Kits for Yamaha TYs, TW200, WR200, ITs, SR500
The Yamaha TY 175 and TY 250 are two bikes that take the OKO K-100 series of D slide carburetors without much fuss. The existing rubber manifold boot is used and is a perfect fit. The cable on the TY 250 does not need to be changed or modified. The rubber boot from the air box has a slightly smaller inside diameter than the intake of the OKO, but once the boot is heated, either in hot water, or carefully over a flame, it softens and can be stretched slightly for a good fit. Because the TY 175 uses a smaller stock carburetor there is not quite enough free cable length for the K-101. We have used a cable from the TY 250, and we offer the Venhill Universal throttle cable as an accessory here. Also, the stock outer cable can be used but with a slightly longer inner cable (or shorten the outer cable a little).
After experimenting with different sized carburetors on the TY 175, the 21mm proved to provide the very best low end power and best overall performance for stock 175s that use the stock exhaust and air box. However, if you are using a large resonant air box, or a UNI filter in place of the stock air box, and the WES or other free-flowing exhaust, we've found the 26mm to give better performance from the bottom end to top end. Select the size you want when ordering. Also, the stock throttle cable does not have quite enough free length, so we offer the Venhill universal cable here at a reduced price with the TY175 kit.
Order your TW 200 kit from the drop-down list to the right and let us know what madifications your engine has, especially if the engine has extra cc's.
Below is my personal 1975 TY 175, fitted with a UNI "sock" filter, Boyeson Power Reeds and a WES exhaust system. This bike jetted considerably richer than the stock 175 above, and ultimately we stuck with the 26mm for it.
Optional clear float bowl
OKO K-101 Clear Foat Bowl
OKO offers this clear float bowl for the K-101 series so you can easily check the float level, or see if any dirt or water has accumulated in the bowl. It attaches with four screws (incuded). It does not have the bottom nut for access to the main jet. This may be purchased by itself or with a K-101 Carburetor kit. Click on the "options" below.
This angled top for the K-101 is sometimes the answer to limited space above the carburetor on the TY 250. It uses slightly more free cable than the straight top.
This universal throttle cable kit from Venhill comes with everything needed to create your own custom throttle cable. Outer housing and wire are over 4' long with an array of fittings. Slide end is already attached.
Now included: Solderless throttle end with cable.
The Yamaha TY 250 with the stock exhaust and airbox uses the 26mm OKO. If the exhaust, reeds and intake are modified for better flow, then the 28mm can be used if you are looking for a bit more top end. For riders more concerned with low and mid-range power, the 26mm is the way to go. Please select which size you want when ordering. The kit comes jetted for your 250 with the correct needle and a shim for the needle for fine adjustment. We provide extra jets to help you dial in the carburetor according to your engine's modifications. The benefit of ordering the TY kit over the basic carburetor is that the extra jets provided you can exchange until you have it jetted just right. Below are a few of the TY 250s we have fitted with OKOs here. One of these was all stock and the others had been modified to breathe better with UNI filters and modified exhausts. The modified ones jetted slightly richer or used the 28mm. Note that these kits come with the straight, adjuster top which we prefer over the curved top unless absolutely needed.
Order your TY 250 kit by selecting the shipping destination on the drop-down list to the right, as well as the size carburetor you want. Don't forget to tell us any modifications to your engine (cc's, reeds), your airbox and/or exhaust.
Order your TY 175 kit, either the 21mm or the 26mm, depending on modifications to the intake and exhaust and be sure to let us know about intake, reeds and exhaust modifications. If you would like the UNI sock filter and /or the Venhill throttle cable, both are available here at a reduced price.
We have not had the opportunity to work on a TW 200 here, but have worked with owners of this Yamaha, replacing the stock carburetor, which no one seems to be happy with. After experimenting with a 24mm and a 21 mm, our clients chose the 21mm which gave excellent power and response throughout the throttle range. Owners we have dealt with have replaced the twin pull cable with a single pull cable. The carburetor fits directly into the stock manifold, but the airbox hose will need to be modified to fit. Once we have had one here at the shop to work on, we will provide the needed airbox adapter hosing with the kit. For now we offer the 21mm with the curved top, and jetted for the 200. We provide extra jets for fine tuning to your engine, exhaust, etc... and work with you to see you get it dialed in right. We believe this is the carburetor many TW 200 owners have been looking for to solve the woes of the stock carb.
We have added to this page, some of the options you may want to add to your order. The clear bowl lets you see the status of your fuel is (low, water in the bowl, etc...). Sometimes the curved top gives a better angle for your throttle cable (stock with the TW200 kit).
The Venhill Universal throttle cable is a good quality, made in England, product and comes with ends and adapters.
We have finally had the opportunity to fit an OKO on a nice TY 350, and once we replaced the wrong reeds with new, correct Boyesen's, we are happy to report that we now have a 28mm kit for the TY 350 that provides smooth, strong power. Wheelies in fourth gear from a crawl are done with little effort. It's hill-pulling power is phenomenal. We tried heating and stretching the airbox hose to fit the intake as we do with the older TY 250s and 175s, but the 350's air box hose was a little stiffer and we ended up cutting off about one half inch of the stock hose and sleeving it. We offer the sleeve with the kit, but with more patience than we had, you might be able to use the existing hose. The length is just right. In order to keep the stock throttle cable we had to make a modification to the carburetor end. The stock cable has an adjuster that the curved top threads into. We used an OKO curved top, then threaded a carburetor top adjuster into the TY's adjuster and drilled out the end to slide over the OKO's curved top. We leave that up to you, whether you want to modify the existing cable or replace it. We offer a discount price on a Venhill cable with this kit if desired.
Order your TY 350 kit from the drop-down list to the right and let us know what modifications your engine has, especially if the engine has extra cc's or an aftermarket exhaust. Select the right shipping destination. If you also want a throttle cable with the 350 kit select that as well.
We have worked with our customers off-site to develop a kit for the Yamaha WR200. The kit includes a 30mm carburetor (OKO D slide of course) with a curved top and jetted for the WR200.
It comes with extra jets for fine tuning which can be exchanged if needed. Our customers tell us the OKO eliminates the mid-range "blubber" and increases power and throttle response. Your manifold and airboot do not need to be modified, but your cable may, so you can add a cable if needed, (above) when ordering this kit.
Curved top as shown here is no longer available.
It now has no adjuster.
We have finally gotten our hands on some Yamaha ITs, the 175, 200 and 250. Our best results came from using a 36mm K-104 OKO carburetor for the 200 and 250, while the 175 uses the 32mm. Fitment into the IT's manifold is good, as is fitment into the air boot. We used a curved top on the 175 and the 250, but there is room for the straight top. We can supply a curved top if needed, but because they screw into the top, the need to be unscrewed a few turns so when screwing the top on the curved portion can stay in place. The stock throttle cables for these bikes will most likely not work with these kits without modification so you may want to purchase one of our Venhill Universal cables. We use this cable ourselves when installing the OKOs. These kits will give a noticeable increase in power, especially in the low and mid-ranges. We used new cables with our installation. They can be purchased below if needed.
I purchased this 1981 SR 500 in early 2022. It was transformed into a Cafe Racer, fitted with a 10:1 piston, given a mild cam, and had the head massaged a bit. We fitted a 36mm K-104 OKO carburetor into the stock manifold. Since we had already eliminated the stock air box we fitted a UNI sock filter on the intake. So our kit includes the 36mm carburetor jetted for the SR500 and extra jets for fine tuning. Without our engine mods we believe it will jet just a little leaner.