Newb with Keihin CR29 Specials

Just joined and just bought a very nice and clean 77KZ900. Specifics are in my sig.

The issue I'm having is that these carbs don't play nice at low speed, low RPM....like cruising through my neighborhood. Don't know what jetting sizes are in it as the PO had someone build the motor and install these carbs, I'm assuming with the mods in mind.

I have the original Mikuni VM26's that I'm going to go through and rebuild regardless. My question is, will these Keihin CR's be jumpy at low speeds regardless of what jet sizes I use? I mean, I fully understand that these are race carbs and were more meant for full WOT majority of the time. I won't know exactly what's in them until I get some time to pull the CR's off. Anyone with similar mods running these carbs with no issues? What jets are you running? I would like to keep these obviously, but I want a smoother running bike all around and if these just aren't meant for the street, I'll just use the stockers.

Thanks in advance!

Hi BoomFist.
I put a new set of CR29's on my 810cc Z650 and they worked really well but did take a few jet changes and a needle change to get right. Cold idle was 700rpm, warmed up it was 1000rpm. Engine could rev well past redline. The choke only worked in real cold weather, didn't use it otherwise.
You can improve low range performance on those carbs with a Yoshimura MJN kit but they are expensive.
Providing there are no underlying issues with your motor you should be able to get the CR's tuned in. You have a couple hundred more cc's than me so I may be wrong.
Maybe another member can share his knowledge of these carbs on the larger motor.

Thanks for your input stone. I'm hoping someone with a more similar set up chimes in. I'd like to get a baseline jet size in mind so when I pull them off the bike I can have them ready to install depending on what's already in there.

I'd check they are in sync and readjust idle mixture screws if needed until you get some info on jetting.
It's easy and does make a big difference.
I synchronised mine with the top covers on, only removing the cover to adjust the slide.
For mixtures, set the idle higher than normal. Turn the screws in or out to get the highest rpm. If they're more than two turns out from seated you'll need larger slow/pilot jets. Alternatively use a colortune if you can get your hands on one.
Recheck the sync after adjusting pilots.
Out of the box these carbs are jetted on the rich side.

69.46.28.106/forum/3-carburetor/342026-m...l=component&type=raw

Thanks so much for that link!

It makes me feel a little better to hear that a lot of people like these carbs with a few tweaks from factory. So, my next step is to pull them to see what size jets are in them. I'll buy a few different sizes that were recommended in that thread then check the float levels (after I build a carb holder from another thread I just read! Which is awesome!), then I'll reinstall them and sync them up after I buy a synchronizer.

Much appreciated guys! Thank you!

As the CR's were originally designed for racing, jets and needles can be changed without pulling the carbs. The main jets can be removed after undoing the drain plug, the needles can be removed after removing the top covers and the pilots can be removed after dropping the bowls. Unfortunately removing and installing the throttle cables can be a bit of a pain.

Unfortunately my riding season is done for this year. I was hoping to be able to ride at least a handful more times before I had to park her for the winter.

So, part of the reason I'm going to just yank them off is so I can inspect the inside and clean it up so it's fresh for next spring. I had a fuel leak on the right most side carb and am suspecting a stuck float. With the PO owner admitting to only riding it once this season, I have a feeling there's some build up of some sort.

Thanks for your input man.

Once you get them dialed in, you'll witness the difference....
As mentioned, they come from factory RICH....

Phoenix AZ @ 1200 elevation, weather 3/4 of year 90 to 115F (Yeah I know, feakin hot)
Mains @ 112
Pilot @ 55, could go down to 52 but being so hot here, rather it'd be a tad on the rich side then lean.
Needle, YY8 clip position 4..... I change clip position between cold and extreme hot 90F plus temps...

You're the man OMR! I saved all of that info.

So, I got to pull the carbs and dig into 1 of them. Didn't take it fully apart, but I got to see I'm running 120 mains and the needle position at 4. Don't know which slow jets yet.

OMR, with your 112 main and 55 pilot, are you happy with the results? Is it jumpy at low speeds like I was describing? Where's a good place to buy a variety of main and pilot jets?

For Jets... You'll need to find a SUDCO distributor or try here for which I've found pretty much all I needed... jetsrus.com/

"112 main and 55 pilot, are you happy with the results?"
Yep.... She'll run a tad on the rich side (plugs slightly sooted) and she'll purr to life easily, nice idle 900-1000 rpm.

With 52 pilots & YY9 needle w/ clip position 3, found pending time of year and heat index spark plugs are more gray in color than suit brown/black but found she'd jump around in idle where I'd raise the idle to ~ 1200-1300 to compensate.

You'll also find where these carbs don't need choke.... Pending your environmental conditions, raise choke ever so slightly and I mean slightly ~1/8th to 1/4" max is all that is required.

Thanks again for the link!

So I'm currently running a 65 slow jet and a 120 Main.

I want my set up to be the most ideal street riding setup. I want to be slightly rich as well, so I think I'll be mimicking your setup OMR. Might go ahead and order a few other jets to play with too. Leave the needle position alone, correct??