carb jet & needle position

miatawnt2b · 01-11-2021, 06:49 PM

I'm having a bog issue when I punch WOT on my 110cc atv's. I drilled out the adjustment plug from the fuel screw and tuned the stock carb best I could. The stock carb does not have an adjustable main jet needle. So I bought a PZ20 to play with. This does have an adjustable main needle, however the main and low speed jets do not have numbers on them. So I really have no starting point yet.

I have tried moving the main needle snap ring position around, but still get a terrible bog when I punch the throttle.

Does anyone have a baseline for a 110cc? What main/pilot jet size and needle position? Or am I pretty much stuck with the bog?

The engine does run quite well, even throughout the full throttle range, but I need to slowly squeeze the throttle open to WOT. After it's there, it will rip.

-J

dirtbkr188 · 01-11-2021, 08:07 PM

The off-idle hesitation is usually a lean condition, and turning the air screw IN (if it is an air screw and not a fuel screw) to richen the mixture is a step in the right direction. However, without having pilot jet numbers, it's hard to go up to the next size and reset the air screw to a baseline setting to work from.

dirtbkr188 · 01-11-2021, 08:10 PM

If you don't mind, post up a few pics of the carb you're using, so we can see what you're working with. There are a few different sytle carbs that are labeled as being a PZ20.

miatawnt2b · 01-11-2021, 08:13 PM

This is the one I bought from amazon

PZ20 Carb

-J

dirtbkr188 · 01-11-2021, 09:03 PM

This carb comes with replacement jets that are numbered, and may fit the carb you have.

The pilot jets are here and the main jets are here.

dirtbkr188 · 01-12-2021, 01:28 PM

Are you using the stock airbox or a foam pod filter with the PZ20, or the screen door air filter that came with the carb?

miatawnt2b · 01-14-2021, 09:54 PM

I got a main jet assortment today from 70 to 92. I decided to crack open the stock carb that was replaced by the PZ20 that I bought a few days ago. I had already drilled out the plugs covering the mixture screw on all three. just had to slot the bowl screws with a dremel and they came right out. I was even able to reuse them.

The main jet in the stock carb on my TaoTao 125d (110cc engine) is a 65.

Since I have 3 identical machines I am able to experiment. So I stuck an 88 in one, a 90 in another and a 92 in the third. I went so high, because my old eyes initially told me the stock jet was an 85, but after comparing them to the others, it's definitely smaller than the 70 that I have, and upon closer inspection, the stock jet is indeed stamped 65. (the 6 looks a lot like an 8).

Anyhow, the pilot jet was unchanged, I can get it to idle really good with the stock pilot jet. So I started tuning the carbs with the 88, 90, & 92 jets. I had to richen the mixture screw just a bit and increase the idle screw slightly to compensate. The one with the 92 jet in it screams. I'm a little shocked that much of an increase in jet size was possible. I'm thinking they have these things leaned WAY out from factory.

I will leave it like this a day or two and pull the spark plugs in all 3 and compare to see if i'm running too rich. I was hammering on them pretty good, and I didn't get any backfires upon off-throttle so it's likely fine. I'm using cheapo cone style filters with a nylon sock soaked in filter oil overtop. It's able to breathe much better than that junk stock filter.

01-11-2021, 06:49 PM	#1
miatawnt2b Join Date: Dec 2020 Posts: 78	carb jet & needle position I'm having a bog issue when I punch WOT on my 110cc atv's. I drilled out the adjustment plug from the fuel screw and tuned the stock carb best I could. The stock carb does not have an adjustable main jet needle. So I bought a PZ20 to play with. This does have an adjustable main needle, however the main and low speed jets do not have numbers on them. So I really have no starting point yet. I have tried moving the main needle snap ring position around, but still get a terrible bog when I punch the throttle. Does anyone have a baseline for a 110cc? What main/pilot jet size and needle position? Or am I pretty much stuck with the bog? The engine does run quite well, even throughout the full throttle range, but I need to slowly squeeze the throttle open to WOT. After it's there, it will rip. -J
	0

01-11-2021, 08:07 PM	#2
dirtbkr188 Join Date: Aug 2009 Posts: 563	The off-idle hesitation is usually a lean condition, and turning the air screw IN (if it is an air screw and not a fuel screw) to richen the mixture is a step in the right direction. However, without having pilot jet numbers, it's hard to go up to the next size and reset the air screw to a baseline setting to work from.
	0

01-11-2021, 08:10 PM	#3
dirtbkr188 Join Date: Aug 2009 Posts: 563	If you don't mind, post up a few pics of the carb you're using, so we can see what you're working with. There are a few different sytle carbs that are labeled as being a PZ20.
	0

01-11-2021, 08:13 PM	#4
miatawnt2b Join Date: Dec 2020 Posts: 78	This is the one I bought from amazon PZ20 Carb -J
	0

01-11-2021, 09:03 PM	#5
dirtbkr188 Join Date: Aug 2009 Posts: 563	This carb comes with replacement jets that are numbered, and may fit the carb you have. The pilot jets are here and the main jets are here.
	1

01-12-2021, 01:28 PM	#6
dirtbkr188 Join Date: Aug 2009 Posts: 563	Are you using the stock airbox or a foam pod filter with the PZ20, or the screen door air filter that came with the carb?
	0

01-14-2021, 09:54 PM	#7
miatawnt2b Join Date: Dec 2020 Posts: 78	I got a main jet assortment today from 70 to 92. I decided to crack open the stock carb that was replaced by the PZ20 that I bought a few days ago. I had already drilled out the plugs covering the mixture screw on all three. just had to slot the bowl screws with a dremel and they came right out. I was even able to reuse them. The main jet in the stock carb on my TaoTao 125d (110cc engine) is a 65. Since I have 3 identical machines I am able to experiment. So I stuck an 88 in one, a 90 in another and a 92 in the third. I went so high, because my old eyes initially told me the stock jet was an 85, but after comparing them to the others, it's definitely smaller than the 70 that I have, and upon closer inspection, the stock jet is indeed stamped 65. (the 6 looks a lot like an 8). Anyhow, the pilot jet was unchanged, I can get it to idle really good with the stock pilot jet. So I started tuning the carbs with the 88, 90, & 92 jets. I had to richen the mixture screw just a bit and increase the idle screw slightly to compensate. The one with the 92 jet in it screams. I'm a little shocked that much of an increase in jet size was possible. I'm thinking they have these things leaned WAY out from factory. I will leave it like this a day or two and pull the spark plugs in all 3 and compare to see if i'm running too rich. I was hammering on them pretty good, and I didn't get any backfires upon off-throttle so it's likely fine. I'm using cheapo cone style filters with a nylon sock soaked in filter oil overtop. It's able to breathe much better than that junk stock filter.
	0