Question about predator 212 @ higher rpm’s

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devlinrules12

New Member
#1
#1
Hey so I have a modified predator 212 non hemi with the current mods

Billet rod
Billet flywheel
Gov delete
22mm nibbi carb(jets are 35pilot 140main)
18# valve springs

Now previously I had a 22mm knock off Mikuni carb but I swapped to the nibbi because I could not find the correct pilot jets for it . When I was running the knock off carb though I was able to run WOT @7,000rpm’s around 50mph .
However since switching to the nibbi when I’m at WOT I get to about 5,500 - 6,000rpm and it feels like the bike is cutting out and doesn’t want to climb anymore . I’ve switched main jets from 120 all the way to 140 with same results. Do you guys think I’m running too rich or lean? Plug looks pretty tan . I’m also running clear fuel lines and can see the gas so I don’t think I’m running out of fuel .
 
Minimichael

Minimichael

Well-Known Member
#4
#4
What's your needle position? You might wanna try dropping the clip all the way down and get that stock, too-long needle up outta the hole. Raising the needle should let more fuel in. Just guessing here. But if you can't feel the difference between a 120 and 140 main, it could be the needle isn't getting out of the way.
 
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devlinrules12

New Member
#5
#5
Minimichael said:
What's your needle position? You might wanna try dropping the clip all the way down and get that stock, too-long needle up outta the hole. Raising the needle should let more fuel in. Just guessing here. But if you can't feel the difference between a 120 and 140 main, it could be the needle isn't getting out of the way.
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Right now I’m in the middle I’ll try lowering it and see what Happens. But correct me if I’m wrong here I always thought the needle only affected 1/2 to 3/4 throttle while the main jet affects full throttle ?
 
Minimichael

Minimichael

Well-Known Member
#6
#6
What if, at your point of widest and openest, the needle's still too far down inside the jet hole thing? Maybe that nice tapered end of your needle isn't even in play yet? This would mean your main jet isn't allowed to reach it's full potential. This would be similar to my own Nibbi experience, anyway. I found keihin 26 needles (about 1mm shorter) performed better than the one stock needle that Nibbi makes and sells. The nibbi's throttle body is wider and allows more flow than most, but I also think that wide short slide area leaves the venturi effect a little harder to tune for and capture, especially near the top. I mean, we already know your engine can spin more air. What seems to be missing is the motivation. My guess is the ideal taper position of your needle, when you're pulling at WOT, is still buried inside the jet hole a bit. Bringing it up and out more might give you a healthier fuel mist. And more bang.
 
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devlinrules12

New Member
#7
#7
Minimichael said:
What if, at your point of widest and openest, the needle's still too far down inside the jet hole thing? Maybe that nice tapered end of your needle isn't even in play yet? This would mean your main jet isn't allowed to reach it's full potential. This would be similar to my own Nibbi experience, anyway. I found keihin 26 needles (about 1mm shorter) performed better than the one stock needle that Nibbi makes and sells. The nibbi's throttle body is wider and allows more flow than most, but I also think that wide short slide area leaves the venturi effect a little harder to tune for and capture, especially near the top. I mean, we already know your engine can spin more air. What seems to be missing is the motivation. My guess is the ideal taper position of your needle, when you're pulling at WOT, is still buried inside the jet hole a bit. Bringing it up and out more might give you a healthier fuel mist. And more bang.
Click to expand...
I will try this out and see how it goes thank you
 
D

devlinrules12

New Member
#8
#8
Minimichael said:
What if, at your point of widest and openest, the needle's still too far down inside the jet hole thing? Maybe that nice tapered end of your needle isn't even in play yet? This would mean your main jet isn't allowed to reach it's full potential. This would be similar to my own Nibbi experience, anyway. I found keihin 26 needles (about 1mm shorter) performed better than the one stock needle that Nibbi makes and sells. The nibbi's throttle body is wider and allows more flow than most, but I also think that wide short slide area leaves the venturi effect a little harder to tune for and capture, especially near the top. I mean, we already know your engine can spin more air. What seems to be missing is the motivation. My guess is the ideal taper position of your needle, when you're pulling at WOT, is still buried inside the jet hole a bit. Bringing it up and out more might give you a healthier fuel mist. And more bang.
Click to expand...
Ok so I moved the needle setting down with no luck .

After this I decided to get a couple new spark plugs and try rejetting again . I went all the way down to a 115 this time and put the bike up in the air and what do you know it revved past 7,000 rpm’s but the new plug was super white . I then swapped in a 120 and the bike is back to only revving around 6,000 rpm’s and the plug looks a little better . Not sure why this is happening
 
ole4

ole4

#10
#10
so you are holding the wheel up in the air and revving it to 7000 RPM? I thought you were riding it at 7000 RPM and doing 50 MPH. What was the installed height of the 18lb springs? I would think you would float the valves at 7000 rpm.
 
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devlinrules12

New Member
#11
#11
ole4 said:
so you are holding the wheel up in the air and revving it to 7000 RPM? I thought you were riding it at 7000 RPM and doing 50 MPH. What was the installed height of the 18lb springs? I would think you would float the valves at 7000 rpm.
Click to expand...
No when I had the knock off mikuni installed I was riding going 7,000 rpm @50mph and would run WOT fine. I just could not find the correct pilot jets for that carb. So I switched over to the nibbi carb where I’m having the issue riding or holding the wheel up . And I did not check install height…
 
Minimichael

Minimichael

Well-Known Member
#15
#15
Maybe the 120 jet is getting too big for this-sized Nibbi? You might as well try dropping the needle a notch or two, with the 120 still in and see if that changes anything.
 
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brookbank85

New Member
#16
#16
devlinrules12 said:
Hey so I have a modified predator 212 non hemi with the current mods

Billet rod
Billet flywheel
Gov delete
22mm nibbi carb(jets are 35pilot 140main)
18# valve springs

Now previously I had a 22mm knock off Mikuni carb but I swapped to the nibbi because I could not find the correct pilot jets for it . When I was running the knock off carb though I was able to run WOT @7,000rpm’s around 50mph .
However since switching to the nibbi when I’m at WOT I get to about 5,500 - 6,000rpm and it feels like the bike is cutting out and doesn’t want to climb anymore . I’ve switched main jets from 120 all the way to 140 with same results. Do you guys think I’m running too rich or lean? Plug looks pretty tan . I’m also running clear fuel lines and can see the gas so I don’t think I’m running out of fuel .
Click to expand...

so did you figure out anything with your jetting. I am running a Nibbi PE24 and it runs great on any main or pilot. I'm at 950ft and currently running 130 main and 38 pilot. I think tomorrow I am going to step up to a 42 pilot until i go rich, Right now I can't get a plug to change colors. Just stays pretty much brand new looklng after 10 hours of riding and idling. RPM when WOT stop at 3800 rpm
 
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hermans13

Active Member
#17
#17
If the plug stays like brand new after 10 hours, you are running lean. It should be looking toward the tan side. Your plan on going up in pilot size is a good one. Please keep us advised.
 
sparkwizard

sparkwizard

#18
#18
Go up on MAIN jet size if you run wide open, plug looks new and you only get 3800 RPM.

Right?

Does it pop, spit and backfire at WOT?
 
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brookbank85

New Member
#19
#19
It doesn't pop, spit or backfire at all. Runs clean at all times just the limit of 3800 rpm. Seeing i have the 130 main already in it thats why i want to step up the pilot to see if it will balance out
 
sparkwizard

sparkwizard

#20
#20
Your altitude will cause it to run lean. My uneducated guess would be to fatten up the mixture at all throttle positions.
That means bigger main and pilot. Maybe try a restrictive air filter to see what happens.
Tuning a carb is the process of making it work with your combination of engine parts, riding style and your ENVIRONMENT.
Most of the basic recommendations are coming from people closer to sea level. At 1000 feet above sea level, you will run lean if you follow those suggestions. Go big.
 
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