PZ27 vs PZ30 Carb Upgrade

[kevshek]

My bike is a 2009 Shineray XY200GY-4, 200cc 4 stroke engine. I dont know which bikes they are the same as but im sure lots of people on here will know.

The original carb fitted to the bike is a SHENG WEY PZ27. While searching around for Shineray parts on ebay, i came across a Mikuni PZ30 carb, which was comfirmed to me, was fitted to 150 to 250cc bikes/quads. So i thought id take the plung and try one out.

First off, heres some pics of the 2 carbs.
PZ27 to the Left, PZ30 to the Right.
http://i71.photobucket.com/albums/i132/kevshek/bike/DSC_0187.jpg
http://i71.photobucket.com/albums/i132/kevshek/bike/DSC_0188.jpg
http://i71.photobucket.com/albums/i132/kevshek/bike/DSC_0189.jpg
http://i71.photobucket.com/albums/i132/kevshek/bike/DSC_0190.jpg

PZ27 uses these types of jets, size 40 Slow jet, 86 Main.
http://i71.photobucket.com/albums/i132/kevshek/bike/DSC_0191.jpg

PZ30 uses 20 Slow jet, 100 main (standard)
http://i71.photobucket.com/albums/i132/kevshek/bike/DSC_0193.jpg

The first noticable difference is that the carb is bigger obviously, which made it a bit harder to fit. The choke levers (not all pictured) were different aswell as mine is cable operated, but the mounting points are same so it was a simple swap over.

Fitting wise, now that ive done it numerous times, this is the easiest way to get it in between the frame. Its best to leave off all the choke stuff to reduce its overall size, or you wont get it in. You can refit it once the carb is seated inside the frame.

Place it into the frame at this angle
http://i71.photobucket.com/albums/i132/kevshek/bike/DSC_0175.jpg

Make sure the protruding parts on the right side are under the bracket.
http://i71.photobucket.com/albums/i132/kevshek/bike/DSC_0176.jpg

Then you can ease the left side into the corner and past the frame.
http://i71.photobucket.com/albums/i132/kevshek/bike/DSC_0177.jpg

Finally, its a simple case of spinning it into position. The best way to do this is to push the carb inlet into the rubber airbox tube, as this is flexable, then line up the outlet flange onto the intake manifold**.
http://i71.photobucket.com/albums/i132/kevshek/bike/DSC_0194.jpg

**I have replaced the manifold studs for bolts which are easier to fit in that restricted space. I also cut a slot in the bolt head, this way i could screw them in most of the way with a long flat screwdriver, and tighten with a wrench.
http://i71.photobucket.com/albums/i132/kevshek/bike/DSC_0174.jpg

Tuning notes to follow....

[kevshek]

Onto tuning. In standard form, the PZ30 came with a 20 Slow jet and 100 Main jets, but after first install and running, i could tell there was a fueling issue straight away. The bike started and idled no problem, and revved in neutral no problem, but when riding, there was low torque and low top speed.

After a quick search on the net, i found a generic carb tuning guide and set about applying its advice. This is what i understand, but please correct me if im wrong.

Top End Tuning
Basically, low top end speed at full throttle meant that my main jet was too small, and the bike was lean. So i decided to order a range of jets from 110 to 130 in steps of 5. As i had also installed a bigger rear can on the bike around this time, i decided to jump straight in and fit a 120 jet. This was a much better improvement. The bike felt stronger and pulled slightly harder then usual. Top speed is a fraction higher, but higher speed easier to get to and maintain.

Mid Range Tuning
This is done by the needle inside the slide. When revving up through the rev range, if the bike feels like its holding back, then the needle needed to be raised. In standard form, it was bang on in the centre, which was fine by all accounts, but i decided to raise it up 1 slot, so it was in slot 2 of 5, counting from the bottom up. This means when you turn the throttle and open the slide, the needle will unseat allowing more fuel, sooner.

Low Speed Tuning
This is the tricky one, and the one im still working on. This is done by the Slow jet and controls the idle and low speed mixture upto 1/4 throttle, from what i believe. Idling isnt the issue here, its part throttle and backing off the throttle. Im finding part throttle unstable and the bike stumbles a bit. There is an adjustment screw on the engine side of the carb which is supposed to adjust this, but i could have the wrong size slow jet all together. The arrox#w in the picture below points to this screw.

http://i71.photobucket.com/albums/i132/kevshek/bike/DSC_0193.jpg

I started off by having this fully in and gradually backing it off 1/4 turn at a time in between rides. So far, im about 2 turns out and still working on the lumpy part throttle issue. To be honest i dont fully understand how this screw effect the engine so if any could explain it, that would be great.

I do know however, slow jets for mikuni carbs are hard to come by in the UK so until i can get some proper advice, i wont be buying any, anytime soon.

[Weldangrind]

I have some experience with that engine, in both the original Honda XR200R and the current China clones. It's MHO that the 20 slow jet is too small. I'm unable to properly tune a 200cc clone or Honda with less than a 25 slow jet. Until you change it, you're not likely to see an improvement.

The key (that I learned from Waynev on this forum) is the amount that the pilot screw is backed out. If you need to back the screw out more than two turns, the slow jet is definitely too small. I installed a slow jet on a buddy's scooter that was on the large side, and I hardly backed out the pilot screw at all.

The pilot screw essentially adds fuel to the stream during the transition from the idle circuit to the main circuit.

[kevshek]

thats what i needed to hear, thanks, again!
ive backed it out 2 turns and more, and there hasnt been any difference. So on the hondas, what size jet were they running? This way i can buy a couple of size from that point on.

[Weldangrind]

I don't know that specifically, because the old Hondas used Keihin carbs with a slightly different numbering system. What I mean to say is that I've used Mikunis on old Hondas as well as new clones.

Several of us on this forum have 200cc Honda clone ATV engines that aren't happy until they're fed with a 110 main and 25 slow. That seems to be the best combo with a free-flowing air filter and muffler.

I prefer the 30mm Mikuni clone to the 30mm Keihin clone. The Mikuni has a better casting, and jets are much easier to find. Will www.jetsrus.com not ship to you?

[kevshek]

Hmmm, seems a bit of a hassle, no direct shipping (see below), but im sure i can find some on ebay, i just need to identify the correct fitment. Ill get a 25 and 30 to be safe.

"To protect your low prices the following method is used for international orders. We apologize in advance to our many honest customers for this inconvenience:

1) Best method - have the item purchased by us credit card holder and mailed to someone in the USA.

2) We accept Money Orders and Certified Checks (funds must be in US dollars). We DO NOT accept personal checks.

3) We accept USA Dollars, however realize that there is a risk sending cash and we are not responsible if the cash is lost or stolen in the mail. If the decision is made to ship the cash it would be advisable for the sender to insure the package for the amount of cash in it."

[kevshek]

found this
http://www.pjmotorsports.com/index.html
Mikuni VM28/486 Pilot Jet
28.1mm in length with a 5mm Head
Believe this is the one i need.

[kevshek]

Just ordered some from http://www.allensperformance.co.uk/
here in the UK, should be with me on monday, i ordered 3 jets, totaling £13 inc postage, not bad.

[Weldangrind]

That's less than a three hour ride. Get on your bike! :lol:

Glad to hear you've found jets locally. I bet that the 25 will be the ticket, unless the weather becomes very cold.

[kevshek]

yeah I think you're right, I've bought 25, 27.5 & 30 just incase.

I can sense your itching to tell and wanting me to ask, so I will, lol
Are you an ex-pat? Cos you know the UK.

I do have another bike, a ER6f which was put away for the winter, but due to the shineray being out of action, I'm using it. Plus the weather is dry, cold but not freezing, so it could have been a possibility. However I am the bike how tomorrow, well traveling down there tomorrow for Saturday.

[Weldangrind]

Nope, I'm a Canadian, but I have roots in the UK. I've been to Gloucester and London, but the rest is just general awareness, particularly about Newcastle Brown. :D I'd love to visit again.

I was kidding about the three hour ride; one thing I observed while in the UK was that people rarely strayed that far from home. It's a notable cultural difference, since we drive 12 hours to visit my parents. :lol:

For the price, I think it's a good idea to have the three slow jets you selected. You'll likely need a jet on the fatter side if the weather is cold.

[kevshek]

Found the thread!
So this PZ30 i have is a copy? even though it has the Mikuni name and uses their just?

Ive tried the 25 pilot jet, then onto the 27.5 and now im on the 30 jet trying to get rid of the lumpy part throttle when cruising. Surely it cant need a bigger jet again can it?

[Weldangrind]

I'm glad you found this thread; the pics provide some clarification. I wouldn't refer to your new carb as a PZ30, but rather a 30mm Mikuni. That's where I became confused.

Your carb is definitely a Mikuni (vs a Keihin), and you can tell that by three bowl screws instead of four.

[Weldangrind]

I can't imagine that you need anything bigger than a 30 slow jet. In fact, I'm surprised that it will run with a 30; I presume that a 25 would be better for a 200cc. I'm going to read your other thread and review the symptoms.

[kevshek]

thanks for the efforts, i await your advice.

[Weldangrind]

This is a quote from your other thread:

Okay, so over the past couple of weeks, ive had to resort in trying the bigger slow jets i ordered, as the 25 still had bad low throttle responce.

The needle jet is fully up so thats not the issue i believe. First i change the slow to the 27.5, which id make it better, but even after tweeking the air screw, it was still hesitant/rough on part throttle where you just need to run at a steady 30 mph (for example)

This week i finally decided to go for the 30 slow jet, again a minor improvement, but still a bit rough on part idle.

Ive only now notice that the bike runs worse the more you open the air jet, so ive ltteraally got it about 1/8 turn from closed. But the more you close it, the worse it idles. Can you actually run the bike with the air screw fully closed? Is that recommended? And what it the best way to be adjusting it. I know that 2 turns out means a bigger jet, but i dont actually know how to adjust it as such.

I'll ask a few questions for clarification. For starters, when you say the needle jet is fully up, do you mean that the clip in the jet needle is in the bottom position? If so, that's likely too rich. Try moving the clip up one notch and tell us if there is any improvement.

You're trying to establish a smooth transition from the idle circuit to the main circuit, so each step requires a proper A/F ratio. My guess is also that the slow jet is too big, but I recommend that you make one change at a time.

[kevshek]

yes, i have the clip at the very bottom motch, meaning the needle is in the highest position. I will try raissing the clip up one to bring it down slightly, but you are right, its the transition between the slow and main ciruit.

Can you explain how the air screw works? Ive noticed if the screw is fully closed, the bike begins to stall. ive so far got it about 1/4 turn open, anything more than that doesnt seem to make any difference, and never has done with any of the other sizes i tried.

[Weldangrind]

In your application, it's a fuel screw, not an air screw. It provides the transition from idle to main, and it is directly related to the slow jet size. IOW, if your slow jet is too small, you'll need to open the fuel screw (AKA pilot jet) more than two turns. If you hardly need to open the screw at all, the slow jet is on the large side.

Looking forward to hearing what a clip adjustment does.

[kevshek]

Mate, you've only gone and done it again! I've adjusted the clip this afternoon and my ride into work tonight was silky smooth! There is no hesitation at part throttle, the transition to the main circuit is seemless, even backing off the throttle and reapplying it during higher revs, the engine doesn't jerk about.

Can't thank you enough!

With the addition of tightening up the engine mount bolts, and replacing the one that was missing which gave the bike a horrible vibration, the bike feels great and should now be ready for winter, which is just Sewell cos today we've had the first snowfall albeit very light.

[FastDoc]

Weld knows things.

Snow is evil.

[SpudRider]

Weld knows things.

Snow is evil.
X2 on both points, oh wise physician. ;)

Spud :)

[Weldangrind]

:D

Glad to hear it, kevshek! In the words of Doc, I'm happy to serve.

[Frog]

Hi Kevshek,

did your new carb improve performance at all?

Cheers

Frog

[akvilonBrown]

Hi everybody!
I'm glad to have found this topic.
My carburateur is PZ30.
I can't get him to warm up the engine properly because it doesn't react to choke lever.
It only stops when choke is 100% closed. Other positions nearly don't affect the engine run.
I have to partially open the main throttle in order to keep warming up.
By the way when throttle is slightly open this way, there is difference between positions of the choke.
Something wrong with idle circuit.
Engine doesn't response to pilot screw much - now it turned out on 2.5 turns.
It has however good response on idle (horizontal) screw.
In other ways it works perfectly, espesially when fully warm.
Need some advice with that dead choke how to force it work.

[Weldangrind]

Welcome akvilonBrown!

Please feel free to start a new post, so that more people will be able to read it and try to help.

My feeling is that the slow jet is either partially clogged, or it's too small. If you remove the pilot jet and tell us what size it is, we can guide you from there.

[akvilonBrown]

Welcome akvilonBrown!

Please feel free to start a new post, so that more people will be able to read it and try to help.

My feeling is that the slow jet is either partially clogged, or it's too small. If you remove the pilot jet and tell us what size it is, we can guide you from there.

Thank you Weldangrind, for your welcome and reply.
Maybe to early for separate post, it's just small reconnaissance. Kind a small step cause it's still warm weather and I don't have so much trouble with warming up. But afraid of the fall coming.
To be honest I'm complete newbee and require some crash course.
Can I remove the pilot jet without dismantling the carb? Is it about unscrewing the pilot screw or it wants dissasembling the carb body?

[FastDoc]

Turn off the fuel. Remove the bowl screws, 3 or 4 I forget on your carb. You may have to remove or loosen the carb body to get to the screws. Carefully slide out the pivot pin for the float and the jets will be visible to unscrew with a good fitting flat blade screwdriver. Do not lose the float needle valve.

I encourage you to look at www.dansmc.com for his on line course for more detail. :D

[akvilonBrown]

Turn off the fuel. Remove the bowl screws, 3 or 4 I forget on your carb. You may have to remove or loosen the carb body to get to the screws. Carefully slide out the pivot pin for the float and the jets will be visible to unscrew with a good fitting flat blade screwdriver. Do not lose the float needle valve.


That was simple!. I haven't even lost anything. :D
So how could I measure those jets?
I can tell only marks on them.
Main jet: 145KB
Slow Jet: K40A

Does it make sense?


I encourage you to look at www.dansmc.com for his on line course for more detail. :D
Great stuff! Your FAQ no worse too.

[FastDoc]

Those marks are the sizes I think. Weld will tell you the specifics. Dan has a good site. I've been wrenching for 35 years and I still refer there sometimes.

[Weldangrind]

I can't tell you the specifics about the Keihin (and clones), but I can guess. The slow jet number is likely to be #40, but I'm not sure how to interpret the main jet. Main jets are usually in the neighbourhood of #100.

The 30mm Mikuni is much easier to work with, because jets are easily found. Depending on the Keihin clone you have, it might be very difficult to source replacements; that's why I switched to Mikuni.

With a stock muffler and airbox, I'd likely use a #110 main and a #25 slow jet in a Mikuni.

[akvilonBrown]

Well, maybe I'll consider replacing too if the things get worse in cold weather.
Is there anything I should take into account additionally?
Like measuring air intake sizes or parameters (by the way, is it worth to install free-flow filter with new carb?)?
Or is it enough to pick up the exact replica from Mikuni, meaning same parameters, for 200 cm engine with 2,6-3 liters per 100 km?

UPD: Loking for the Mikuni PZ30 and on the pictures on the first page of this topic I couldn't spot the 'boosting pump' (correct me if I wrong). You can see it on the right side of my carb with a throttle cord splitting to that pump as well. It adds up fuel during quick pulling the throttle cord. Does Mikuni PZ features the same thing? I'm happy how my carb works on warm state and how it accelerates, I'd like to retain these conditions.

http://img14.picoodle.com/i55d/akvilonbrown/kfua_959_u91kt.jpg

[Weldangrind]

The 30mm Mikuni carbs I've installed do not have an accelerator pump.

[akvilonBrown]

There is no need to replace my carb, I conclude. I just have to adjust idling and/or pick up the right pilot. But I have to know how the stuff works. I went across dozen of sites with carb basics, but I need to clear up. And I found some posibility to pick jets for Kehlin based on their measurements.
We have here: throttle stop screw and pilot screw.
Throttle stop screw - it controls how wide throttle is open in resting position, right? And when I turn in, RPM goes higher. I presume, it shouldn't be open wide.
Pilot screw. Isn't is the same as air screw? What does it do? According to theory, when the threw is on the back (close to air intake?) it regulates the amount of air flowing through the idle circuit. If it is in front, it regulates the fuel. Well, that must be my case.
So, when I turn out pilot screw from the gentle seat position engine doesn't react. Only after 2,5 turns the engine begins to slow down and stops.
I need to understand the behavior: turning out = richer mixture? or vice versa. What pilot jet should I install - bigger or smaller?
That choke behavior - may it be something wrong with air passage on idle? Maybe bigger air jet?...

[Weldangrind]

I'm not as familiar with your carb and the enricher circuit (or pumper), but I get the basics.

You've got it figured out. If the pilot screw is on the engine side of the carb, it's a fuel screw, and backing it out increases fuel flow. The slow jet (or idle jet) within the bowl is responsible for idle, and you have a good grasp of how the idle screw works; it's just a screw contacting a ramp on the slider. Once you open the throttle, the pilot mixture screw creates the transition from slow jet to the main jet. The needle that seats in the main jet is directly connected to the throttle cable, and the the needle is tapered. As the throttle is opened, the taper is raised and more of the main jet is uncovered. The venturi action of air passing through the carb draws fuel up through either the slow jet or the main jet, depending upon whether the throttle is open or closed.

If you need to back out the pilot mixture screw more than two turns, your slow jet is likely too small. An increase of two sizes will likely be helpful.

Make sense?

[akvilonBrown]

Enricher pump - don't mind it, it doesn't tamper with other circuits, it is standalone unit. The rest is classic PZ30 carb.

You wrote:

If you need to back out the pilot mixture screw more than two turn
The point is that I don't need to back out the pilot screw, because it slows down. The highest rpm is on the maximum turning in (minus 2,5 turns - there is a plateau).
So I can suggest slow jet it is too large 8O. It can explain why choke doesn't work - mixture is to rich by itself.
But !!!
1) The engine won't start whatsoever without a throttle
2) The plug is almost pristine white.
It baffles me 8O [/b][/i]

[Weldangrind]

The pilot mixture screw is in the ideal spot when you can crack the throttle and not have the engine stumble. If the bike won't start without throttle, that tells me that the slow jet is too small. Your white plug confirms that it's not getting enough fuel.

[akvilonBrown]

Yeah, cracking the throttle may cause engine go dead, especially when not fully warm, regardless of pilot screw positions.

So playing with various slow jets seems most practical idea. From now it will take long time to figure out how to ship jets, but eventually I will post the results.
Thank you, Weldangrind, for quick response.

[saboor73]

Sorry guys for bring up old thread but in need of serious help can any one tell me if this is correct needle for miken pz27 if not can anyone please share a pic of correct carb needle
http://g02.a.alicdn.com/kf/HTB1gDBPIXXXXXa4XXXXq6xXFXXXe/Needle-valve-of-CG125-CG150-CG200-carburetor.jpg_640x640.jpg
http://g01.a.alicdn.com/kf/HTB17qpGIXXXXXcoXpXXq6xXFXXX5/Needle-valve-of-CG125-CG150-CG200-carburetor.jpg_640x640.jpg

[saboor73]

Sorry guys for bring up old thread but in need of serious help can any one tell me if this is correct needle for miken pz27 if not can anyone please share a pic of correct carb needle
http://g02.a.alicdn.com/kf/HTB1gDBPIXXXXXa4XXXXq6xXFXXXe/Needle-valve-of-CG125-CG150-CG200-carburetor.jpg_640x640.jpg
http://g01.a.alicdn.com/kf/HTB17qpGIXXXXXcoXpXXq6xXFXXX5/Needle-valve-of-CG125-CG150-CG200-carburetor.jpg_640x640.jpg
Any one