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Discussion Starter · #1 · (Edited)
Swapped to a PWK 21 Carb….
141667

i need a little help, I kinda dug myself a hole.
It’s a 2007 Raptor 80cc
New
-Top End & Jug
-Ported Intake tube, (from 19mm to 23mm)
-Ported and Polished exhaust side
-New valves, (reseated)
-PWK 21mm carb, ( stock is 17mm)
-Gutted Exhaust
-POD air filter


the bike was running very lean with new stock carb. So I saw the PWK on Amazon and within one day it was at my house. Well it didn’t come with any jets other than the ones in it.
105mm Main Jet
38mm Pilot Jet
…..I know… why would I do this???
But I’m ordering a jet kit,
What Sizes should I put in.
It bogs and almost dies when I blip the throttle and if I slowly hit the gas it starts spit’n and sputtering acting like a misfire.
Did I royally mess this up? 😂
Seriously please help it’s my little girls bike. And all she wants to do is ride. And when I’m trying to tune it, she’s right there waiting for me to tell her it’s good go ride.
141668
Tire Wheel Plant Automotive tire Tread
 

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www.jetsrus.com
find out which carb jets you need
then go with sizes from there.
Slowly add rpm until you find a problem at whatever rpm range, roughly.
Pilot jet controls idle to 1/4 throttle
Needle position controls 1/4 to 3/4
Main jet controls 3/4 wide open.
I would buy the lowest 3 sizes of pilots and mains available for whatever carburetor you are actually using.
Start with the smallest of each jet first, and only change one thing at a time.
Start with the needle at or near the center groove.
The fuel screw(flat blade screw on outside of carb body is basically a valve for the pilot jet, so you can find tune the pilot circuit with it.
I would start at 1 or 1.5 turns counter clockwise from fully right/seated.
If you turn it one full turn in either direction, it should effect performance enough for you notice, usually bad, but enough to know if you need to continue in the same direction or go back the other way, you count your way back and forth to 1/8 turns until it is dialed in(make a change, wait 10 seconds or so, give it a little throttle, let off, let it return to idle, and let it run until it settles before you move the fuel screw again, or, turn it off when you change it).
The smallest, or definately one of the next pilots will supply more than enough fuel for that engine.
The needle will likely be center, or one clip position up or down.
Having stock and the next 2 sizes up on the main jets should be more than enough also.
You are into unknown territory as to just how well that little 80 can flow, and at what point a carb is too big.
If you cannot make the engine run well with that aftermarket carb, and you have the smallest jets already in it, then you will have to try another carburetor.
I would look at stock carbs for the likes of an old Honda XR 80 or 100cc.
There were several good models of 4-stroke 80cc, 100cc, and slightly larger 1980's and 1990's dirtbikes from all the Japanese bike makers, and I'm sure one would work on your 80 with little to no modification.
I know that model 80 fourwheeler you have is ridiculously slow and choked up stock.
Don't give up yet, you may or may not need a different carb than what you have now, but you Can get that engine to run good, and alot better than stock.
 

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Discussion Starter · #3 ·
www.jetsrus.com
find out which carb jets you need
then go with sizes from there.
Slowly add rpm until you find a problem at whatever rpm range, roughly.
Pilot jet controls idle to 1/4 throttle
Needle position controls 1/4 to 3/4
Main jet controls 3/4 wide open.
I would buy the lowest 3 sizes of pilots and mains available for whatever carburetor you are actually using.
Start with the smallest of each jet first, and only change one thing at a time.
Start with the needle at or near the center groove.
The fuel screw(flat blade screw on outside of carb body is basically a valve for the pilot jet, so you can find tune the pilot circuit with it.
I would start at 1 or 1.5 turns counter clockwise from fully right/seated.
If you turn it one full turn in either direction, it should effect performance enough for you notice, usually bad, but enough to know if you need to continue in the same direction or go back the other way, you count your way back and forth to 1/8 turns until it is dialed in(make a change, wait 10 seconds or so, give it a little throttle, let off, let it return to idle, and let it run until it settles before you move the fuel screw again, or, turn it off when you change it).
The smallest, or definately one of the next pilots will supply more than enough fuel for that engine.
The needle will likely be center, or one clip position up or down.
Having stock and the next 2 sizes up on the main jets should be more than enough also.
You are into unknown territory as to just how well that little 80 can flow, and at what point a carb is too big.
If you cannot make the engine run well with that aftermarket carb, and you have the smallest jets already in it, then you will have to try another carburetor.
I would look at stock carbs for the likes of an old Honda XR 80 or 100cc.
There were several good models of 4-stroke 80cc, 100cc, and slightly larger 1980's and 1990's dirtbikes from all the Japanese bike makers, and I'm sure one would work on your 80 with little to no modification.
I know that model 80 fourwheeler you have is ridiculously slow and choked up stock.
Don't give up yet, you may or may not need a different carb than what you have now, but you Can get that engine to run good, and alot better than stock.
Sounds great. Thank you.
mThe smallest main Jet that I have found for the PWK 21mm is a “90”? I’m running a 105.
and I have seen that running a 80 main in the stock bike ( stock carburetor is 17mm) and they have seen improvement. So I’m hoping with the porting and polishing that the “90” in the PWK 21mm will fix the the top end issue. And running a larger Pilot Jet. There is a 38 I believe, I’m not sure. But I’ll move up to a 45. And see how that changes mid range.
 
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