ZRX1200 Carb Conversion

[Bonz]

For sure I don't want to be the one to say pilots and it's the mains or say mains and it's pilots. Lol.

Three turns out of the pilot says that's pretty good for idle, Going up a size in pilots would probably mean two turns out total on the new screw setting more or less.

If you feel it pulls good up top, try richening up the needle a half position at a time. If you are at three notches down from the top, put a washer under the clip to make it 3.5. Or however you would arrange the clip and washer to get a half position based on your current setting.

I've discovered two stages to barely cracked throttle according to my wrist and the AFR gauge. Barely barely cracked which is still the pilot system, and then barely cracked past that which starts to bring the needle up out of the main ever so slightly. I tend to spend more time at the second stage of barely cracked throttle and was leaner than I wanted to be. A half position on the needle got it better without richening everything else up too much.

Thanks for asking for the advice, I hope it gets things richened up.

[IanDMacDonald]

Here's what I'm thinking: (3) turns out for the Keihins seems too far. So, I'm going to take the pilots out to 42's from 40's. Then, the Main's from 140's to 142's. I think that may be the perfect mix. Ideally, I leave the needles in the middle position.

[Bonz]

That's as good of a plan as any. Three turns out on ZRX (Keihin) carburetors is not too many, IMO. Unless you feel like the screws are going to rattle out so to speak. 2.5-3 turns is a common setup with most aftermarket jet kits running those carburetors on the ZRX.

Main thing is you want to richen it up, and both of those will accomplish it from opposite ends of the operational spectrum. No harm running a bit rich versus the alternative.

[IanDMacDonald]

That's as good of a plan as any. Three turns out on ZRX (Keihin) carburetors is not too many, IMO. Unless you feel like the screws are going to rattle out so to speak. 2.5-3 turns is a common setup with most aftermarket jet kits running those carburetors on the ZRX.

Main thing is you want to richen it up, and both of those will accomplish it from opposite ends of the operational spectrum. No harm running a bit rich versus the alternative.

If I remember correctly, anything past 3.5 turns on the mixture screws, and the screws felt loose from lack of thread engagement. So, going up in the pilots will probs help. I have to make a trip to Chicago tomorrow, and Atlanta on Wednesday, so I'll wait for the mains to come before slapping the carbs back on. I ordered two more sets of plugs to test with.

[Bonz]

Looking forward to the next time you can work on it. Thanks for all the updates.

[jetmechmarty]

Another twist. To richen less than a jet size, go down a size on the air jet.

[IanDMacDonald]

Another twist. To richen less than a jet size, go down a size on the air jet.

The one jet most of us never touch on these.

Yet, on my Volkswagen Weber carbs, the air correction jet is the difference between a happy engine & not.

[Bonz]

ZRX carburetors don't have adjustable air jets. Air jets are pressed in place.

It's a good idea if it was something that could be done.