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I could use some input from those of you running the CR's, please. Mine are newly installed on my 836 bike. I've done a lot of carburretor tuning over the years, but this set-up has me puzzled.

1. Keihin Pz27 Carburetor Tuning
2. Racing Carburetor Tuning

They are fresh out of the box and have the K&N's installed that are sold with them. I started it up and rode it Saturday for the first time since the rods, studs, and chain upgrades. I only rode it 10 miles as rain was going to happen - just wasnt sure when. Yesterday I rode some more to check for leaks and bring it up to temps, then to check for idle adjustments at the air screw and idle speed. rode a little better.Here is the deal -These only have about a 1/3 throttle turn from fully closed to fully opened, so metering the throttle is quite a bit more delicate than stock. The carbs will not allow any 'quick' throttle opening. If you twist the throttle open at low, middle, or anywhere before 7,000 - the huge air signal is dry and therefor causes the motor to die momentarily.

If you twist it open at 7,000, you get a few blubbers (rich), but it quickly goes into it's hardest and most exciting pull of it's range. If these transitions in throttle are made moderately - then it never has a dead spot, lean spit, or rich blubbering. This makes me thing the jetting is ok.

I also measured cylinder head temps throughout the ride to confirm I wasn't melting something. Normally a problem like this - I'd raise the needle clip to cure what would be a dead spot in the middle and a lean spit, then drop the mains by 1 size to cure a rich condition that persisted regardless of application. Here I can get low, middle, high perfomnace from each circuit as -is, but you can't open the throttle before the engine can use it.

On a regular carb - I'd never be able to transition through it.I would say an acellerator pump is designed to cure such problems on autos. They squirt about 5cc of raw gas into the intake manifold when the pedal is floored to help cure the exact symptom.

Am I missing something about tuniing the CR's or am I finding something that is to be lived with and expected? Or is there a cure?Thanks,Gordon. Jim, thanks for the confirmation of jetting. With the exception of the 230 air-jet, yours has all of the jetting of a 33mm.

I would think they all use the same carb, just a larger bore in the venturi - the outside dimensions would be the same. I know Mike's are 31's and from the outside look identical.By the way, mine are 120 mains, 60 pilots, 250 air jet, Y8 needle in the 4th position, air screw likes 1/2 turn out - no more else it lean spits.I called and spoke with Sudco. They gave me some information - Some I didn't want to hear 1) They haven't yet written any instructions for tuning nor put together a tuning guide for the Keihin carburettors. 2) My result is about right for a performance carb. It can't react suddenly to change and they have developed the FCR's with a fuel pump to address this problem.

I should replace my throttle or transition slower when going from part to full throttle as signal will be lost.I re-read my Sudco Mikuni tuning manual this weekend and I'm not going to follow it's instruction either. It states to run the main jet giving the highest top speed in top gear - then go up 1 size for safety. I don't have the nads to go full-out.

ILbikes,I am guessing here, but the problems you are experiencing may be caused by simple misconfigurations.1. From your photo, it looks like your CR carbs are aligned at a slight downward angle. I believe it is necessary to have your carbs as close to perfectly level as possible otherwise, your float level will not be correct.2. Your throttle cables must be the incorrect size. You should have much more than 1/3 of turn on your throttle. Your CRs are problematic because they are not fully closing or opening.3. I noticed that you have the Dyna 2000 ignition.

Be sure that you have the timing correct and the advance curve set correctly.Sparty. Art, actually the venturis are in perfect alignment with the intake boots and manifolds and are within the tolerance for lean angle. I've got huge Mikunis on my H2's that are much more extreme. As the floats are round, they will act upon the float valve at the same time as if level. I do lose some closing pressure since the lift is not entirely vertical, but still plenty of pressure to seal the fuel valve.The timing is spot-on at 36 degrees full advance for 1/4 and 2/3, so both pick-ups are perfect. The rev limiter is set on 11,000 and the curve on # 4 per spec.

For two valve applications and normal compression. As for throttle, I'm using a OEM grip, case, and cable system for the K4. Some mods were necessary for the cable installation, but I am getting full closure and full opening and the proper open/close tension. I checked those performances before ever adjusting the push/pull cables or installing the filters.

Keihin Pz27 Carburetor Tuning

These just don't transition quickly and I'm surprised by that gap I've got when these are quickl opened.Thanks for the input. I don't mean to sound ungrateful - it's just that I've been around the block a time or two.

These CR's are not the Mikunis I'm used to dealing with.Regards,Gordon.

Shop by CategoryShop by MakeInspirationCan't Find What You're Looking For?or Call us at 727-386-9735shop by BrandTell us about your build!Share your photos and story with other Speed Freaks like you.categoriesLatest PostIn 1967, Honda decided to throw its hat in the 'police motorcycle' ring. Using the ever-popular CB450 as a template, a few touches were added to make this new venture a feasible service motorcycle. Patrol lights were accompanied by a siren. A large, circular speedometer displayed speed ranges of each gear and had a 'locking' needle that was used to determine speeding vehicles back in the pre-radar days. The lucky owner of this rarity is none other than DCC customer Glenn Moss. Color/Finish: Raw MetalDimensions: N/AMaterial: SteelFits: CB750 1969-76Please allow for additional time while carburetor internals are set for indicated bike.All CR carbs are pre-jetted with the assumption of a stock motor and aftermarket exhaust. If your bike has high compression pistons, aftermarket CAMs, or other performance motor work please specify below.

The CRs are pre-jetted to a base-line that's intended to be as close as possible, but fine tuning may be necessary for the individual bike. As such DCC will not accept returns due to 'jetting'.Sold as a complete set, includes plastic velocity stacks, CR29's shown in photo's.

Racing Carburetor Tuning

Despite what you've been told, that little 300lb gasoline powered love mochine of yours isn't giving you all she's got. If your still running stock Keihin carbs that is. Don't get us wrong, we build plenty of bikes with them and they get the job done, but if you're after twist rip riot performance and simplicity theres simply no other solution for carburetion on these old bikes.The two biggest advantages are pretty basic, but they make a huge difference when getting that pavement pounder tweaked and geaked for Friday night streel brawls.

First, they have integrated vacuum ports specifically for tuning, allowing you can dial them to perfection with a set of carb gauges. The second, and probably most important, is the fact that they're controlled by actual cables vs. Vacuum created by cable movement. One of the biggest problems with the stock Keihin carbs is slides sticking and with these bad-boys you can kiss that goodbye like that bump you got ointment for last month!Not to mention these babies have been the choice of Team Honda for years on all of their in-line 4-cylinder race bikes in Superbike, World Championship Endurance and Formula One classes. That has to count for something!Designed for use on sidedraft four-stroke motorcycle engines you'll uncover hidden power and performance in your two wheel terror simply by bolting them on.

The kit comes complete with everything you need to get the job done in an afternoon, even the velocity stacks.If performance is something you're not willing to sacrifice, these are the carbs for you! Dime City Cycles is the premier choice for DIY custom motorcycle parts, accessories and life style gear. Whether your interest is Cafe Racers, Bobbers, Choppers, Brats, Trackers, Scramblers or you just want something a little different for your current ride, you are sure to find the parts you need right here.We offer world-class customer service and we have an in depth knowledge of all the parts we sell, so if you have a question or can’t decide if a particular part may fit your motorcycle we are here to help.We also know that sometimes things happen, or parts don’t always fit like they should. If for any reason you are not 100% satisfied with your purchase, just give us a call or send us an email and we’ll do whatever we can to get you smiling again.© 2019 DIME CITY CYCLES.