.

With an aftermarket pipe, how do I move the jetting?

PLEASE help. My wife is fouling plugs left and right and she is not afraid to rev it, but if there is any slow riding the plugs foul pretty fast.

should I try to lean out the mixture? If anyone is familiar with this year and model advice is more than welcome.


Last edited by a moderator:
Oct 30, 2003
Just to point out I think those specs specify race gas.
Anyways take jetting specs with a grain of salt. You can use them as a starting point but to set your bike by them isnt the best plan. There are too many variables like temp, gas, oil ratio, etc etc. Have a go at those links and jet it up