Jetting Help - 21mm OKO/Corsa/Scorpion

[burnt_toast]

Hi everyone, long time no see. Trying to retune my main ride and I could use your advice. What is the best jetting combo you guys have had with 21mm OKO, open UNI, and 72cc with a high-rev pipe?

Currently running a well-mileaged Polini Corsa (5k+ miles) and recently switched over from a YMS street to the Scorpion exhaust. Ideally if you have the same and 21mm OKO with open filter PLZ plz chime in! <3

My best with the YMS was:
110 main
52 pilot
mid clip
1.25 out A/F

The same combo works decent with the Scorpion, but could def be improved. Choppy in low range and clears up past mid, with good top end pull. Plus CHT temps approaching 450F, about 100F hotter than with YMS.. CVT is mostly sorted with ~42g total, and I'm more-so concerted about jetting with this post.

Next step up on main (on hand) is 122 and that was WAY too rich. And next up on pilot 55 only made things worse.

Currently on 4th retune attempt, but honestly still boggy in mid and low. Will see how CHT temps improve on longer ride tomorrow.
Currently at:
110 main
45 pilot
+1 rich clip
1.25out A/F

Help a brotha out yall

[Downsouthdio]

Drop both jets.one at a time..102-105/40

[burnt_toast]

uhhh and run lean??

doesn't make much sense.
Also doesn't make sense that Scorpion pipe would need LESS fuel than the basic YMS. recall i am running 100deg F hotter now than before...

[Downsouthdio]

Mis read that sorry

[1man8scoots]

45 pilot is what I ran in a 24mm oko. Sounds like you need to buy some jets. The scorp liked 5 jet sizes bigger than a fabrizi chamber so I'd imagine the yms to scorp jump will be similiar.
Also the scorp loves light rollers. 36g is the max for a scorp if you want real power.

[burnt_toast]

Good stuff. Yeah I think 115main might be the ticket for the top end. but dam if 24oko took 45pilot seems i may indeed want to drop that. guess i can try that in meantime

And good call on the rollers, plan on messing with that once i upgear to 8.4, running out of room with the 9s...

thx for advice

[burnt_toast]

Just a small update, but pretty noticeable improvement in CHT by just going +1 clip richer on needle, and keeping 110main and 45pilot

About 50deg F temp drop with 400F on high end, and 300-350F cruise temp.

Was going to source a 115main, but may just try dropping pilot some more and see how low end clears up. Roller drop to 36g may help too.

On an aside, I ran my YMS jet setting with the Scorpion for a pretty considerable distance, and pegged out with 450 F temps, with no problems. I mean I'm talking long distance WOT pulls, and several hwy jumps. Polini Corsa is one amazing top end, just a shout out

[Downsouthdio]

Thats on the edge,dont want to take it
THat high to many times

[burnt_toast]

Thats on the edge,dont want to take it
THat high to many times

Oh heck ya, totally agree. I was riding and expecting it to pop, but nothing, just kept on trucking. <3 Corsa

Had issues with my red bike and Corsa at ~425F, but this ones got 5k+ miles and was broken in real well, lots of heat cycles so maybe its just more stout. Was good to know it could take it

[burnt_toast]

So after about 10jetting combos it still runs like s*** in the mostly low range, then clears up after 20-25mph

115main seems okay, but dam that low end bog! still there w/ either 42pilot or 55pilot. have tried all clip settings too, not much help

Anyone else have a good baseline to start with?? Like what has worked for you w/ Scorpion & 21mm??

Going to try a new center/grab springs, and Naraku manifold, but think Im going to restart all over on the jetting..

[Wheelman-111]

Greetings:

Daytona has a needle collection that can clean up the low end with educated guesses, judicious choices and yes, trial and error. Figure out if the lousy low end is due to rich or lean, and adjust but choosing thicker or thinner needle in that segment. Corsa typically just sucks below 8500 regardless. Remember "Corsa" means Race. Not friendly for suburban city street riding.

[52much]

I had a lot of problems on the OKO getting the bottom end to work. I tried every combination pilot, air bleed adjust, idle adjust, I could. Even on multiple af16's. By accident I tried a Pollini. And everything straighten out. I couldn't believe the difference. I felt like I finally got a motor/ carb that was tunable. If you get the OKO to work, I'd like to know the fix. Because I have about 6 OKO's with no bottom end adjust.

[burnt_toast]

thanks guys. shelved this prj for the moment so i could focus on other bikes.

got some trans parts in that should help, and i may try the needle idea. plus got a naraku intake manifold, maybe it'll help with flow better than the ct and also effect things (hopefully with positive results).

i do remember dialing in my red bike w/ Corsa and a 28 OKO but it tooks LOTS of trial and error to get it just right

[benji]

Try the needle jet. That really is what the bike runs on most of the time. There's a whole world of needles and how they transition from idle to 3/4 throttle. It's really where the tuning is, imo.

[MrJumps]

ALSO, if you didn't sand down your ct, there is a 90% chance its leaking. If your over 390 at any given time you have issues. I haven't been able to break 380, no matter how lean I go on my "non oko". Last oko I had was a nightmare to tune, and it always ran hot, with crappy starting and terrible transition.

Just cleaned up my ct today and its night and dy difrence