The PZ30B "Pumper" thread.

[Megadan]

Just decided to throw something together for anybody that is considering this carb, but has never dealt with one like it before. If you are considering a Mikuni clone, then I invite you to a great alternative with some performance benefits for any of your throttle twisters out there.

The Carburetor in question is known, as the title suggests, as a PZ30B. Often listed as a PZ30 Accelerator Pump carb on websites like Aliexpress and ebay. In this video I explain the main differences between this carb and the standard one as well as how to do the basic setup on it.




As I mentioned in the video the nozzle for the accelerator pump should be aimed down the middle of the carburetor for proper function. If you test yours and you find that it doesn't, and like mine was spraying the side of the carburetor bore (blue line in pic). You will need to adjust it so that it is similar to the green line.


How you would do that is start by removing the bowl of the carburetor, and then using something soft (a bit of wood or plastic) you will want to pry or tap out the jet. Just be careful not to bend it. Go as gently as you can and apply even pressure. It should eventually pop out.

Once the nozzle is out you will see a notch on one section on the bottom of the jet (yellow arrow). This notch is there to denote what direction the jet is spraying. Simply turn it so that it faces the back of the carb at your desired direction and then press it back in with an appropriate bit of rod or a small roll pin punch. If you want to test the spray pattern before putting the bowl back on, I find that a can of carb cleaner with a straw on it works well by spraying up through the bottom of the nozzle, and its a good way to ensure it is clean.


One other thing you may run into with your pumper carb is that the throttle cam for the accelerator pump has a bit of play in it and may bind up or cause the throttle to get stiff. If yours does this, a thrust washer big enough to sit on all sides of the cam between it and the bracket is a great way to solve the issue for cheap. It will also ensure that the throttle cam returns and hits the stop on the carb body.





The great thing is, with this carburetor you can simply use the same jetting you may be running on the stock style carburetor and transfer it over. It is possible to get two different styles of pilot jets, but the same sizes will translate over between the styles. The difference in how the bike rides/feels is pretty awesome, and hard to describe. Awesome is a good word for it.

[OneLeggedRider]

Very impressive Dan and thorough as always. Would this be a Keihin clone? And can you elaborate on the different pilot jet styles? And would this affect your needle clip setting? And lastly can we know what size jets you're running with your modded head? Enquiring minds want to know lol.

[Megadan]

Originally Posted by OneLeggedRider

Very impressive Dan and thorough as always. Would this be a Keihin clone? And can you elaborate on the different pilot jet styles? And would this affect your needle clip setting? And lastly can we know what size jets you're running with your modded head? Enquiring minds want to know lol.

Yes, this is technically a Keihin clone. There are some goofy exceptions since these are made in China though. Mine is a GREAT example of that. The carb says Mikuni on the body, but uses the Keihin PZ30 bowl. It runs Mikuni main jets, and a Hawk style pilot jet. (Confused yet?)

Most of them tend to run Keihin jets. Like this one: https://www.aliexpress.com/item/KEIH...9-fe9737708a69
Main jet 99101-393
Pilot jet N424-21

While I am normally an advocate for genuine jets, this kit would be a great way to get dialed in if you have one using those jets. https://www.amazon.com/QUIOSS-Carbur...VHS2P6X5MFC282

As far as adjusting the jetting, that depends. As a whole, I would say there is no real changes in jetting needed if you were to go from a stock carb to this one. The one exception to this would be if you are running one or more jet very rich already. In that instance, backing it off a hair and leaning it out would be a good idea to prevent potential bogging.

As far as my jetting. I am running a Mikuni N100.604 125 main jet. Needle in the middle(3rd) notch, and a "45" sized Hawk style pilot jet.

[China Rider 27]

Ah yaa! Sign me up for class! The conversation the past few days about building on the stock carb with the PZ30B got me excited as I realized something sorely needed may start soon to be developed. I have thought the PZ30B the logical carb upgrade since I first started understanding HAWK carburetion some 3 months ago. In fact I sent a PZ30B back yesterday because it had some weird pilot jet I was unable to cross reference on Jets R Us. I ordered another one. The whole lay out from stock carb upgrade to PZ30B progression with parts descriptions and tuning tips is sorely needed. Hats off to Megadan, Hawk guru, for stepping up!

[Megadan]

Originally Posted by China Rider 27

Ah yaa! Sign me up for class! The conversation the past few days about building on the stock carb with the PZ30B got me excited as I realized something sorely needed may start soon to be developed. I have thought the PZ30B the logical carb upgrade since I first started understanding HAWK carburetion some 3 months ago. In fact I sent a PZ30B back yesterday because it had some weird pilot jet I was unable to cross reference on Jets R Us. I ordered another one. The whole lay out from stock carb upgrade to PZ30B progression with parts descriptions and tuning tips is sorely needed. Hats off to Megadan, Hawk guru, for stepping up!

Thank you. We had a thread a while back discussing the pumper carb, but only two or three of us made the leap at that time and it wasn't really discussed further.

In my opinion, short of a PWK/OKO or PE 28 or 30mm smooth bore carb, this is the only real "upgrade" in terms of any performance benefit. The Mikuni is a great upgrade in terms of tuning capability, but otherwise doesn't offer any real performance increase.

The problem you ran into is honestly the one draw back. I ran into the same thing when I ordered mine, but by happy circumstance it used the same pilot jet as the Hawk. The one downside to that is that there are no real options for a new pilot jet - hopefully that will change with NzBrakeLathe's discovery of said jets in different sizes. The one I posted, and a couple others on Aliexpress, come with rebuild kits and a couple of extra jets, which actually lets you see what type of jets they use. The only ones I would buy would be those, just to ensure I am getting something that has jetting options.

The quarter turn throttle is honestly a nice and welcome upgrade to the stock throttle as well, which requires one heck of a range of motion to go from idle to wide open lol.

EDITL I also realized I was missing a picture and updated the first post to include it. Oooops

[OneLeggedRider]

I like seeing the stream of fuel shoot right down the middle of the carb right under the slide as it's going up, that's pretty slick. Puts me in mind of my 800cfm Q-jet. But even if it hit the side of the venturi it would probably net about the same results (I know most of us would be a little wary of tapping that jet out to align it). I'm also interested in the quick twist throttle. Mine seems to have quite a bit of play even after adjusting it.

[Megadan]

Alternative ebay route.

Carb with cable and "rebuild kit" https://www.ebay.com/itm/26342240991...&ul_noapp=true

Throttle assembly. https://www.ebay.com/itm/7-8-22mm-Qu...MAAOSwGtRXxXZ5

Those combined are about 48 bucks.

Fancier all aluminum throttle assembly if you are feeling a bit more spendy. https://www.ebay.com/itm/7-8-22mm-Qu...MAAOSwGtRXxXZ5

The throttles are from US sources with "fast n free" shipping. You can get them from a Chinese source for a few bucks less if you don't mind waiting.

[NzBrakelathes]

I ordered some carbs, jets cables and throttle parts - I will post soon a link etc if that is OK?

[Megadan]

Originally Posted by NzBrakelathes

I ordered some carbs, jets cables and throttle parts - I will post soon a link etc if that is OK?

Yeah, feel free to include a link or two to parts for this carb. It's on topic. I thank you for asking though, very respectful.

[Kivi]

I have a question about the pumper carbs. Does the additional fuel from the pumper circuit lasts only one time or the circuit is active as long as the throttle is twisted?
Does the circuit gives one dose of fuel or maybe vacuum sucks the fuel through pump circuit even after the pump has injected the fuel dose?

[Megadan]

Originally Posted by Kivi

I have a question about the pumper carbs. Does the additional fuel from the pumper circuit lasts only one time or the circuit is active as long as the throttle is twisted?
Does the circuit gives one dose of fuel or maybe vacuum sucks the fuel through pump circuit even after the pump has injected the fuel dose?

That is a great question. Generally speaking an accelerator pump only adds fuel during the initial throttle application, and even then only when the throttle opens at a fast enough rate for the diaphragm to push the fuel out of the nozzle and not just back into the bowl - which is how it is supposed to work.

I guess in technical terms the nozzle could add a teeny weeny level of fuel al the time since it is an open circuit to airflow, but it wouldn't be anywhere near enough to have any appreciable affect. The hole on the end of the nozzle is so small I couldn't really get a good picture of it, if that gives you a good idea. It is literally a pin hole.

[NzBrakelathes]

Originally Posted by Megadan

That is a great question. Generally speaking an accelerator pump only adds fuel during the initial throttle application, and even then only when the throttle opens at a fast enough rate for the diaphragm to push the fuel out of the nozzle and not just back into the bowl - which is how it is supposed to work.

I guess in technical terms the nozzle could add a teeny weeny level of fuel al the time since it is an open circuit to airflow, but it wouldn't be anywhere near enough to have any appreciable affect. The hole on the end of the nozzle is so small I couldn't really get a good picture of it, if that gives you a good idea. It is literally a pin hole.

I took mine apart n it has 2 check valves with a tiny spring and ball - so it loads n unloads each cycle etc

[NzBrakelathes]

As a set a 1 stop place what would you think is the best way to purchase a kit? with what options etc?

PZ30B with fuel line and filter (non cable style)
Dual cable and fast throttle (Not TT250 suitable)
Hand grips
Pilot Jets 42 45 48 50 (I'm assuming after 1st tune kit or should I change that?)
Main jets 103 108 118 (these are in between sizes to 1st tune kit)

Option to buy with the kit a choke cable and bracket for carb

More jets in case folk didn't start with the 1st tune kit?

Also there are possible options to just use stock style quick turn throttle (I'm not sure if Hawk etc stock is what I am use to being stock)

I have a dual cable that MIGHT suit the TT250 so there's a possibility for TT250 owners.

Also quick turn/1/4 turn throttle has the ability to be used on stock PZ30 carb (cable and throttle part) Could even add a choke cable to this set up.

So many options!

[Wild Dog]

Well i was able to get a rebuild kit for the P30B. At first i was afraid of the price, because the last kit i bougth was for an original VM26ss, the float alone cost me 30 usd for that thing, because it was not common...

But lucky me, the whole kit for a P30B, was just 2 USD so i got one for the CG200.



It came with everything to refurbish it.



I was a bit afraid to remove the top part of the main jet, but with a plastic punch i was able to take it off with ease.




The new part was a bit longer, but it did fit right.




Refurbished

[NzBrakelathes]

Originally Posted by Kivi

I have a question about the pumper carbs. Does the additional fuel from the pumper circuit lasts only one time or the circuit is active as long as the throttle is twisted?
Does the circuit gives one dose of fuel or maybe vacuum sucks the fuel through pump circuit even after the pump has injected the fuel dose?

Remember old school Holley carbs? With accelerator pumps? It just “spits in” a shot of extra fuel on hard acceleration