So my girlfriend has a YZ125 that I've been working on getting jetted properly because back when she started riding with me a few months ago, it was running so rich it'd cover the swingarm in goo and foul a plug in about an hour. Granted, she's a little timid on the bike. (obviously not the best choice in bike for her to buy, but she got it before I met her) But, I also know from experience from riding my Gas Gas 200 that if a 2 stroke is jetted right, you can bog it without fouling. So, I read the big awesome sticky about jetting 2 strokes, but I have a gremlin remaining.

I got the pilot tuned in, but then ran into trouble with the needle. The way it was set up, it was lean on the top end of the needle's responsibility, so I lowered the clip (down one notch from where it had been, to the last notch) and fixed that problem, and then moved on to get the main set right. But, after all was said and done, a problem that had been there before in the performance was still there. The bike runs pretty rough with small throttle openings. Doesn't matter what RPM you're at, it's pretty sputtery if you open the throttle less than half. Full throttle is awesome. Doesn't change whether the bike's warm or cold.

So, do I need a new needle, or am I still too rich on my pilot circuit? Since I don't have the bike right here with me now, I can't look at which needle it has, and I'm not looking for y'all to tell me exactly what I need, I'd like to think I'm smart enough to figure that out, I'm just wondering generally what y'all think needs to be changed, and in what direction. As in if I need a new needle, what am I generally looking for. (ie longer, fatter, etc...)

FWIW, I'll give my conditions:

99 YZ125
4200' elevation, temps around 50-60 this time of year
FMF fatty pipe, FMF powercore silencer
Down to a 330 main and 45 pilot

Thanks!

Many people mistake carburation or jetting problems with needing a new top end.
I see this every day.
When I tell people this I usually hear, "We just put a new piston and rings in it".
Sometimes you can put a new piston and ring in a bike and it's fine.
If your bike is more than a few years old a piston and ring job is not usually enough.
A cylinder can look great and even pass a quick mic job.
However, unless you have experience with a mic and unless you have a decent set of mics that are properly calibrated you are better off letting someone mic your cylinder who has the proper experience.
A measurement of .0005 (4-6 times smaller than a hair off your head) or less can be the difference it a cylinder that can seal with a new set of rings and one that wont.
If your cylinder does not pass a careful inspection, then it will need to be repaired and re-plated or sleeved.
Once your top end is correctly repaired, do a compression check.
If it does read at or better then factory specs, no amount of jetting will help, really.
Also, be sure your reeds and exhaust valve assembly are clean and in good repair.
Last but not least, check your Carburetor boot to be sure there is no cracks.
Moto

Many people mistake carburation or jetting problems with needing a new top end.
I see this every day.
When I tell people this I usually hear, "We just put a new piston and rings in it".
Sometimes you can put a new piston and ring in a bike and it's fine.
If your bike is more than a few years old a piston and ring job is not usually enough.
A cylinder can look great and even pass a quick mic job.
However, unless you have experience with a mic and unless you have a decent set of mics that are properly calibrated you are better off letting someone mic your cylinder who has the proper experience.
A measurement of .0005 (4-6 times smaller than a hair off your head) or less can be the difference it a cylinder that can seal with a new set of rings and one that wont.
If your cylinder does not pass a careful inspection, then it will need to be repaired and re-plated or sleeved.
Once your top end is correctly repaired, do a compression check.
If it does read at or better then factory specs, no amount of jetting will help, really.
Also, be sure your reeds and exhaust valve assembly are clean and in good repair.
Last but not least, check your Carburetor boot to be sure there is no cracks.
Moto