OKO K-100 Series of Carburetors in a "Nutshell"
The OKO  "D" slide carburetor  has become of particular interest to off-road riders lately, as well as road riders, due to its ability to provide extremely smooth running at all throttle settings and instant throttle response, while extracting more usable power from  engines  than "round slide" carburetors.  The slide edge is set much closer to the needle and nozzle than in round slide carburetors.   Air flows faster and smoother through the bore due to the slide and jet block configuration, which helps create a smoothbore effect.  The high velocity of air flow means a stronger vacuum at the needle jet, providing more precise metering, better fuel atomization and therefore better throttle response and power.

The real beauty of the OKO "D" slide design is that it has enabled OKO to simplify the jetting of the K-100 series.  The older technology of round slide carburetors, required the use of many different slide "cutaways" and a variety of needle jet sizes and needles.   The "D" slide technology developed by OKO has eliminated the need for various slide cutaways, needles and needle jets.  For trials applications, one needle has worked correctly for the 19mm through 28mm carburetors which are used by all of the trials bikes we have tested from 125cc to 350cc.  There is only one size needle jet and one slide cutaway for each size.  The key to "perfect" carburetion with the K-100 series is in the size selection of the carburetor.  The correct size ensures a smooth transition of the main circuits within the carburetor.  So tuning, basically boils down to selecting the right size carburetor for your engine and finding the correct size pilot or slow jet and main jet.  When developing a kit for a previously untested machine, we first select the size according to engine cc's.  Then we adjust the needle position for that size carburetor, and then adjust the slow and main jets.  Once the slow and main jets are right, the final determination is in how the bike performs in the transition area between the pilot and the main circuits.  Richness in this area is cured by switching to a larger carburetor, while leanness is cured by switching to a smaller sized carburetor.
To a tuner, this is a blessing, as several tuning factors of round slides have been eliminated.  At the same time, smoother running and idling, better throttle response and more power are obtained.  This is why we are using the OKOs in our own bikes, promoting and selling them to our fellow riders.

It should be noted here, that the OKO is being copied by many other manufacturers in China.  On the outside they are virtually identical, and their packaging proclaims they are OKOs.  Internally however, the slow or pilot circuit is poorly designed and does not function correctly.  Often these copies come with unmarked jets.  The bottom line is that they are nearly impossible to tune correctly.  Care should be taken to find genuine OKOs, and we have provided a page here to help you discern the difference between the OKO and one of the many copies.

Thanks for taking the time to learn about the OKO K-100 series of carburetors.  We have been "won over" by these after tuning AMALS, Mikunis and others for many years.  We stand behind all the OKO products, and are here to help anyone interested in trying these on their motorcycles.  Take a look around our site for more information and to purchase one of our carburetor kits or accessories. 

Welcome to USA-OKO's information page for the OKO K-100 series carburetor.  We have been using, installing and tuning these carburetors since early in 2012 , and have been using many of these bikes in our Mid-Atlantic Vintage Trials series.  Thus, we have been able to evaluate them under real world circumstances, gaining knowledge and sometimes dispelling mis-information about them.  We have found the OKO K-100 series to be quality carburetors that are easy to tune, and that give superior performance over  many other carburetors.  We have several pages devoted to informing you about OKOs, their applications, tuning and maintenance.  Follow the links that interest you, and contact us if you have any questions about these carburetors.
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