OKO

Discussion in 'Trials' started by heffergm, Dec 4, 2017.

  1. heffergm

    heffergm Long timer

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    So I got the OKO on the GG tonight. I'm not sure what the hell they expected me to do with the throttle cable... it's way too long with the OKO top, since it doesn't have the long collar that the Keihin has, so I just used the top off the Keihin.

    Aside from that, it looks pretty well made... it's almost an exact knock off of the Keihin with a few small observable differences (although permit me a moment to relive how much of a pain in the ass it is to get the throttle cable attached to the slide).

    The only real 'feel' difference is with the slide spring. It feels like all the TRS's I've ridden, which is to say, heavy, or at least heavier than I'm used to.

    As for jetting, first off, I'm amazed at how sensitive this carb is to air screw adjustments. Very small changes make a huge difference. It's jetted 120/52/JJH. At 3/4 of a turn out on the air screw, it runs pretty well most everywhere. The one exception is putting it in fifth and grabbing a big handful, it'll bog a little. I'm tempted to go up to the 55. What say you?
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  2. Boom Boom

    Boom Boom Been here awhile

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    I have only used them on vintage bikes and just used the make your own cable set up. On the Bull it needed a larger main than what I was told it should need but once fed proper I was impressed with the improvement. Have one on a TY-350 now, happy with that also.
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  3. heffergm

    heffergm Long timer

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    Good call on the cable!
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  4. motobene

    motobene Motoing for 46 years

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    So true on the air screw sensitivity, just like Keihin! My Sherco 250 is boggish to a bit dirty within a half turn of the screw. I typically can set a carb and not change it but rarely. Not so this particular 2017 Sherco 250 with Keihin, as it has to have a smallish 48 low-speed jet to not run dirty. Contrast that with my 2016 which ran strongly and cleanly with the 55.

    As for your 52 and bogging, check the air screw turns out. If you are inside 2 turns out then yes, I'd run a 55. Caveat on riding styles that are shallow on throttle openings.

    You are running my recommended OKO jets. The 52 is the safe bet jet to cover many bikes and riding styles, but some bikes like the 55 better.
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  5. heffergm

    heffergm Long timer

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    So I ended up chasing my tail for a while until I thought to check the float height, which was a million miles off. In the interim I ended up going to a 55 pilot, a 122 main, and raising the needle (lowering the clip, i.e. richer), and I was still getting a bog going from small to large throttle openings semi-quickly under load. Once I fixed the float height that went away.

    The jetting still seems about right. I'm around 1.25 turns out with the 55 pilot, and the 122 seems fine on top.

    My two remaining issues right now are a bit of a flat spot when transitioning from small throttle openings to large. No bogging, just not much happening until it gets on the main. So the needle isn't right, but I'm not really sure which way to go. I'd say it's still lean, but that seems weird.

    The other problem is that it's really sensitive to down/uphills. The idle will really drop when headed down and rise when headed up. More than I'd expect.
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  6. motobene

    motobene Motoing for 46 years

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    Idle change like that can come from a float level that's a tad high. I find the Keihin/OKO like lower float levels to stay clear of jostle and downslope enrichment. I went from 19 to 22mm on the '17 Sherco 250 to get rid of the same.

    A little more tail chasing to consider is lower the float bowl depth (float height) a little, and run your needle higher by lowering the clip one or two more.

    And every bike and carburetor is an individual. Your air screw is still pretty far in, so a 58 low-speed jet may be what your particular bike craves.

    In sum, slightly more optimal may be going leaner on the float, and richer on the low speed jet and jet needle taper position.

    And there is one more trick: fitting Boyesen CarbonTech reeds. The little bit of difference between them and stick reeds will either be additive or subtractive to performance. No way to know without trying them and maybe fiddling a bit more. The fixed my '16 250 for sure. I have them in my '17 250 too, but that one was an odd ball that didn't like larger low-speed jets. I never did go back to stock reeds, but now the '17 runs SO sweet I won't.

    It's not unusual for me to take months to iterate into more optimal jetting. It's a process few care to do, but when others swing a leg over my bikes, they pick up on that level of detail.
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  7. Norman Foley

    Norman Foley Devotee of the Husqvarna

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    motobene, I may have asked you this before..... Did you put Carbon Tech reeds in your '17 125?
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  8. motobene

    motobene Motoing for 46 years

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    No. Just needed a 58 low speed jet. That little Sherco motor runs better than any 125 on earth, and is smooth everywhere. Why mess with a good thing when the stock reeds work fabulous?

    My 250s, on the other hand, I have found to be persnickity, some taking months of subtle iterating to finally get to working like a dream, as in both smooth and grunty powerful. And yes, I do fit CarbonTech reeds to the 250s.

    Most of the 300s I have ridden are smooth and way powerful set up stock, and they typically only benefit from the usual larger low-speed jet.

    So what would happen if I fit CarbonTech reeds to the 125? Dunno. I am insane busy with other things, so it's like 347 down the list, as in never gonna happen. My ADVrider time is limited to my coffee and 'morning constitution' period:knary
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  9. Norman Foley

    Norman Foley Devotee of the Husqvarna

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    Mike Komer concurs on the reeds. Thanks!
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