Pz19

I recently bought a PZ19 carb for my little 48 and wanted to share some experience I've had with it.

A couple notes about the coolness of this carb.
a) It has an actual o-ring seal. No more leaking intake bs!
b) It has a dedicated idle circuit. The NT carb relies on the main jet for all aspects of fuel delivery, which can make the idle pretty iffy.
c) cable operated choke!
d) The fuel bowl is HUGE! You will not have any fuel starvation issues. It stores so much fuel in the bowl, I forgot to turn the gas on and made it over 2 miles before I noticed. It didn't die on me, I just happened to look down.



Just looking at it, you can tell it's a monster, compared to the standard NT carb. The NT has a 14mm diameter throat, and this one's 19mm. That doesn't sound like a lot, but think about how much more cross sectional area that is! I also checked the jet size before getting too far. It's a size 69. My current NT was running a 68. We'll have to see what it does? If anyone can explain how different size carbs compare with the same size engine and jet, that would be great.

First thing to know is that it's not just a direct swap-on carb. You will have to do (or hire someone) some fabrication. The flanges are very different.



So I got to fabbin' and noticed that while the intake port is a rounded off rectangle, the intake manifold and gasket is a 14mm circle. I fixed the gasket with a gasket punch kit (made the inlet a little more squarish) and I tossed the old Z kinked intake in the parts bin. Nothing there to reuse.



A little massaging here and there and it fit pretty well!



I got it all welded up and I spent some time with a file and dremel stones, smoothing out the inside. I probably spent too long on that part honestly. I mean, I was able to milk 43mph out of it with the stock NT and the z-kink manifold, I may be putting too much effort in to this lol.

I did notice that the bowl is not level with the ground. Not a big deal though. I put it to the test overnight with the fuel valve on. Not a single drip.

So, what's the final word? I'm not too sure. I got the fabrication done Saturday night. I went for a ride and got 20 feet before had to go home and get my winter motorcycle gear on.

Round 2 and I pulled the starter cord, and it fired right up and purred at idle. A nice, strong idle. I hopped on and pulled on the throttle and WOW it had torque. Up to a certain speed (felt a little slower) but the midrange really improved a lot.

The next 2 days I got maybe 15 minutes total to tinker. I thought that it had only bogged on me, and not 4-stroked. So I went up a jet size larger. It warmed up a lot since the day before, so no full-face helmet this time. I went out and did a full throttle run, only to experience crazy amounts of 4 stroking. So the 68 jet is too much, maybe it did 4 stroke with the 69 jet and I couldn't hear it with the full face helmet on?

So now this is where I stand. The idle and midrange are FANTASTIC! I just have to get the main jet right and keep taking it for WOT runs to see how things work out. And I'll also be grabbing up an air filter for it soon too. My CDI is getting soaked from the 2stroke spray

I'm a little confused and concerned about this now. I seemed to have gotten the main jet right on the money this morning, maybe still a little rich, but for the most part it was doing well. I went out to Lowes for a scavenging adventure and found what I wanted to use as an air cleaner. It's a small piece of sink drain, about 1-3/8" ID. It fits perfectly over the carb, so all I needed to do was drill a couple holes and add some set screws, then affix the foam air cleaner inside. Overall, it was very inexpensive and looks way cool. It's also much less restrictive (and by that I mean there's no torturous path to the carb like the NT carb cleaner).

Anyway, I get the cleaner on and go for a spin and the 4 stroking is back, worse than before. I pulled the jet and decided to jump down 2 sizes, and it is much better, but still 4 stroking and smoking bad.

I don't get it!!! I was using a size 68 jet on the NT with great success, but on the bigger carb I'm still too rich at 72?

Can someone explain this please?

Yeah man. I get that. I expected a little restriction. But why (with a bigger carb, a bigger, less restrictive air cleaner, a less restrictive and larger diameter intake manifold, and a properly matched gasket) is it using a smaller jet and now not revving as high?

OK, so I got the jet down to a 0.023" and it was doing pretty good... then it bogged down real bad. I had to hold the choke on the whole way home (I don't have the cable operator yet). Once I got home, I realized my air cleaner was gone. Well, no more tuning tonight I guess.

The air filter was the foam sheet out of the NT carb. The housing it was in was literally a piece of 1-3/8" sink drain pipe. Straight shot in, through a piece of 1/4" thick foam.

I think what I'm getting at is that it shouldn't have been that restrictive.

I just ordered a pz16. I want to see what it'll do comparatively. It shows up in 2 days. Thanks Amazon!

The PZ16 seems like it will be the better option.


However...


It has to be mounted perfectly level it seems. I've re jetted again and again, and still seem to have lean and rich moments. Then I noticed the fuel spraying out of the overflow. That clued me in to float level issues. I bent the float down some to compensate, but still not perfect.

I really do think this carb may have the most potential, but I'm not sure it will work unless I can figure out how to get it completely level. I may need to have it hang off the side 90 degrees so I can have enough room for everything. I guess I'll hust have to try?