anyone jetted a oko 21mm with a bbk? Have some questions.

Does your Spree/Elite already run great, and you're trying to make it quicker/faster? Need a monster motor swap? Discuss your ideas here.

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airbats801
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anyone jetted a oko 21mm with a bbk? Have some questions.

Post by airbats801 »

I've been working on getting a carb to work with my 1985 guro up with a bbk, koso big intake/reed cage, and stock pipe. I originally started with a 19mm polini cp that I never liked, but had it. I couldnt tun it lean enough to get rid of a 1/4 to half throttle overly rich condition. Same thing when I had ran it on my ruckus, so I decided to toss a 21mm genuine oko non power jet carb I had been sitting on for years.

I'm surpised how big I have had to go with the jetting so far, and I feel like I finally got it somewhat under control. My cht have been out of control. I'm running a 45 slow jet, and right now a 120 main. I think it''s still a tad lean as my cht were creaping up with the middle needle setting, so I dropped it all the way down, and now cht seem to be keeping somewhat nice around 320 wot in high 80 degree heat. Before I moved the needle I was easily hitting 350+ on flats wot, and even partial throttle I am battle heat up issues.

I'll probably buy a fw more jets larger for the main, but I'm beginning to wonder if maybe I need a different needle profile. The scooter is also a bit sluggish for a bbk I feel. * my stock get ruckus can outclimb it, but this is a tad on the straights.

Anyone played with these carbs a bit, and have any suggestions?

As far as I know there are no air leaks I can find,
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harleyracer59
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Re: anyone jetted a oko 21mm with a bbk? Have some questions.

Post by harleyracer59 »

you need restriction on carb inlet so carb will draw fuel through the jets. I have a 21 oko on my 84ab07 bbk. go get a spray can lid, cut it down middle. mor like 60/40. take the 40% sized piece and set on carb inlet at the top. then put a hose clamp to secure it or slide you pod filter over it and carb inlet and secure all that with a hose clamp. re tune your jetting im 60ft above sea level and I believe im running a 32 pilot and a 105-115 main clip is second from top. I have the power jet model so you might need a bigger main jet. the piece of cap that's mot on yor carb inlet makes carb think its smaller and help give the carb the bit of restriction needed. fixes that huge dead spot off idle and it doesn't hurt the top end rpm barely any. as the slide opens to wot. the cap "passages" open as well, give it a try youll be impressed and surprised a cheap piece of cap fixes all those big carb problems. trim from the 40 % or 60% pieces down a little at a time to get the perfect size cover/ diverter.
airbats801
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Re: anyone jetted a oko 21mm with a bbk? Have some questions.

Post by airbats801 »

I'll have to give it a try, I actually just changed to a smaller diameter filter due to losing my somewhere on a ride last night, necked it down to fit my ruckus uni, about a half inch smaller in diameter. It really doesnt have a low end bog at all, it actually takes right off. it seems a bit lacking, but maybe its my variator weights. I need to lighten them up a bit I think. I did raise the needle up like you said before I read this as it was running too much fuel, and It seems to be running a lot better with the 120 main and the second from the top. I feel like there is more to be had, but I'm not sure if im expecting too much from a big heavy gyro up with a 66cc kit or whatever the malossi setup is. I really need to figure out a pipe for it I think.
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harleyracer59
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Re: anyone jetted a oko 21mm with a bbk? Have some questions.

Post by harleyracer59 »

im so jealous. you got a gyro up motor . I like the looks of the 84-86 nn and tg better but you hands down have the better drivetrain. vertical cylinder, power to both rear wheels, a variator, 4 bolt intake, bigger ports, and bigger stroke, plus actual aftermarket parts. compaired to the us engine, backwards horizontal cylinder (no exhaust options), peg leg power wheel, weak 2 speed trans, small ports, odd ball 3 bolt intake, NO aftermarket performance parts smaller stroke.
from what ive read and seen gyro up is very similar to the af01 lead engine.. tuning your transmission will help you out a lot. got any pics of your little monster?
airbats801
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Re: anyone jetted a oko 21mm with a bbk? Have some questions.

Post by airbats801 »

Yeah, they are quite a bit nicer of a engine, but waaay bigger. I compared my spare basket case engine to the roadfox, and its like twice as big, no way you would be able to swap them without extensive work.

I'll post some pics up this afternoon if I have time.
https://www.youtube.com/watch?v=at5f9dcjBiI at 3:00 there is a brief view of me, and around 5:45.

As for the tuning. I'm going to try dropping my slow jet down a bit and see if I get some mid back. I think maybe im running too large of a low jet. We will see though. I think I will also shoot for some 5.5 rollers or sliders.
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