Carb tune and jet sizes
 

I know this is discussed to death so i just wana ask when yall are talking about jet sizes what brand jet sizing is everyone as the standard when talking jet sizes here? I have a pz30 that came with what im assumig is a keihin jet kit. I found ths awesome conversion chart here
https://www.jetsrus.com/FAQs/FAQ_mik...ihin_sizes.htm

So i think i can figure it out but now i see dyno jet has its own sizing as well. Are there any other to know about? Is there a way to tell a difference between types of jets by looks? i dont remember seeing labels except size #
Thanks for any time time and help

I think PZ30 and the pumper PZ30B run a 38 and 115 from memory which is a ballpark base line. Some of the clones carbs though do not use standard keihin jets...so you really need to inspect the carb jets to confirm a parts match...


But to answer the question a keihin M5 jet kit should work on the PZ30 and Nibbi PE28

I believe you will find with the PZ30 that the pilot jet cannot be replaced. The Chinese made it proprietary and it can not be found. You are stuck with the 40 they put in it. Then, the needle cannot be adjusted down, only up and only with spacers. Finally, the airscrew is on the bottom of the bowl and almost impossible to get to for adjustments while the engine is running. But hey, you can change out that main jet all day long!

I say take that PZ30 and throw it in the trash. Get a Nibbi carburetor, then you will be able to make all those adjustments properly.

While I still think the PZ30 is crap, apparently you can swap in a needle that is able to be adjusted. I bought this needle/jet kit:

https://www.amazon.com/dp/B0CHM8J55P...roduct_details

Since I have not thrown it in the trash YET, I decided to just eyeball and see if the needles are swappable, and they appear to be. In fact, the position of the clip is exactly at position 2, or second from the top. So there's that.

The PZ30 does the thing, but just not very well. I couldn't believe how well the Nibbi did on a cold start. Then just looking at the internals...quality polished metal as opposed to rough casting with inferior metal.

Actually, you CAN find the pilot jets.

These are two piece jets, and all you have to replace is the jet port side. It is explained here:
https://www.chinariders.net/showthre...ighlight=storm

That thread and the links noted in that thread show these jets:

Attachment 30460

The pilot jet leaves behind the second piece in the port when you change them:

Attachment 30461

I found these pilot jets on AliExpress and ordered them. If you Google this description, the AliExpress listing for them will show up in the results "(12pcs pilot jet / pack)Motorcycles modified with a cold start short carburetor pilot jet nozzle vice injectors Nozzle"


Attachment 30462

You can always buy a new carb and start all over again jetting! But the original carbs work fine once jetted and adjusted, and you already know how it is running (probably a bit lean!). All you need to do is shim the needle, bump the jets sizes by one step, and then adjust the airmix screw after some testing. Chances are you will be jet OK then. Needle shimming is described on the Templar 250 resource thread (sticky at the top of this section). My Storm runs great with the original PZ30. Nice Carb. My Temp X also has the original Youall smoothbore carb. It is excellent!

Thanks for the info guys but thats not what i was asking, maybe i worded wrong i have a brain injury plz forgive Like i said all this has already been talked to death. I do have a genuine pz30 keihin, which came with a jet kit that i have already worked on. Its been sitting for a year and needs a cleaning and i might play with the jetting

AND I WAS JUST WONDERING WHEN EVERYONE TALKS JET SIZES which jet sizing are they using as a standard becuz thy hardly ever say? Seeing how just from that one conversion chart there are 3, mikuni keihin, and dynojet and thy are all different..... when someone says 115 main 45 pilot is that mikuni, dynojet, keihin, or maybe even some other metric? not here for the d**ck measuring contest just wondering haha. Thanks.

Sorry. You mentioned the original PZ30 that came with the bike in your first post. I assumed that was what you wanted advice about. As I mentioned, bump the pilot and main jet one size, shim the needle ~1mm, and then work on airscrew adjustment if you want to go with that carb. That's my answer. Just trying to help.

I am pretty sure that the 115/45 numbers are keihin metric. This is the same scale used on the replacements I get for the PZ carb.

I have found that the numbers on various Chinese clone jets do not match the same bore hole sizes for the "same" number from the genuine Keihin or Mikuni jets they're copying. I have not found any rhyme nor reason to it and I've subsequently given up.


My strategy is this: The genuine jet size charts include the actual size of the hole in them. You can use one of those master drill bit sets (I have the 115 piece one from Harbor Freight which works fine) and you can use the shanks of the tiny bits provided to probe and ascertain what the bore hole size is in actual decimals of an inch -- never mind the number stamped on the jet -- and use that to determine what size you actually have. You can test your replacement eBay/Aliexpress/Amazon clone jets the same way to determine which ones are larger or smaller.


If you're brave you can also re-drill the jets to your chosen size, but I'm too lazy for that when a kit of 12 is just $10, or whatever.

Thanks thumper! I was just wondering. Ive already gotten into this with ppl on here with the whole keihin doesnt make an aftermarket original pz30 , that its a clone. Well i have a pz30 woth keihen stamped into it and it is a bit different from the stock. The needles different actually has different noches no need for shiming...and some other slight differences. After doing some research everyone was half right. It is a keihin but made by a subcontracted company, which is a common business practice the subcompany is supposed to still meet keihins standarrds...So ya lol and i do have an awesome jet kit that came with it, with the different metrics and carbs being so sensitive i figured there would be a standard metric everyone is using.. i guess i should assume mikuni has mikuni jets and pz uses keihin?

Cool. I'm still way happier with the Nibbi. As stated, the PZ30 does the thing, just not very well. Inefficiency in build quality translates to inefficiency in operation, no matter what the product.



Wait. What the hell was your question again?



So, you received a jet kit with the carb and you're wondering about jet kit manufacturers. Why? Were you TRYING to start a d*** measuring contest?

Very interesting ya i have considered drilling thm out but with amazon prime why not just buy the kit with the aftermarket carb lol but thats really good to know the clone jets dont even match up might just drill em out now. Got plenty of spare jets and the stock carb so why not. I wonder how precise matching a drill bit to a hole size is tho if that is how you are measuring if im understanding correctly. Good things to think about tho thankyou

I have heard about variability in the ports of these cheap jets. So far, I have gotten consistent jet bores on all of the cheap jets I have gotten. And, I paid under $30 for all of them for two motorcycles with many spares up and down the scale!

I do compare the bore when I remove the one I am replacing, comparing it to the one I am putting in. And I have a full range so I can look at them in series. I hold them side by side looking through them to a light source. You can see the differences. Pilot jet has an airscrew fine tuning option, so it may be a little more forgiving and flexible.

Stock carb here,just needed a little love.