ZRX1200 Carb Conversion

[Bonz]

Best of luck tracing the oil leak, that's maddening at the least, and will drive you insane in the grand scheme.

I've reused head gaskets on the ZRX 1200 a time or two, whatever the copper head gasket spray is that recoats the head gasket, has never let me down. I would trust that more than RTV. RTV works great on valve cover gaskets or base gaskets that don't see much pressure. Head gaskets get a **** ton of pressure, copper head gasket spray is a better option.

[IanDMacDonald]

Okay. Put the 142 Mains, and 42 Pilots in. 2 turns out on the mixture screws. Took it for a 5-mile ride. Runs extremely well, pulls strong. I'll pull the ppugs in the morning to see where I'm at for a tune. It would not surprise me if I was still lean.

On another note: I still have another oil leak. I heard it when I parked the bike, and saw oil dripping on the exhaust. I'll attempt to find it tomorrow after I pull the plugs. If it's NOT the head gasket, my only guess is the ACCT, but I have that RTV'd with a gasket, so not sure.

[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.

[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.

[jetmechmarty]

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

[Bonz]

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

[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]

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]

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]

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]

If you run into a hard time finding the 42's, I have a set of four that'll work if going up on the mains doesn't do it.

I have 42's and 45's. Do you think it's wise to go up with BOTH pilots and mains at the same time? From memory, I think I'm at 3 turns out on the mixture screws.

[Bonz]

If you run into a hard time finding the 42's, I have a set of four that'll work if going up on the mains doesn't do it.

[IanDMacDonald]

I just ordered some 142's & 145's from MIke's, as I think I'm running 140's at the moment. I might go up in the pilots as well.

[IanDMacDonald]

Yeah, I think I'm running 40's on the pilot jets right now. I think I need to go up.

[Bonz]

When they are really lean like that, it's not a bad thing to go up one main jet size on those cylinders or up one size on the pilot Jets on those cylinders. If you're doing mostly cruising around pilot jets make that difference in plug color in my experience.

Made a change on the ZRX last night before a ride up to Cripple Creek for a Veterans appreciation motorcycle event today.

38 Pilots even with 3.0 needle clip position, light throttle cruise with the air fuel ratio gauge was in the high 13:1 to high 14:1 consistently and would blip to the lower 15's. No bueno for a carbureted bike in my opinion.

Went to 40's on the pilots, light throttle cruise AFR was back in the low - high 13's mostly, with a few times in the 14s but not passed stoichiometric of 14.7. Never saw 15's. Along with that I went a half position leaner on the clip position. That shows, to me anyway, the pilot jets are what are keeping those plugs looking lean because the air fuel ratio at cruising richened up even when I made the needle position leaner.