neo

Hi Gents, Yes the one on the left is a 30mm OKO. I bought it 2 years ago. It has an elliptical bore so it the same width (opening) at the bottom as the 28mm, but 30mm high....hope that make sens. I originally went for the 30mm because they are very cheap (unusually) and the Keihin was dripping all over the shot at that time. It kinda ran OK too, until the my 250 started getting the "hunting on idle" problem. Then I swapped back to the Keihin in an effort to cure the problem. Cope I do have a spare metal bowl...but it's only an OKO (taller) one. I used the Keihin metal bowl on my 26mm to make is a looser fit. The OKO one will fit but it will rub and wear the gearbox case. You'll laugh but I a have glued and 5c piece onto the that part of my case and neither carb or case seem to be wearing now as a result. The plastic bowl is still a good option....It as low as the Keihin bowl but only wears out the pain on the case. Tony, Jetting for the 26mm is the same as the 24mm....M:112, P:38, and JJH needle (middle clip). But this time I am running Boyseen reeds.....So you may want to try a P:35 if you don't have duel stage reeds. I got this Carb 26mm Carb from the Thumpster market...the setting it came with were M:100, P:35, and JJH needle (middle clip)....if I recall correctly. Dave, thanks for reminding me about this.... I have increased the float height to 21mm (@ 45 degrees). All these Keihin's and OKO's run rich on steep descents and the idling drops as a result. With the carb installed at such a steep forward angle and the pilot jet outlet right at the front of the carb I'm convinced that 19mm is too high for a Sherco installation. This is not fully tested but I've noticed no negative effects to setting it to 21mm yet. And I the idling has not dropped on me yet. I have a couple of more things I'd like to try....Ones a GJH needle and the others a quick action throttle......But even if nothing else changes I'm gonna be a happy man for a long long time Best of balance. Neo

Hi All, After fully testing the 26mm OKO on the rocks I can safely say I will not be going back to the Keihin PWK28 again. Because on my 250 it's better all round. Combined with Boyseen Reeds it's Smoother off the bottom, more controllable and has (what seems like) just as much power as the 28mm after one third throttle. Tuning seems much more stable and less effected by climate changes. If I were competing in lower grades I'd still go for the 24mm but for me the 26mm is all-round all-better!! I thought I'd include a photo of my current family, just for good measure..... NB...the new OKOs come with an angled throttle cable tube (the tube/cap on the Keihin on this photo). Which is great but this does not unscrew like the previous carbs and the Dellorto. This may lead to cable/wire length and cable adjustment issues. I'd guess you could partly correct this by using one of those universal replace throttle wire kits. But I'm not sure how you could introduce an inline cable adjuster. If your converting from a Keihin or an older OKO just use the cap off of there. Also, watch out for that deeper bowl. as mention in the "OKO 24 Rock Test" Best of balance. Neo

WOW!!!....someone should use the bottom end technology of that engine on a two stroke.....it looks like it would make a lower profile engine than the side-vale gassa.. Best of balance. Neo

Everything but the slide.....the OKO slide will not go inside a Keihin....it's just a fraction bigger and jams half way down....The Keihin slide has a much better chrome plate on it too. That power jet and tube has been on our 24mm/125 for a year or so....I've seen no I'll effects so I'd leave it as it is for now.....I still wonder why and how the 24mm carb spits/spills no fuel....is a very clean carb. Another thing I've noticed is the standard OKO metal bowl is a couple of mm deeper than the OKO clear plastic bowl or the Keihin metal bowl. So in theory it will rub harder against the gearbox case on the 290/250....So I'd recommend that people buy the plastic bowl.....It's good fun watching the floats go up and down while your riding too I've just got hold of an OKO 26mm....It comes with a 100 Main, 36 Pilot and JJH needle...so not that far out.....but it does not come with the power jet and tube....so I'm interested to see how clean it keeps compared to the 24mm. I feel the "The OKO 26 Rock Test" coming on this weekend too Best of balance Neo

Wow....you got a good result without even touching or knowing he setup....That's AMAZING!! Best of balance. Neo

Thats' interesting news Bob.....let us know how she goes on the trials test? Also, What jets and settings did you use? Best of balance. Neo

Hey Cope, If you buy an OKO24 I don't think you'll be disappointed. ......but next time don't forget to bribe me with some of those Carbon Fibre swing-arm guards of your But in addition to the other points Ive notice that the new Dellorto VHST they are fitting in Europe is also 26mm. The OKO dealer here is OZ is also selling kits based on the 28mm and 26mm OKOs Best of balance. Neo

Wow!!...this is great information Marlintec.....your website is fantastic ...but I keep forgetting to check back there. Can you please tell me how a sleeve is fitted to a Keihin PWK 28? What is the sleeve is made of and how is it kept in place? ...Are there any disadvantages to doing it this way? And Could I use the same principle to make it a 25mm Carb? Best of balance. Neo

Ok the faulty components I changed were the main bearing seals (both of them) and the piston rings (which contributed to the problem). The symptoms were engine Hunting (running lean) at idle then running rich on the slightest clockwise adjustment of the air-mix screw. The problem was intermittent and in the early stages would only show with the combination of a low fuel tank level (below half) and a long ride on a hot day. Gearbox oil was lost (burnt away) at a very slow rate (100ml per 6 months). The seal on the generator side wears faster than the oil side but there was no sign of this until the seal is removed. What I

Hi Cope, Yes identical to the one pictured.....Do you know what that balance tube is doing?....I've only seen it on the OKO 24mm. The 24m OKO is often used on Thumpsters (Honda 4 banger copies) and I picked my one up from that market place about 12 months ago. OKO's are also popular on scooters too and stuff is available for a lot less money than you normally pay for Keihin stuff. I've purchased clear bowl too for my one. It 's odd but the rubber bowl seal swells in the first few weeks of use but is fine again months later.....Also, even though the vent in on the muffler side this carb rarely drips and keeps itself as clean as a whistle. ...so there's no need for all that tube work I have on my Keihin PWK 28. Borus, I appreciate your feedback but I am specifically referring to the Sherco 250 (and poss 290). XiSPA's will have their differences to the Sherco's. I know the header pipe and exhaust box are different not to mention the possibilities of port timing, compression etc, etc. Honestly I'm not knocking the 28mm in any way, it's a great carb, but I think it's application is borderline on a 250 Sherco. Go for it bobtlr. ...let us know how you get on? Best of balance. Neo

Now I know what you mean tony...I had to file the outer edge of the screw heads a bit to make the reed block go back in. But on the plus side, there no way these screws could ever undo themselves and come out Best of balance. Neo

OK.....final conclusion is it much much better....but not perfect. On a hot day after some prolonged riding she's just beginning to hunt on idle. It's very lightly but not enough to effect my riding at all......So it's not a perfect result but it is a vast improvement. I'm continuing to hunt for the Hunting (see my new post) but I think this thread has now fully lived it's purpose. I want to thank clav, cope, HAM, Jon, PeterB, Ralphy, Stork, tony and trialsnutterman for your dedication and efforts in resolving this problem. Best of balance to all that read and contributed to this thread. Neo

Ok as discussed many times in past posts (and at Cope's requests) today I fitted an OKO 24mm to my 06 Sherco 250. Firstly, after removing the OKO24 from my 125 I made a note of the current settings....M:112, P:138, and JJH needle (middle clip) then slapped it on there using the slide (and JJH) from the Keihin, which went straight in. Started her up, warmed her up, adjusted air mix (leaner) 1 3/4 turns out, raised the idle and took up some slack on the throttle cable......Hmmm. she seem to be running nice....so let's take her up on the rocks I rode over some very familiar sections and I have to say the results were excellent!!! .. For starters there was FAR MORE CONTROL over the power delivery yet the power was still there when it was needed. Secondly the power was consistent and reliable and I found myself pulling up and landing the front wheel with a great more accuracy then I have ever had before. If I was competing "C" Grade this is the carb I'd want on my bike. And to be honest after 2 hours of riding I was finding it hard to give this carb back to the 125. Ok the down sides.... 1. Although the engine will still rev clean to the highs it does take a split second longer to get up there. I did a few small splatters but I didn't find it limited the bikes abilities in any way. If fact I found myself with greater control of the bike when it landed on top of the rock. 2. When I rode some flat track stuff I put her into 5th (at a lowish speed) and whacked the throttle wide open. The engine struggles for a bit longer (than with the PWK28), but it still manages to pull it's self into the power band. But here's the "big one" (for me than is) .....at no time did the engine hunt at all .....so I personally confirm Cope's suspicions that a 28mm Keihin is too big to tune to perfection on a late model Sherco 250. Such was the improvement that my money is now going on a 26mm OKO soon. But again, if I were competing I would be buying the 24mm. Make of this lot what you will!!. Best of balance. Neo

Thanks Tony, Sorry for the late reply. Best of balance to you Neo

Same as the 02 if I remember right. Best of balance. Neo

The 02 to 05 are no where near as hard to do as the 06 onwards shocks. Best of luck. Neo

Just worked out that this Mitani unit is not meeting one of the primary goals..."Cheaper than Sherco" the purchase price alone (without postage) is more than I paid Sherco Best of balance. Neo

So it should read All SHERCO's and 95-03 GASGAS Your guess Cope is as good as mine. I think it's a better device though. Because on the Sherco thermostat the fixed spade connectors rub up against the tank. Best of balance. Neo

Well Spotted shercoman Akira Makoto is in effect puts a very fragile credibility. High quality parts at a very cheap. RTL250R Reliable switches employ RTL250R genuine products! ! However Samosuitchiatatchimento is produced in high quality aluminum and is also highly corrosive damage anodized black! ! SHERCO 95-03GASGAS 9,800 Adaptation models: SHERCO 2 strike all models 95-03GASGAS

TOTALLY disagree.....it's because it a Trials bike, ridden with more precision than any other motorbike, that it need to be perfect (engineering wise) Don't know (don't care) how many man hours but when I think about riding (and how much I have learnt) it's been worth every second. Best of balance. Neo

Oh my God!!!...that bad eh. But just to confirm....these are the same "express" name business that has Cabestany decals up there at the present time? Best of balance. Neo

I've bought two sets of these some time back and have these in storage......What bad things have you heard?? Best of balance. Neo

Patience my friend patience ....Rome was not built in a day an neither was an OKO Thanks for the info Clav...makes lots on sense now. ...I will try and perform the transplant once I have the reed screws. Rode again today...fine tuned the mix a few times but apart from that all seems good. I have noticed change in the engine as it sounds crisper and the power is dependable and the exhaust is smoke free at all times. But it seems that the engine is running 5 degrees hotter that before. Used to be around 58C now it's around 62C...is this normal? Best of balance. Neo

Just to clarify....it is the tiny cross-point screws that hold down the actual reeds (not the reed block) that I need to fine the size of? The 06 parts book does not have a number for these....so assume they're included with the block. Many thanks. Neo

Hi. Does any know the size and thread of those 4 small cross point screws that hold the reeds to reed block?. I messed mine up trying to unscrew them today and need to buy some more on Monday. Also, once you fit Boysean reeds what changes to the pilot jet are needed? Best of balance. Neo