Vitacci pentora 250cc carb issues

[570biker]

Hi maybe someone can help me out. I recently purchased a new vitacci pentora 250cc sport quad. I did the nibbi pe30 carb swap. I cut the manifold adapted a cooper elbow, 48 mm cone filter, NGK plug all the usual upgrades as well as adapted a 788 pro torq CRF 230 exhaust. After chasing a few air leaks I got it all good but I just can't get the jetting right. Right out of the box the nibbi pe30 had a 128 main jet and a 40 pilot jet. It was too rich "black plug". I live in Pennsylvania the elevation here is 460'. I have a jet kit that I purchased from Amazon. I went down to a 32 pilot jet and 115 main jet. Still rich. The 32 pilot jet was the smallest one in the kit. I've been in and out with the air fuel mixture screw and even went all the way down to position one on the needle. Still loading up at idle. I have the same carb on my xpro Templar 250x and that one ran perfectly out of the box with the stock jets and minimal air/fuel screw adjustment . I've been tuning carbs for years and never run into this problem. I'm having problems finding smaller than 32 pilot jets for the nibbi pe30 carb also and I'm not even sure anymore if that's the problem. If anyone has any useful information I would surely appreciate it
Thanks in advance. -Rob

[dirtbkr188]

went all the way down to position one on the needle.

Do you mean you went all the way up to position one on the needle to lean it out?

[570biker]

Yes. I've been from position 3 the middle all the way done to one for lean and still too rich. I emailed jets r Us to see if the have anything smaller than a 32 pilot because Amazon and eBay do not. Even the smaller nibbi pe28 jet kits are the same

[570biker]

I've never had so much trouble with a carb before. I have a xpro Templar x 250 with the same carb right out of the box it worked great. I only had to adjust the air/fuel screw and it was good to go and it's almost the same engine

[dirtbkr188]

When you lower the clip to the bottom slot from the top of the needle, you are richening the mixture by raising the needle up.

[dirtbkr188]

Other than having a "black plug", what does the bike do when you are riding it? Does it blubber like it is getting too much fuel while going through the gears? Is the issue between idle to 1/4-throttle (pilot jet range), 1/4 to 3/4-throttle range (jet needle range), or 3/4-throttle to wide open (main jet range)?

[570biker]

Yes I know it's all the way at the top which means the needle is set now as far as it can be seated in the jet. Making the needle as long as possible. It's as lean as it can go. I've also had the air fuel screw in as far as it will go and then it just stalls out of course. I've done the standard one and a half turns out and have tried adjusting it in or out and it still starts loading up on idle which you can clear out by reving the throttle. Then when it's back at idle it starts loading up until it chokes its self out. It has to be the pilot jet aka slow jet. I just have to find one small enough

[570biker]

It's only idle to 1/4 throttle. Runs pretty good everywhere else. It does give a backfire on deceleration every once in a while with the aftermarket exhaust. It seems like that's due to the build up of unburnt fuel in the exhaust

[570biker]

It's got to be the slow jet but I'm really surprised it's running that rich with a full aftermarket exhaust and a 48mm pod filter. I've been looking on here to see what other people are running for set up and other people are running bigger slow jets and not having any problems

[570biker]

Like I said I've been doing this for years and was a service manager at a bike shop as well as a mechanic for years and I've never chased a problem like this for this long. I had to walk away from it for the day. I hoping that a smaller slow jet will get me close and then I can just tune it

[dirtbkr188]

One last question for you, if you don't mind: Post a few pics of the Nibbi PE30 carb, I'm not 100% familiar with the overall configuration of that particular carb.


Thank you

[570biker]

I'm sorry I'm not near the ATV right now. You can search nibbi pe30 carb on Amazon there are a lot of them for sale and you can also Google nibbi pe30. Thanks

[dirtbkr188]

Will do, thank you

[dirtbkr188]

While browsing around on nibbiracing.com I found their pilot jet kit for the PE carbs, it includes a #30, as seen HERE


It also looks as though the Nibbi pilot jets are a direct copy of the Keihin N424-21 pilot jets, as seen below

[570biker]

Thanks I'll check it out. From what I've seen on threads here some people have used 27.5 pilots also. I'd like to get some a little smaller than just the 30 so I have them here in case the 30 is still too big. I'm waiting to here back from jetsrus.comto see what they have to say