ZRX1200 Carb Conversion

[IanDMacDonald]

Gonna take a small break on this. I ordered new carb intake manifolds (upon inspection, there was nothing wrong with the ones I had on, other than external cracking), ANOTHER set of steels, frictions, and springs (cheap eBay set), along with a clutch cover gasket to see if I can figure out what's going on with the clutch. I have the carbs on the bench ready to go back on.

Bonz- I have not gone up yet on the Pilots (again). I'm at 40's right now (started with 38's), and trying 3 turns out (but they're starting to feel loose). I did drop the clip one position to see what it'll do. I do have 42 and 45 pilots to try.

If all works out, my next steps are figuring out how to secure the airbox in place and figuring out the throttle cable. I did order another XJ750 cable (what I'm using currently, as I have SuperBike bars).

I was tempted to drill and weld O2 bungs into the headers, but this is OE exhaust in perfect condition, so I did not want to risk damaging the exhaust. Trial and error. I'm running out of time.

[Bonz]

Sounds good. Good call on going up on the pilots if three or three and a half turn starts to feel loose. No choice but to do that. 40's will make a difference in cruise mixture. 40p's flow 11% more fuel vs 38's. Since that's one of the main contributors to cruise, you should see some improvement with those on top of going richer on the clip.

[Bonz]

Sounds good.

[IanDMacDonald]

Excellent information. The bike is 2.5 turns on the pilots, if it's idling well, my move would be to leave those alone for the moment. Definitely a good next change is going to the fourth clip position.

The AFR gauge change at idle on the ZRX 1200 shows .5 to .7 of a point richer or leaner with a half turn on the pilots. For what it's worth I've run 40 and 38 pilots in those carbs, and the change amount is basically the same with a half turn.

My thought ia a full turn on the pilots and a clip position richer at the same time would take a bigger swing at it then may be expected.

Main thing is you know what you're looking for on the plugs. If it's telling you to do a full turn along with the clip position adjustment, by means go with what it's telling you. Either you undo some richening because it was too big of a swing, or if you don't adjust as much and it's not enough, you're doing another adjustment either way. Kind of the beauty of doing all this isn't it, lol.

Yeah, I was looking super-lean, at 2.5 turns on the A/F screws, and 3rd clip position down from the top. I think I'll go half a turn out, as the A/F screws are starting to feel loose at 3 turns. Anything more, and I'd be concerned. And, I'm dropping the clip to the #4 position from the top.

[Bonz]

Excellent information. The bike is 2.5 turns on the pilots, if it's idling well, my move would be to leave those alone for the moment. Definitely a good next change is going to the fourth clip position.

The AFR gauge change at idle on the ZRX 1200 shows .5 to .7 of a point richer or leaner with a half turn on the pilots. For what it's worth I've run 40 and 38 pilots in those carbs, and the change amount is basically the same with a half turn.

My thought ia a full turn on the pilots and a clip position richer at the same time would take a bigger swing at it then may be expected.

Main thing is you know what you're looking for on the plugs. If it's telling you to do a full turn along with the clip position adjustment, by means go with what it's telling you. Either you undo some richening because it was too big of a swing, or if you don't adjust as much and it's not enough, you're doing another adjustment either way. Kind of the beauty of doing all this isn't it, lol.

[IanDMacDonald]

Yes and no going up on the mains.
-What position/groove is the clip on the needle.
- How does it pull/feel once you're up on the main accelerating hard above 6,000 or 7,000 rpm. Reading your previous post today, appears it's running well throughout the power band.

If it pulls good at high RPM acceleration, richen up the needle first, IMO/IME.

I think I'm in the 3rd position down from the top. From memory of your previous post, I want to lower the clip (#4 slot down from the top) to richen it.

I think I'll go one more turn on the A/F screw, and drop the clip, and report back.

[Bonz]

Yes and no going up on the mains.
-What position/groove is the clip on the needle.
- How does it pull/feel once you're up on the main accelerating hard above 6,000 or 7,000 rpm. Reading your previous post today, appears it's running well throughout the power band.

If it pulls good at high RPM acceleration, richen up the needle first, IMO/IME.

[IanDMacDonald]

Ian, is the cable streching upon use ? Maybe go an 1/8 turn at the arm ?

Nah. Brand new cable. Not a cable issue.

On another note: I pulled the plugs, and certainly FAR from running rich. Very lean. I'm at 140 mains. I may need to go up.

[Schming]

Ian, is the cable streching upon use ? Maybe go an 1/8 turn at the arm ?

[IanDMacDonald]

Wouldn't adding a steel make it worse?

I'm not sure, Mike. I DO know that originally upon acquiring the bike, the owner had an extra steel in there. All I know is that I cannot adjust this thing to get it from lurching, when putting it into gear.

[Radioguylogs]

Wouldn't adding a steel make it worse?

[IanDMacDonald]

Alright: Took it for a quick ride this morning before I get deep into work meetings. Runs well, pulls just as strong in all revs without bogging. Just the same as with the Mikuni's. I'll take it for another quick ride at noon to allow more color to develop on the plugs, then pull the plugs this afternoon to see where it's at.

On another note: I was able to free all butterfly screws on the Mikuni's, and will order new seals, despite them all looking okay. I know Len sells them, but they're cheaper through Partzilla. I also think I'm going to order new intake manifold boots from Mikes. I tested them for leaks and did not find any, but I'd rather play it safe.

The next issue to deal with that I'm constantly chasing is the clutch: I cannot get it adjusted properly to save my life. New steels and frictions, and my Barnett springs are still in spec. Throwout adjusted per the manual (1/4 turn). When I drop it in gear, it lurches and stalls. I've filed down the basket to ensure the frictions are not grabbing. The only thing I have left in my toolbox to try is adding steel and hoping that helps.

Thoughts?

[Bonz]

Awesome. Keep those updates coming!

[IanDMacDonald]

I mispoke. Yeah, I upped the sizes from Keihin 38's to 40's. I kept the 140 Keihins main jets in. I'm at 2.5 turns out. I have the carbs "synced", but not technically. I synced 1 to 2, and 4-3, but when I attempted to sync 2 to 3, I had a hanging idle. So, I left the two banks unsynced to keep the idle from hanging. I'm letting the engine cool so I can pull the plugs and see where I'm at for fuel mixture. From there, I'll attach the tank and tank it for a spin and see what everything else is doing.

[Bonz]

138 and 140 are main jet sizes, you're going to increase the main jet size as well? Or were you meaning 38's to 40's on pilots.