ZRX1200 Carb Conversion

[IanDMacDonald]

TADracer I noticed you left your ACV tubing in-place. Can I delete the tubing, and cap the ACV ports?

[Bonz]

I have Keihin original mains 128, 130, 145, 150, and larger. That brackets the sizes you're looking for, but if those would help you, me know.

I've adapted Keihin CVK40s from the ZX11/ZZR1200 to the ZRX and they use the same jet styles as the stock ZRX 36mm Keihin carbs. Bought lots of jets over the course of the trial and error. Finally spent money on an air fuel ratio gauge, it would have saved me more money in jets than I bought the gauge for lol.

Rocky Mountain ATV sells the main jets individually for $7.99 a piece. Look under the carbureted Kawasaki KLR 650 and it's the same jets. The 393 series. I looked and they're the same back to at least the 2000 model year KLR 650.

N424-25B is the pilot jet, same ones for KLR 650 will function there as well. Rocky Mountain ATV has those in 35, 38, 40 and larger. Shouldn't need bigger than a 35. $7.99 piece as well.

If the ACV's are in place, no harm no foul. If want to cap them, no harm no foul there either. Might get a bit more popping on decel.

You will like the needle valve seats, they are pressed into the ZRX carbs don't have to worry about those o-rings.

[IanDMacDonald]

I have Keihin original mains 128, 130, 145, 150, and larger. That brackets the sizes you're looking for, but if those would help you, me know.

I've adapted Keihin CVK40s from the ZX11/ZZR1200 to the ZRX and they use the same jet styles as the stock ZRX 36mm Keihin carbs. Bought lots of jets over the course of the trial and error. Finally spent money on an air fuel ratio gauge, it would have saved me more money in jets than I bought the gauge for lol.

Rocky Mountain ATV sells the main jets individually for $7.99 a piece. Look under the carbureted Kawasaki KLR 650 and it's the same jets. The 393 series. I looked and they're the same back to at least the 2000 model year KLR 650.

N424-25B is the pilot jet, same ones for KLR 650 will function there as well. Rocky Mountain ATV has those in 35, 38, 40 and larger. Shouldn't need bigger than a 35. $7.99 piece as well.

If the ACV's are in place, no harm no foul. If want to cap them, no harm no foul there either. Might get a bit more popping on decel.

You will like the needle valve seats, they are pressed into the ZRX carbs don't have to worry about those o-rings.

I appreciate that very much. I ultrasonically cleaned the carbs. I just spent $150 at MikesXS for pilots and mains (38/40/42/45 pilots, 135/138/140 mains). I DO have two A/F gauges with an O2 sensor, but I'm using the original exhaust on the XS, and would feel bad cutting a hole into it for the bung. I ordered an o-ring kit from Kwick, along with the block-off plate for the K-TRIC. I did forget to buy o-rings for the ACVs. I'll circle back to that, and emailed Pete from Kwick, to see if he could add it to my order.

[Bonz]

You've got a great source for parts for the ZRX from KWICK. That's his forum name on the zrxoa.org. His company name is ELS, for "Expensive Lightweight Stuff" as he makes and sells lightweight ZRX parts to replace stock parts, ignition advance rotors, pod adapters, et al, as well as sells OEM ZRX parts. He's a good guy to support with buying some parts. You probably saw that if you've been on his site.

My instinct is you are in good shape with the main sizes. Be surprised if you go larger than 38 on the pilot. 35 is stock with those carbs when on the ZRX.

Dialing the ZRX in with the AFR gauge in the last couple weeks, the difference between a 38 pilot and a 40 pilot in the CVK40 carbs is huge when it comes to the fuel it provides. Pilots provide a lot more fuel than folks think.

Find the main that gives the best feel at high rpm as I totally understand not wanting to put a bung in those exhaust pipes. Then dial in the needles for WOT and roll on acceleration from low RPM and in the mid-range and also the feel at cruise. Then start looking where you are on pilot screw turns. That will determine where to ultimately end up with the pilot size.

As soon as the bike will run and hold a steady idle sync the carbs. That's going to make the whole process easier. A sync that is off will make you chase other stuff 'til you are blue in the face.

Keep posting, I threatened to do this when I had my SG, but never did. Looking forward to following!

[IanDMacDonald]

You've got a great source for parts for the ZRX from KWICK. That's his forum name on the zrxoa.org. His company name is ELS, for "Expensive Lightweight Stuff" as he makes and sells lightweight ZRX parts to replace stock parts, ignition advance rotors, pod adapters, et al, as well as sells OEM ZRX parts. He's a good guy to support with buying some parts. You probably seen that if you've been on his site.

My instinct is you are in good shape with the main sizes. Be surprised if you go larger than 38 on the pilot. 35 is stock with those carbs when on the ZRX.

Dialing the ZRX in with the AFR gauge in the last couple weeks, the difference between a 38 pilot and a 40 pilot in the CVK40 carbs is huge when it comes to the fuel it provides. Pilots provide a lot more fuel than folks think.

Find the main that gives the best feel at high rpm as I totally understand not wanting to put a bung in those exhaust pipes. Then dial in the needles for WOT and roll on acceleration from low RPM and in the mid-range and also the feel at cruise. Then start looking where you are on pilot screw turns. That will determine where to ultimately end up with the pilot size.

As soon as the bike will run and hold a steady idle sync the carbs. That's going to make the whole process easier. A sync that is off will make you chase other stuff 'til you are blue in the face.

Keep posting, I threatened to do this when I had my SG, but never did. Looking forward to following!

Hey, Bonz- The ZRX carbs came with shimmed needles with the clip at the lowest setting, and two washer shims above it. Do you have an idea of the best clip position to start with? And, should I use both washer shims?

[Bonz]

A needle with adjustable clip says an aftermarket jet kit is installed. Pull the bowls and see what main jets are in there. If those were jetted for pods, you may already have 130s or 135s in the carburetors. There were basically four main players in the aftermarket jet kits for the ZRX.

If you would take a picture of a needle I can give you an idea who's needles are in there and helps to know where to start.

Clarify: Shimmed needles with clip in the lowest position. Is there a shim under each clip, or only the two shims on top of each needle? It's a minor detail, regardless the clip in the lowest position is as rich as it can get on the needle.

The two shims on top are to take up the space between the top of the aftermarket needle and the bottom of the plastic spider that sits on top of it. It makes no difference in the jetting as that's controlled by the underside of the clip. Some guys swear you need them, other people who are in the know that I've talked to you say it makes no difference. I personally don't run them on top of the needles. However if you have them, leave them on top unless you're going to use one of them to adjust to half clip position.

Typically the clip is put in the middle position, middle of the road to start, on most needles it is the third one down. There's one brand of needle I believe that has six positions, you'd still want to be in the third one down.

I'm probably as curious as you are as to what is in those carburetors already. It will be real helpful to know as much as we can.