Planet Minis

bruce bruce · 10-29-2009, 08:49 AM

I've got a e-start GPX 90cc engine in my kid's TRX90 and I'm suddenly having jetting issues. Motor came with Fake Mikuni 22 with a 100 main and a 15 pilot. I increased the pilot to a 20 and it ran great all summer (a little fat with the 20). Now the thing is cold blooded and will barely come of of idle. Cleaned the carb and verified there weren't any vac leaks. I have the air screw way out just to make it rideable. Are the fake Mikunis junk? Any recommendations for jetting? Thanks, Bruce.

tcr0148 · 10-29-2009, 01:06 PM

try adjusting the needle clip and start with and the air screw 1 turn out.

mexicanyella · 10-30-2009, 03:47 AM

Do the air screw first; you don't want to adjust two parameters at once or you won't know what the hell is going on. Air screw: in=richer, out=leaner. If you're sure you don't have an intake air leak, I'd say screw it in as far as you need to to get a good idle and off-idle transition. If you end up with a setting like 1/2-3/4 turn out from seated, you probably didn't clean the pilot jet as well as you thought. If it was running okay but a little rich before on the 20 pilot, and nothing else has changed, you almost certainly have a dirt/water contamination problem or an air leak between the carb and head.

That pilot adjustment controls idle and just off idle. The needle controls 1/4-3/4 throttle, more or less. If it runs okay in the midrange and wide open, your needle is fine.

10-29-2009, 08:49 AM	#1 (permalink)
bruce bruce PM Newbie Join Date: Aug 2009 Location: Bakersfield, Ca. Posts: 19	GPX 90 jetting problems I've got a e-start GPX 90cc engine in my kid's TRX90 and I'm suddenly having jetting issues. Motor came with Fake Mikuni 22 with a 100 main and a 15 pilot. I increased the pilot to a 20 and it ran great all summer (a little fat with the 20). Now the thing is cold blooded and will barely come of of idle. Cleaned the carb and verified there weren't any vac leaks. I have the air screw way out just to make it rideable. Are the fake Mikunis junk? Any recommendations for jetting? Thanks, Bruce.

10-29-2009, 01:06 PM	#2 (permalink)
tcr0148 1st Gear Member Join Date: Jan 2006 Location: Houston, tx lafayette, la every other wknd Posts: 243	Re: GPX 90 jetting problems try adjusting the needle clip and start with and the air screw 1 turn out.

10-30-2009, 03:47 AM	#3 (permalink)
mexicanyella El rey de los puntos Join Date: Aug 2008 Location: Troy, MO Posts: 987	Re: GPX 90 jetting problems Do the air screw first; you don't want to adjust two parameters at once or you won't know what the hell is going on. Air screw: in=richer, out=leaner. If you're sure you don't have an intake air leak, I'd say screw it in as far as you need to to get a good idle and off-idle transition. If you end up with a setting like 1/2-3/4 turn out from seated, you probably didn't clean the pilot jet as well as you thought. If it was running okay but a little rich before on the 20 pilot, and nothing else has changed, you almost certainly have a dirt/water contamination problem or an air leak between the carb and head. That pilot adjustment controls idle and just off idle. The needle controls 1/4-3/4 throttle, more or less. If it runs okay in the midrange and wide open, your needle is fine.

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