airbox and OKO carb.

[Whitty21]

the needle doesnt have too much effect on the bottom rpm range. and as for the poping try going down a size in the pilot and turning the air screw in to around one turn out, and if that doesn't do it you were as good as u could get with the bigger pilot just my .02

 

[sicivicdude]

The keihin needle chart shows the diameter affecting from 0-1/8th throttle more than the other parts of the needle.

Check the upper right hand corner of the chart:

N427-46 Jetting Chart

If the diameter is wrong it LOOKS like the jetting with be way rich at the bottom end without the idle being off (air screw still at 1 1/2 turns out)

 

[Whitty21]

hmmm interesting, what did u use for the piiping, where did u find it btw, i think i am gunna make an airbox

 

[slickerthanyou]

I have been thinking of changing the needle myself I too run the N80F but i think i have it tuned good. Should have my motor back this week and start the break in. I had to really juice up the pilot, to get it running right (i was having surging issues when idle and less than 1/2 throttle, but a fat pilot cured that.

 

[sicivicdude]

What did you turn your air screw to to compensate for the fat pilot?

 

[sicivicdude]

The pipe is an extension piece of exhaust pipe from auto zone. I took my calipers up there to confirm the size and bought a 2 foot piece.

I noticed that the CFM box is a 2 1/2" pipe but I didn't really feel like trying to fit the 2 1/2" pipe around my shock like they do. If I were going to take the power level up above what I have right now I would purchase a CFM box. They seem to be top notch and I couldn't make it for the price they are selling it for...

I have done some more playing with my needle and discovered some very important details!

The vito's needle that I have placed inside my carburetor and for anyone else who might want to know: is comparable to a Keihin N427-46JFJ.

I shifted that needle up from the third clip and it began to sputter and down from the third clip and it began to surge. I'm convinced now I need to purchase a new needle with a larger diameter but with almost the same specs as that needle as it seems to be working fine except for being a tad rich from idle to about 1/8th throttle. Otherwise it's spot on the whole way up...

 

[slickerthanyou]

What did you turn your air screw to to compensate for the fat pilot?

I am one and three quarters out, but i need to try this on the rebuild, i just now step up to those two sizes due to the cold weather now. I also was running at 4th needle clip but dropped that down to third and will see what it does i'll have results this weekend for sure.

 

[sicivicdude]

Alright, I'm looking at purchasing new needles for my OKO carburetor. I'm understanding the needle chart much clearer now but I need some input so that I don't waste a bunch of money on purchasing unnecessary needles.

I see that you can purchase different needle diameters. I'm wondering (from someone who has ordered keihin needles to tune carburetors) how much of a difference .01mm makes? Right now at about 1/8th throttle it's actually sputtering. When I hit 1/8th throttle it all catches up and the front wheels come off the ground.

If I lower the clip it sputters worse (and the idle gets real low), if I raise the clip it gets real "surgy" like it's gone lean. So now I think needle diameter is the next step... Can anyone advise on that?