For Those about to Rock... buying OKO Flatslides..

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AntNZ

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Ok, so what jetting have you ended up with now ?
Have ended up with 36 pilot 98 main and needle 1 up from middle, bike ran awesome right through rev range until a mate of mine valve bounced the s#*t out of it so need to do valves again and not let novice riders go near it, haha
 

my67xr

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Right,
there's not many 160's around that will run sweet with a #36 pilot and a 98 main.
If your engine made the pipe glow red then it was too lean, mixture screw turned out too far ?

I've only heard of 1 other 160 with an Oko 26mm that was able to run stock #36/#100 jetting and from memory it was rotn50's ?
But he is also up in the tropical north Queensland so leaner jetting is needed.
 

AntNZ

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Right,
there's not many 160's around that will run sweet with a #36 pilot and a 98 main.
If your engine made the pipe glow red then it was too lean, mixture screw turned out too far ?

I've only heard of 1 other 160 with an Oko 26mm that was able to run stock #36/#100 jetting and from memory it was rotn50's ?
But he is also up in the tropical north Queensland so leaner jetting is needed.
with 36 pilot and 98 main pipe is cool and engine doesnt run hot but had heaps of power all through rev range. I do have 35,37,39 pilots and 102,104,105 and 106 main to try if you think it is worth a go. never tried 39 pilot or 105 ,106 mains as i thought it was too rich with 102 and/or 104. The weather here is never tropical, average temp at moment between 12-18 deg, never more than 30 and no humidity, what should i do?
 

AntNZ

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Finally!!!! got my bike running perfect, revs clean all the way through the rev range with no hesitation at any throttle position.
I ended up with 39 pilot and 105 main, needle in middle position and air screw 1-3/4 turns out.
I cant believe i ever had it running with 35 pilot and 98 main, hope i didnt do any damage to engine while running so lean.
Big THANKS to everyone here that helped me sort this carb, would have been lost without your advice!
Thanks again.
 

Luke918273

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Hey guys I got a 28mm oko running on my yx160 and ran into some troubles as the fuel/air screw is one click from being closed (clockwise), it runs pretty good besides when I open the throttle up too quickly and it bogs out, I’ve tried doing the best to tune it but can’t seem to get it right, do I need to go up or down in jet sizes? And yes it seems to be running rich by the smell and the look of the spark plug. Thanks in advance
 

Kingkerm1976

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Ok it seems a lot of people on here are considering buying OKO flatslide carbies in the hunt for a bit more performance.
Then it seems like everyone who considers it, finds out that the Flatslide is hard to tune, and doesnt buy one.
They arent hard to tune at all. No harder than a mikuni or molkt or anything like that. They offer great performance when they are tuned, BUT THEY ARENT FOR EVERYONE.
They are better suited to a more experienced rider, as they are a bit touchy with delivering the power, especially when used with a 1/4 turn throttle.
Basically a flatslide equipped mini, is like riding riding a two-stroke 125, without the outright power... bottom end grunt isnt great, but it builds into a good mid-range, then a screaming top end.
They will transform a stock motor into a bit of a top-end tearer, but they are best used on an engine that has had a bit of work done to it, such as an IRK, Big-Bore pipe, cam, or head work that makes the most of the breathing capabilities of the flatslide.
I run a 28mm flatslide on my custom 140 lifan, and a 26mm flatslide on my Atomik Blitz 250. Both bikes experience substantial gains when the flatslides were added, and both went from having reasonable power overall with the standard mikunis they came with (24mm and 26mm pumper respectively), to having power that built strongly in the mid range, into a screaming top end. Seems to be a bit of a trend/quirk with the Flatslide.

Most of the threads on here state the OKO flatslide as being hard to tune. They are no harder to tune than the mikunis, but generally are delivered with jetting that is way off the mark, particularly the main jets. My 28mm came stock with a #195 mainjet... which is about twice the size needed.
It seems OKO grab whatever main they can see, and chuck it in...
The OKO Flatslides are great carbs to WORK on.. The main jet can be changed without removing the carby from the bike, through the drain plug, the air-screw can be adjusted from the left side of the carby without removal from the bike, and the needle jet can be accessed by loosening the rubber manifold clamp that comes with the carb, and tilting the carb on its side. Try tuning any jets on the mikuni without removing it from the bike... depending on the bike you have, you MIGHT be able to do the needle... So as far as working on the carby itself, the OKO Flatslide just reeks of pure WIN...:cool:
Like the mikunis, the OKO's have a pretty standard starting point when it comes to getting the jetting right... the pilot, air screw and needle are pretty much on the mark.
The mains are the problem. I've found that they are jetted very rich standard, but the thing that seems to make them so hard to tune, is that they give the opposite symptoms from the problem. IE: they seem like they are running lean, when they are actually running very rich...so you throw a bigger main jet in, and get further and further away from getting it right. Took me a LOOOOONG time, and lots of dollars in main jets to figure that one out... sadly plug chops dont always help with the tuning, as they just dont run/burn until the jetting is right.

So if you get one, leave the pilot and needle as they are...
When you buy your carby, request that it be fitted with a #95 main jet. Like the mikunis favour the #92 mainjet (which coincidentally is quite a bit different to the OKO #95 main jet, and not just 3 numbers out..), the OKO's are best started off with a #95. This will allow it to at least run well enough to do an accurate plug chop, and alter jets from there.
My 140 running the 28mm, was dyno-tuned, and gave out AFR's (air-fuel ratios) of around 12... which is pretty close to "perfect" tuning and safe either side of too much or not enough fuel... and that's with a #95 main..
Making sense yet? USE A #95 MAIN TO GET YOU STARTED.
Coincidentally, if you need to buy main jets, go to a dyno shop, they'll have heaps on hand, or alternatively, if you want to buy new ones, go to a Honda shop, and tell them the jets are the same as the Keihin jets used in the Honda CR-F 250...

Oh and finally, select the right carby size, for the motor you have. Dont throw a 28mm flatslide on a 110 motor.
use this as guide...
110-125 motor, no mods : use a 22mm or 24mm flatslide.
125-140 motor, no mods: use a 24mm
140cc with mild mods/150 or 160 no mods: use a 24mm or 26mm flatslide.
140cc with wild mods/ 150 or 160 with mild mods: use a 26mm or 28mm.
140-160 rocket ship motors: use a 28mm
150-250 Loncin/Zongshen upright motors- no mods: use a 26mm
150-250 Loncin/Zongshen upright motors with mild to wild mods: use a 28mm

So in closing, the OKO flatslides arent hard to tune. They're bloody easy to tune, you just need the right starting point. They are, admittedly, a little harder to get PERFECT compared to the mikunis, but i've found the OKO Flatslide when jetted close to perfect, offers more performance than the same size Mikuni jetted perfectly. obviously people will disagree, just sharing my experiences having run both types of carbies on my bikes, especially the modded 140 and 250...
keep in mind they will make the power a little more "light-switchy", but if you have the skills to ride one, ie, if you're a good 125 two stroke pilot, then the OKO is the fuel bucket for you!!!

If anyone has questions in regards to tuning them, fitting them, or want to add more info, please go nuts on here...
The OKO is a great carby bang-for-buck, and much more user friendly maintenance wise than the mikuni.
Dear Team

I am looking at a oko 26mm pwk for my yx140cc pitbike.
It has a high compression piston
88mm flywheel
Do you know what sort of jetting to start off with?
 

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