bigears Posted February 18, 2009 Report Share Posted February 18, 2009 hi has anyone fitted an oko carb to an 07 sherco 250 and wots the benefit please is there any difference between oko and kiehn as they look exactly the same Quote Link to comment Share on other sites More sharing options...
copemech Posted February 19, 2009 Report Share Posted February 19, 2009 No! Standard carb works fine if properly tuned. If you need more power than a 2.5 can provide, well, most that are at that level just get the Kiehin! As there can be soo many small internal differences that it is not worth the bother! Quote Link to comment Share on other sites More sharing options...
neo Posted February 20, 2009 Report Share Posted February 20, 2009 The quality of the OKO is lower than the Kiehin....but not by much. All parts (except for the slide) are interchangeable. Jetted right (same as Kiehin) you can get good results for a 3rd of the cost of a Kiehin. It makes little difference if you get the 28mm or the 30mm OKO (30mm are sometimes cheaper). Because the 30mm Venturi is elliptical and the same as the 28mm for the first 70% of the throttle opening. Watch out for the rubber Float bowl seal. Given the chance it will expand after it's been exposed to petrol. And this makes it hard to get the bowl back on. But oddly enough it stops doing this after you've been using the OKO for 6 months or so. Having said all this Cope is right. With the OKO the power cuts in quicker then the Dellorto but that may not suit your riding style. As it can break traction easier. So, if your looking for smooth low-down power delivery I'd stick with the Dellorto. Also the OKO/Kiehin use more fuel than the Dellorto. Best of balance. Neo Quote Link to comment Share on other sites More sharing options...
trialsnutterman Posted February 20, 2009 Report Share Posted February 20, 2009 If you bung up the overflow on the Keihin it will use the same amount or less fuel than the dellorto, depending on jetting. The dellorto doesn't have a overflow that's why they don't spill fuel. I've run my Keihin with the overflow bunged for the last 4 or 5 years, it runs fine the only time it does cause problems is when you drop/fall off the bike and sometimes when queueing on a extremely steep hill it can flood the bike slightly making it hard to start. It does make me slightly more environmentally friendly though. Quote Link to comment Share on other sites More sharing options...
neo Posted February 21, 2009 Report Share Posted February 21, 2009 If you bung up the overflow on the Keihin it will use the same amount or less fuel than the dellorto, depending on jetting. This is interesting information trialsnutterman although I don't know why you would bung these up when there main purpose is to equalise air pressure in the carb. In other words they're allow the float bowl chamber to breath in rather than out. Maybe it's best put tubes on these vents then loop the tubes over the top of the carb so it cannot overflow easily. But can breath (suck) back any split fuel. Might try this myself Best of balance. Neo Quote Link to comment Share on other sites More sharing options...
trialsnutterman Posted February 21, 2009 Report Share Posted February 21, 2009 Hi Neo Your talking about the breather pipe, yes your right these definatly don't want to be bunged up, in fact I even drill the left breather out as the right one tends to melt the plastic pipe sealing it closed as it is very close to the exhaust. The over flow is at the base of the bowl and may possibly help with the pressure equalisation if the breather where to get blocked but its main job is to prevent the bike flooding if the float valve gets stuck open for some reason. If you try bunging it up with a short bit of pipe with the end melted closed or folded over on its self and held with a cable tie, its is dead easy to remove replace for testing. Let us know how it goes. Quote Link to comment Share on other sites More sharing options...
neo Posted February 21, 2009 Report Share Posted February 21, 2009 (edited) Hi trialsnutterman, Oh I get it now...thanks for clearing this up. I put the right hand side pipe inside a spring. It stops the pipe kinking and dissipates the heat so the pipe doesn't melt it. http://www.trials.com.au/phpBB3/viewtopic....ilit=PWK#p11369 BTW, the 24mm OKO I have on our 125 Sherco has a pipe from the top corner of the float bowl up to the outlet (reed side) of the carb. And this carb dose not drip at all from the bowl overflow. Best of balance. Neo Edited February 21, 2009 by Neo Quote Link to comment Share on other sites More sharing options...
neo Posted March 8, 2009 Report Share Posted March 8, 2009 The over flow is at the base of the bowl and may possibly help with the pressure equalisation if the breather where to get blocked but its main job is to prevent the bike flooding if the float valve gets stuck open for some reason.If you try bunging it up with a short bit of pipe with the end melted closed or folded over on its self and held with a cable tie, its is dead easy to remove replace for testing. Let us know how it goes. Yep...I've been testing it for a few days now and it's working well. I haven't blocked up the overflow as such. Just in case it does help with the pressure equalisation I've just taken a small length of clear tube and pointed it straight up. The tube just fills with fuel to the same height of the pipe inside the bowl and stays that way. So I'll monitor what happens after I "drop/fall off" the bike (a few more times!) to see if there are any ill effects this way. Interesting, I was reading that Japanese Carbs must have bowl overflows to cover the event of faulty float vale flooding (as you said trialsnutterman).....And it looks like they serve no other purpose. The other thing I did was to take both breather tubes and loop them over the carb then down to the back of the bash plate. And to minimise the chance of fuel moving too slowly through these tubes I have run smaller (short length) tubes into (pushed inside for 3 cm) larger (long length) tubes.....And she's running like a dream this week :-) I have run small full length tubes down behind the bash plate in the past but this had problems. The new setup keeps the Carb breathing (clean air), the bike clean (free from fuel spillage) and must save petrol too...So I'm really happy so far. Thanks for the pointer trialsnutterman Best of balance. Neo Quote Link to comment Share on other sites More sharing options...
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