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Dusman · 03-29-2020, 09:39 AM

I wanted to post a final update here on the Coolster 125cc Pitbike.

With the extensive help from dirtbkr188, I adjusted the Xjoy carburetor (a Molkt PZ22 Keihin/Mikuni mix clone) up one side and down the other and just never could get it to run correctly. I purchased a genuine Mikuni back in October, but really wanted to try to get this cheaper carb to run right for the purposes of getting a better carburetor education.

However, after cleaning, rebuilding, rejetting the Molkt every which way but loose, and trying just about everything, I simply couldn't get it to run right after hours of working on it.

Yesterday, after working on it for a few more hours, I took a break, got some lunch, and said, "I've worked enough with this clone; I'm putting the Mikuni on."

The Mikuni came factory jetted at a 95 main and 15 pilot, which should have been about right for our elevation.

I put her on, gave the bowl time to fill up, and she fired up on the first kick. The idle was *ridiculously* high, so I turned the idle screw out and it still didn't seem to want to idle at a proper rate. I took the Mikuni off and made sure that the jets were seated properly, the needle wasn't floating around, and that there wasn't something I overlooked, such as a vacuum leak at the intake manifold or the pod filter. I tightened everything back down, fiddled with the idle screw a bit more (it's a weird one, never seen anything like it), and finally she started to settle down.

She runs like a top now and will get up to @ 42 mph (GPS confirmed). No bogging, no hesitating once she's warmed up, and she truly runs like a champ with that Mikuni on. I'm not exaggerating when I say this, but if you buy a Coolster 125cc pit bike and you're having bogging issues, I'd recommend just going ahead and purchasing a PZ22 Mikuni or getting this kit from t-boltusa.com:

https://tboltusa.com/store/mikuni-22...nis-p-107.html

Below are a few videos of the information and some seat-time action. In these videos, I put them together to update dirtbkr188, who has been a *tremendous* help through these last 6 months. That dude has given me a "college education" on carb tuning! Seek him out if you are serious about tuning your bike. He is a huge help and enjoys teaching other folks how to do this:

03-29-2020, 09:39 AM	#39
Dusman Join Date: Jan 2018 Location: NC Posts: 217	Finally...Mikuni PZ22 success! I wanted to post a final update here on the Coolster 125cc Pitbike. With the extensive help from dirtbkr188, I adjusted the Xjoy carburetor (a Molkt PZ22 Keihin/Mikuni mix clone) up one side and down the other and just never could get it to run correctly. I purchased a genuine Mikuni back in October, but really wanted to try to get this cheaper carb to run right for the purposes of getting a better carburetor education. However, after cleaning, rebuilding, rejetting the Molkt every which way but loose, and trying just about everything, I simply couldn't get it to run right after hours of working on it. Yesterday, after working on it for a few more hours, I took a break, got some lunch, and said, "I've worked enough with this clone; I'm putting the Mikuni on." The Mikuni came factory jetted at a 95 main and 15 pilot, which should have been about right for our elevation. I put her on, gave the bowl time to fill up, and she fired up on the first kick. The idle was ridiculously high, so I turned the idle screw out and it still didn't seem to want to idle at a proper rate. I took the Mikuni off and made sure that the jets were seated properly, the needle wasn't floating around, and that there wasn't something I overlooked, such as a vacuum leak at the intake manifold or the pod filter. I tightened everything back down, fiddled with the idle screw a bit more (it's a weird one, never seen anything like it), and finally she started to settle down. She runs like a top now and will get up to @ 42 mph (GPS confirmed). No bogging, no hesitating once she's warmed up, and she truly runs like a champ with that Mikuni on. I'm not exaggerating when I say this, but if you buy a Coolster 125cc pit bike and you're having bogging issues, I'd recommend just going ahead and purchasing a PZ22 Mikuni or getting this kit from t-boltusa.com: https://tboltusa.com/store/mikuni-22...nis-p-107.html Below are a few videos of the information and some seat-time action. In these videos, I put them together to update dirtbkr188, who has been a tremendous help through these last 6 months. That dude has given me a "college education" on carb tuning! Seek him out if you are serious about tuning your bike. He is a huge help and enjoys teaching other folks how to do this:
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