ZRX1200 Carb Conversion

[IanDMacDonald]

For what it's worth: I did indeed do that to get them to seat, when first installing the butterflies (as they were not centered). I'm ready to move on back to the ZRX carbs.

[bikerphil]

Blue Loctite on the throttle plate screws throws loosening of the plates out the window...

With that said, I like the idea of putting them in lightly snug and snapping them shut a few times. Could be accomplished in the minutes after using Loctite before it begins to cure. Then snug them down and they are good for eternity.

The first time I changed throttle seals, I put the plate screws in with blue locktite, not knowing about the alignment problem. Sure enough there was a hanging idle. If I forced the linkage closed, the idle would come down. I separated the bank and I was able to break the screws loose without too much effort using a JIS serrated tip screwdriver. I can't recall if I used a propane torch or not to heat the screws, but I did get them loose and was able to snap the throttle closed on each individual carb and reset the plates. That indeed was the problem. Carefully using localized heat on the screws shouldn't be an issue regarding the health of the seals as IIRC, the shaft is made of aluminum and will not hold heat for as long as steel would. I wish I remembered this earlier so I could have tipped Ian about this.

[Bonz]

Blue Loctite on the throttle plate screws throws loosening of the plates out the window...

With that said, I like the idea of putting them in lightly snug and snapping them shut a few times. Could be accomplished in the minutes after using Loctite before it begins to cure. Then snug them down and they are good for eternity.

[IanDMacDonald]

Something that may have been overlooked on the Mikuni is snapping the throttle shut a few times with the butterfly shaft screws loose to properly seat/align all the plates. Then tighten them. Otherwise the throttle plates will probably hang up.

Lol. No going back with those screws. I blue locktited them and peened them.

[bikerphil]

Something that may have been overlooked on the Mikuni is snapping the throttle shut a few times with the butterfly shaft screws loose to properly seat/align all the plates. Then tighten them. Otherwise the throttle plates will probably hang up.

[Bonz]

Hanging idle is a bummer. ZRX carbs will be a good experience once everything is dialed in, IMO. That's the fun for me, more "modern" carbs vs not made in the same century and making them work like it should. XS 1100 carbs 1970's- early1980's. ZRX1100/1200 carbs 1990's into mid-2000's.

Did it with ZX11/ZZR1200 carbs on the ZRX. Downdraft carbs from a ram air motcycle adapted to work on a side draft head. Noticeable power increase on the dyno, 5-7 hp, and 2-3 mpg upgrade from stock.

[IanDMacDonald]

Well, even with the butterfly shaft seals replaced + intake boots, that hanging idle is still present with the Mikuni's. It kinda sucks, as that head being destroyed was for nothing.

I have a leak on the front end, which is more than likely coming from the ACCT. I'll check the torque on the head bolts to ensure it's not from the base gasket. I dusted down the bike with AP flour to see if I could find it, and couldn't.

I'm going to start over with the ZRX carbs.

[bikerphil]

Wow, what an ordeal to have this happen when doing this carb mod, good that it's back running.

[IanDMacDonald]

Aight. Got it started. No issues. Back to square one with the carbs. Will re-time the bike, then tune with the Mikuni's, first. If it won't hold an idle, I'll go back to the ZRX carbs.

[IanDMacDonald]

Zee head is on. Taking a small coffee break, then cam install. So far, so good.

[IanDMacDonald]

Well, back to the grind. I have the replacement head painted, new valve stem seals, valve lash checked, threaded holes clean, and ready to install with a new head and valve cover gasket.

I decided to start the process tomorrow, as I did not want to start and not finish today.

From there, I'll install the old carbs first and see where I'm at as far as holding an idle.

[IanDMacDonald]

Here's hoping it ran well for the short jaunt! Looking forward to hearing about the plug check.

Interesting. Pulled the old plugs, and put new one's in. Went for a 20-mile ride at various speeds. Cyl.'s 3&4 have rich plugs, but Cyl. 1&2 are lean. Either I need to go up on the mains, or something.

I did put the old carb bank back together. I'm tempted to put them back on and see if the vacuum leak is gone.

[Bonz]

Here's hoping it ran well for the short jaunt! Looking forward to hearing about the plug check.

[IanDMacDonald]

Okay, got the carbs back in, and the bike definitely likes the 40 pilots. Idles well. I took it for a short jaunt, but it started raining. I want to put some more gas in the tank and take it for a longer ride with new plugs in, to see where I'm at.

From there, I'll have to pull the tank again and figure out the throttle cable and airbox mount.

[Bonz]

Thanks for sharing the update on the carb jetting. I didn't realize you were already at 40's. Sounds like you're turning and burning, making the changes to dial this in. Sorry about the clutch, that's frustrating.