Idle to WOT bog

[aaw611]

I'm sure this has been beat to death here but I couldn't find anything specific on it. I've got my carb tuned up pretty much exactly where I want it but I'm having one issue that is still nagging. I'm running a foam air filter, a PZ30 clone (not the stock carb), a 35 pilot, a 115 main, needle in the lowest (richest) notch, and mixture screw about two turns out. It uses this style of jets:


https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1



The issue I'm having is a bog when I go from idle to full throttle. It revs up perfect if I give it a little more time to go WOT but if I go to WOT quickly it will bog and sometimes even stall. It almost got me in trouble in a parking lot once when I needed to avoid an idiot. I have +5 and -5 on the main, up and down on the pilot, and tried just about every 1/4 turn increment on the mixture screw. Tonight I moved the needle into the lowest setting, it was on the second richest before. I took it around the block and it seemed to pull harder, which I'm excited about, but the bog issue is still there. Its only there from idle. It doesn't happen on a WOT pull from 1/4 throttle.


Is this just a shortcoming of a non-pumper carb? Perhaps its sucking too much air with the foam filter? What do you guys think?

[aaw611]

BTW, I'm watching Megadan's pumper carb video right now!

[China Rider 27]

You do not say on what engine you have this carburetor but I assume a 229cc CG type and that it is stock other than the POD filter. The standard tune as you can determine from the forum in a PZ30 stock carb is 40 pilot and 110 to 115 main.

You do not say exactly where the bog is but I bet just off idle. This is the area where the transition from pilot jet to needle jet happens and where I have had some issues. I have a carb on bike starts beautifully, idles as good as any carb I have used but when cold just coughs and sputters with throttle application until it warms up and then it will run like a bat outa hell but has also backfired twice at speed with a close of the throttle. It has kept the same tune across a 47 degree temperature swing from 50 degrees to 97 and run passably spring to summer. Go figure.

Something about the air flow across the jets or the shape of slide or internal machining affecting metering.

The thing to remember is these are cheap Chinese clones (CCC) carburetors. I figured up the other day I have a 66% success rate which means 33 out of hundred are machined paperweights.

What I do is try all the adjustments then move on to better utilize my time but there is a case to make here for putting more money into a better carburetor which in the long run might save money but then, that will not make you a better carburetor tuner.

[aaw611]

Yep, it's a CG on a Hawk. The bog is off idle when full throttle is applied. Its like it's getting drowned with a blast of fuel from the main (doubtful) or sucking a massive breath when the slide opens with not enough fuel to compensate. I have tried larger pilots, like a 40, and the bike spits raw fuel out the pipe. These are Amazon fake Kehein jets though, so no idea how true to size they are. I may just end up calling it a quirk of the bike and learning to deal with it!

[TheChairman]

I'd try dropping the needle a notch or two first. It could be overfueling at that transition point.

If that doesn't work, you can start questioning the carburetor or the jets themselves. As is stated above, the Chinese clone carburetors are notorious for being junk. They work, but they don't compare to a real Japanese made unit or even a good Chinese unit like the Keima's that CSC uses or a Nibbi.

[gwowzer]

My Nibbi bogs from idle when given just a slight amount of throttle when the bike is hot. If the bike is not all that hot it runs great. I'm thinking that I have it as tunes as it's going to get and there are always just little things that are going to happen with a carved bike. I have switched and swapped and adjusted so much without it being oerfect... just so much you can do lol

[China Rider 27]

Originally Posted by aaw611

I may just end up calling it a quirk of the bike and learning to deal with it!

The good thing about a (CCC) is they are inexpensive. A PZ30 $20 bucks or so. You have the jets. The odds may turn in your favor. The worst it can be is another carburetor tuning lesson for $20. Live with it! Nah!

[aaw611]

So, you're thinking it's worth trying another PZ30 or similar because there is a chance that the airflow or transition between jets may be smoother and eliminate the rough spot?

[Digger]

Out of curiosity. Has anyone checked if the slide cutaway is the same from the stock carb and the Mikuni
clone?

[China Rider 27]

Originally Posted by aaw611

So, you're thinking it's worth trying another PZ30 or similar because there is a chance that the airflow or transition between jets may be smoother and eliminate the rough spot?

Yes I would not accept a carburetor that did not function well across the board from idle to WOT and a PZ30 can work as it is the stock carburetor for the HAWK and I know they can run well, I have one runs great. Many have had trouble with them, but you can have trouble with ANY of these inexpensive carburetors. I saw a PZ30 on Amazon for $16.00, if it works that would be a steal. A lot of these carbs are getting good reviews and appear to working for somebody?