OKO-No-Go

[Blaner]

well as much as i hate to pollute the forum with more jetting threads, i do have a problem!

usy tuning my OKO30mm but its not happy, idles well with air screw 1 turn out as ive got a 48 pilot in. 155 in for the main needle middle clip.

now initial pull off is great but as soon as the power hits around mid range, its completely dead, nothing, just a sigh as if its run out of juice. nothing happens if i pin it open and wait either.

if i tap off and give it a sec, or pull in the clutch it seems to recover and you can accelerate again untill the same thing happens. if you get back on the gas to quick it doesnt pull as long as when you give it a longer break.

Seems to be short of fuel in the bowl but have adjusted float and it is actually leaking out overflow a little so the float should be allowing max fuel into the bowl.

Carb in kissably clean and have pump it with compressed air, used thin wire to probe holes etc numerous times!

must also mention that i have tried a 152, 150, 148 and even a 138 main as well as a 42 pilot with no effect at all!!!

have not changed the needle however

what am i missing???

 

[Awk08]

have you played with the needle clip position ???

and is this motor absolutely airtight ????

i'd also be curious to see what a brand new plug would tell us right after one of these episodes

 

[Blaner]

have not fiddled with needle clip, its still in the middle. Motor is airtight with a perfect leaktest record. Comp is 155PSI.

i have a new plug il put in and give it a run.

Bike runs PERFECT when i swap back to my stock 26 mikuni with 330main

 

[Awk08]

try lowering that fuel level by adjusting the floats, could be picking up too much fuel from level too high, and raise that needle clip to lean the middle, just for a test run

 

[slickerthanyou]

Is the slide adjusted using the top cap screw to apprx 1/8". If not do that first, then put the floats at the correct level, not over or under- then do the air screw adjustment for highest and smoothest. I know with porting my oko liked 162- If problem still persists I'd check the gas tank line maybe a dirty screen on the petcock assembly or maybe your tank vent is clogged?

 

[Blaner]

Is the slide adjusted using the top cap screw to apprx 1/8". If not do that first, then put the floats at the correct level, not over or under- then do the air screw adjustment for highest and smoothest. I know with porting my oko liked 162- If problem still persists I'd check the gas tank line maybe a dirty screen on the petcock assembly or maybe your tank vent is clogged?

you talking about the cable adjustment on the top cap? il have a look at that. busy with float again right now! 162 is huge!

if it was the needle, it would still give some response at WOT, but i get nothing as if there is no fuel

fuel line in clear, ive checked that and yes i have a full tank of gas!

 

[Larry's Shee]

Don't remember if I saw it her or BHQ, but it was something about opening up the fuel inlet area and maybe different needle/seat. Does it seem like it's running out of fuel?

 

[Blaner]

yip, seems to have no fuel

 

[Luni]

Getting a pilot circuit correct on a PWK can be tricky if you dont know where to start. And if your pilot circuit is wrong, your jet needle and main will be wrong too.

On a PWK, to get it to idle, I turn the pilot screw all the way closed, and I use the slide adjustment to actually get the bike to idle (at temperature of course). Once its idling using the slide adjustment, Ill use the pilot circuit to determine how rich/lean I am.

Also, float level on a PWK 28/30 is 19mm. So its a little lower than the stock carbage, but its higher than a PJ carb (which is 16mm where stock is like 21mm).

If youre at sea level, Id estimate ballpark jetting for that carb for you would be somewhere kind of where youve had it, but a meaner main. Ive seen some crazy jetting configurations before. Ive seen a 150cc engine running a PWK 36 with super aggressive main jetting but less on the pilot so it will idle. For you, Id recommend trying less pilot, more main jet. Id put your pilot around a 42 with the slide adjusted so it idles without pilot circuit help, then set pilot based on where the highest idle occurs with the pilot screw. If your highest idle occurs 1.5-2 turns out, youre where you should be. If its more, youre lean, and if the pilot circuit wont even adjust it, youre too rich. As for your main, Id put it somewhere around a 160-170 range. It sounds like a lot of main, and it is, but 330 on a mikuni is a lot of main too. I could be wrong tho. I know its kind of expensive to buy a bunch of jets just on someones thoughts, but its always a good idea to have em on hand anyway.

Ill give you an example of odd jetting, but it works. My buddy has a suzuki RM250. That engine is making more HP than ANYONE on this forum with a blaster engine. I can almost guarantee it. Its stock in the 50s. With his head work and recent rebuild, with the pipe he has, hes prolly around 60. He is running a PJ34 carb. Some of the guys on here are running PJ34 carbs. Weve got him dialed in at a 55 pilot, and a 165 main. Thats in the ballpark for what some of the blaster guys are running. Kinda odd, but what works works.

 

[Larry's Shee]

30mm OKO Carbs - Banshee HQ Forums 30mm OKO Carbs - Banshee HQ Forums +drill +needle +dry&fromsearch=1&#entry1119553

lets see if I did this right

 

[Larry's Shee]

I didn't read it tho, that's on you

 

[Blaner]

ok i hauled out the goold old Colour-Tune 500. got it idling nicely at 2.5 turns out with the 48 and its blue as i rev up slowly which is good but as soon as i punch it or rev a bit harder ie main jet, it gives a hug yellow (rich) flash and bogs, then comes back to life slowly and burns bright yellow, meaning its getting rid of all the fuel. i think my main is too big!!

 

[Blaner]

il keep u all posted...

 

[Blaner]

Is the slide adjusted using the top cap screw to apprx 1/8".

does this not only apply to 4 stroke carbs with an accelerator pump? i know the 450 uses this timing business to make sure the pump squirts at the right time but on a 2t, is this really necessary??

also, I have set the float. put in a a 138 (smallest i have) and moved the clip to the top groove to lean it out all i can, it feels much better but bogs in the mid range and clears nicely on main (WOT) but i feel the 138 is far to small, as the motor was really hot just from a burn around the block. will pull the plug now.

so my question is this, is the needle maybe in need of a change? does anyone know what the stock needle is for the OKO/Keihein 28PWK? im wondering if mine is incorrect...

il post some pics of the colourtune plug i was using the other day.

 

[Blaner]

ok, whipped out my needle and it is a N80F its brass is colour and has a very sharp taper as opposed to the 26 Mikuni.

i looked on the net and found that Yamaha spec (available as replacements) needles for the Keihein28 for the YZ85 are NBKF; NBLG; NBKE

does this mean i have the wrong needle?? can someone varify this?

also, pulled the plug and found the 138 is too lean as i suspected--but it runs, and still bogs in the mid meaning something is wrong with the needle?

 

[roadkill]

mine did that exact same thing with my 28mm and i couldnt figure it out i tried messing with everything on it but then i went up two sizes in the main and it fixed it completely,

 

[brandoz28]

have you tried raising the clip on the needle yet?

 

[tripleported]

I have that same oko carb. Did you purchase legit keihin jets & pilots? Also i read your mods & for some odd reason my blaster would only respond to the neddle set in the 2nd to last on the rich side & my blasty is ported to the sky lolI:I

 

[N8tsNastyBlasty]

i would start rich and work my way down.raise the needle all the way up, then go ride it, drop the needle one clip,then go ride it,drop it another and go ride it.It sounds like ur lean. to rich will sputter on top too lean will run out of steam or just kinda die off.Make sure the air filter is hella clean! if none of this works then change the main.

 

[Blaner]

put clip on top groove (lean) and it responds better and i can now get through the main where it pulls nicely and the bog gets bigger the lower i drop the clip, meaning its too rich!