Help! Need advice on tuning a Mukuni 22 Carb on a Stock Predator 212cc non-Hemi

#1
Engine keeps cutting out when I give it throttle esp full throttle. It will idle just fine...and sometimes if i'm slow with the throttle it will get up to speed (sometimes). Any suggestions would be helpful.
 
#3
Can you be more specific on changing the main jet? I bought a MIKUNI 22 carb for my Predator 212, that i had mounted on a Harley Pocketbike that was bought as a rolling frame without no engine, and that MIKUNI carb dont want to idle either unless the idle screw is turned all the way in to the right,full stop. Ive seen one or two Predator 212 YouTube videos mentioning replacing the factory carb jet with a better quality one, but i need more details on where to buy that better quality needle jet, and which size jet will be used
 
#6
Just to be clear, is this happening when cracking the throttle wide open off idle? When you slowly get it up to speed how does it run at full throttle?
 
#7
A stumble or bog can is most likely caused by the needle position. There are 5 grooves for the E clip to fit in.
Moving the clip down (toward the pointy end of needle) will richen the circuit.
As the throttle is advanced, the needle is lifted out of the needle jet allowing more fuel to enter the engine.
Try moving the E clip one position down and test drive it.
If it is a brand new carb is could and probably does have some crap in the carb. Take the carb all apart and spray carb cleaner through every hole and clean every part thoroughly. The idle jet could be plugged too causing a lean stumble off idle.
You can search YouTube for Mikuni videos and see how to do this if you aren't familiar with it.

Danford1
 
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#8
Here is a video of a carb "like" what you probably have. You can see the needle and E clip in it.
Danford1
[video=youtube;0At4G9X29JI]https://www.youtube.com/watch?v=0At4G9X29JI[/video]
 
#9
I took the sparkplug out and it was pretty black. Im guessing its running too rich. The stock setting it came with for the E Clip was one down from the center notch. I moved the e Clip up to the middle. It still boggs down when giving it full throttle from idle...but if i throttle it up slowly it gets to full throttle. If I get that Jet Kit is there a particular size jet that works best with a stock Predator 212cc.
 
#10
Do you know what jets are in it now? When I built my clone a number of years ago I ended up with a 130main and a 15pilot (I think, it’s been a while)
 

noseoil

Active Member
#11
I did a 130 main as well, but it depends entirely on the mods you have done (cam, compression, intake, exhaust, timing, etc.). I did this with a real Mikuni (VM22-133) & it was right, but you need to tune the main jet before playing with the needle setting, or it's a waste of time in general. I ran the stock idle jet & it was fine.

Black plug & a full throttle bog sounds like it's way too rich to me. Find out what jet you have & make sure someone didn't drill it out & make it too big. 120-130 should be close on a modded motor. Get it running right before you play with the needle setting. For now just set it at the middle position as a starting point & tune the main jet.
 
#12
Only way i was able to get my Predator 212 with that MIKUNI carb to even start was to halfway open the choke and the fuss with the idle idle screw, what notch setting on that carb jetting needle does a Non-Hemi Predator use ? Because now i cant even get the engine to start and i smell gas when cranking the engine(engine is getting flooded)
 
#13
Engine efficiency, ambient temperature, humidity, and altitude have big enough effects so as to make some other guy's setting useless to you.

You really need to get yourself a couple of main jets, and keep going down in size until you start getting the throttle response you are looking for. Once you achieve that, go to the next smaller main jet. See if response improves. If it's still slightly rich, THEN move your needle clip up a notch. If it gets better, but not perfect, move it up another notch. If not, move the clip back down to where it was, and go with the next smaller main jet, and repeat.

Here is a sentence out of the link from what is probably the best description and troubleshooting guide I have found: "If the engine is having troubles at low rpm (idle to 1/4 throttle), the pilot system or slide valve is the likely problem. If the engine has problems between 1/4 and 3/4 throttle, the jet needle and needle jet (most likely the jet needle) is likely the problem. If the engine is running poorly at 3/4 to full throttle, the main jet is the likely problem."

There is a reason that needle has five grooves on it. Don't be afraid to use them.

Here is the link. I highly recommend reading all of it before proceeding.
 
#15
Did you ever get it to work? I'm having a similar problem with my 22mm Chinese Mikuni from GoPowerSports.
It's a jetting or adjustment issue. Like Havasu Dave posted, there are too many variables when it comes to jetting to just tell you that X and Y will fix the issue. Read the link he posted too.
 
#17
I just picked up a bike with a stock Predator 212 that has a Mikuni 22 carb kit on it and open pipe. It was doing the same stuff described here, bogging at higher throttle/rpm. The carb had the stock 15 pilot and 95 main jets. I found someone recommending 17.5 and 140 jets, so I ordered a set. I also found a Mikuni main jet drill chart online and in the meantime figured I'd mess with it and drilled out the stock 95 main with a #54 drill bit, which is supposed to be equivalent to a 140. Put it back together and the bike revs out cleanly now and runs pretty good. I'm sure it will need fine tuning, but bumping up to a 140 main should be a good place to start for most people. It's a joke that lazy retailers sell these as specific kits but with jetting that's not even close to being usable. Hope this helps.
 
#18
Having the same issue. It came with a 95 main jet. Waiting on a 130,135,and 140 jets to try and adjust. This is in a 196 Hisun. While I was waiting ordered a pipe for it. Let’s see.

anyone put a Mikuni on a Coleman ct200u?
 
#19
130-140 will run a lot better on the top end than a 95 main. Keep in mind once you start swapping exhaust and performing other engine mods your jets may need changed again. The Hisun can be made into a heck of a little engine.
 
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