Carb tuning advice

chiliphil1 · 04-12-2018, 04:36 PM

Hello, I just recieved my order from power sports max today, I have 2 new carburetors to install! They are both x-pro 19mm carbs. I am installing them on 2 110cc atv's, one is a coolster, the other is a Kazumi. I am going to toss these on this weekend, I am just wondering what a good starting point it for the screws? I know I will have to tune them a bit but as far as firing up and idling where should I set them?

Thank you.

dirtbkr188 · 04-12-2018, 04:48 PM

A baseline for the air or fuel screw is usually 1.5 to 1.75 turns OUT from seated, giving you 1.25 to 1.5 turns on either side, for starters. Setting the jet needle clip in the 3rd notch from the top gives you two notches on either side, to richen or lean it.

chiliphil1 · 04-12-2018, 10:14 PM

Quote:

Originally Posted by dirtbkr188

A baseline for the air or fuel screw is usually 1.5 to 1.75 turns OUT from seated, giving you 1.25 to 1.5 turns on either side, for starters. Setting the jet needle clip in the 3rd notch from the top gives you two notches on either side, to richen or lean it.

Thank you very much sir, that’s exactly what I was looking for!

chiliphil1 · 04-13-2018, 06:19 PM

Quick question, I installed the carbs and adjusted as advised. The 2 units are doing different things now. The smaller one which is a coolster 110 mini atv would idle with the new carb but would bog and die when revved. I kept the new slow jet in and out the old main jet in the new carb, now it idles but a little too high, it will roll when sitting at idle, it’s too high for the centrifugal clutch to hold it, it also bogs when riding, if you are going along it will run smooth and then start to sputter, clear out and run fine, sputter, repeat. For some reason the adjustment screws on the carb seem to have no effect on anything.

The bigger one which is a kazumi 110 runs and rides well, the idle is good and the adjustments work. The issue it’s having is that when you rev it it will rev up very high and then come back down. If you blip the throttle it’ll rev up, even if your finger is off of the throttle before it comes back down to idle. I cannot figure out why it’s doing this. Adjusting the screws seems to do nothing for this issue.

Any help here is greatly appreciated.

Douglass · 04-13-2018, 07:15 PM

This is my understanding of the functions. Your pilot jet and air fuel screw are going to control fueling from idle to about 1/4 throttle. The Needle clip is going to fine tune from 1/4 to 3/4 throttle, and the main jet will control WOT.

With my 2017 Coolster 125cc atv I installed a carb off of amazon. My idle quality/consistency improved 100% from the stock carb. With the new carb if I do a WOT from idle it will bog and die if I don't let off. When playing with the needle clip positions, I placed the clip at the lowest position (rich), and the bog went away. After doing this I was now having sputtering and bucking (to rich) with light throttle. I'm sure the main jet is to small, and I would be bet that if the main jet was increased in size I would be good through all throttle positions. I have not addressed this yet, as my five year old drives the atv, and I have it limited to about 15mph (very little throttle). With the clip in the #3 (middle) it gives him excellent drive ability.

With the aftermarket carb in the current setting I can get very aggressive with the throttle, but just not from idle. From idle it needs to be progressive, but once I'm going I can lay all the way into it. Once my son's skills improve, I'll deal with the main jet.

Hope this helps

04-12-2018, 04:36 PM	#1
chiliphil1 Join Date: Apr 2018 Posts: 15	Carb tuning advice Hello, I just recieved my order from power sports max today, I have 2 new carburetors to install! They are both x-pro 19mm carbs. I am installing them on 2 110cc atv's, one is a coolster, the other is a Kazumi. I am going to toss these on this weekend, I am just wondering what a good starting point it for the screws? I know I will have to tune them a bit but as far as firing up and idling where should I set them? Thank you. __________________ Apollo DB99 125, SSR 110, Kazumi 110 atv, Coolster 110 atv, BMW R nine T pure.
	0

04-13-2018, 06:19 PM	#4
chiliphil1 Join Date: Apr 2018 Posts: 15	Quick question, I installed the carbs and adjusted as advised. The 2 units are doing different things now. The smaller one which is a coolster 110 mini atv would idle with the new carb but would bog and die when revved. I kept the new slow jet in and out the old main jet in the new carb, now it idles but a little too high, it will roll when sitting at idle, it’s too high for the centrifugal clutch to hold it, it also bogs when riding, if you are going along it will run smooth and then start to sputter, clear out and run fine, sputter, repeat. For some reason the adjustment screws on the carb seem to have no effect on anything. The bigger one which is a kazumi 110 runs and rides well, the idle is good and the adjustments work. The issue it’s having is that when you rev it it will rev up very high and then come back down. If you blip the throttle it’ll rev up, even if your finger is off of the throttle before it comes back down to idle. I cannot figure out why it’s doing this. Adjusting the screws seems to do nothing for this issue. Any help here is greatly appreciated. __________________ Apollo DB99 125, SSR 110, Kazumi 110 atv, Coolster 110 atv, BMW R nine T pure.
	0

04-12-2018, 04:48 PM	#2
dirtbkr188 Join Date: Aug 2009 Posts: 507	A baseline for the air or fuel screw is usually 1.5 to 1.75 turns OUT from seated, giving you 1.25 to 1.5 turns on either side, for starters. Setting the jet needle clip in the 3rd notch from the top gives you two notches on either side, to richen or lean it.
	1

04-13-2018, 07:15 PM	#5
Douglass Join Date: Aug 2017 Location: Bay Area, CA Posts: 375	This is my understanding of the functions. Your pilot jet and air fuel screw are going to control fueling from idle to about 1/4 throttle. The Needle clip is going to fine tune from 1/4 to 3/4 throttle, and the main jet will control WOT. With my 2017 Coolster 125cc atv I installed a carb off of amazon. My idle quality/consistency improved 100% from the stock carb. With the new carb if I do a WOT from idle it will bog and die if I don't let off. When playing with the needle clip positions, I placed the clip at the lowest position (rich), and the bog went away. After doing this I was now having sputtering and bucking (to rich) with light throttle. I'm sure the main jet is to small, and I would be bet that if the main jet was increased in size I would be good through all throttle positions. I have not addressed this yet, as my five year old drives the atv, and I have it limited to about 15mph (very little throttle). With the clip in the #3 (middle) it gives him excellent drive ability. With the aftermarket carb in the current setting I can get very aggressive with the throttle, but just not from idle. From idle it needs to be progressive, but once I'm going I can lay all the way into it. Once my son's skills improve, I'll deal with the main jet. Hope this helps
	1