24mm oko, pg long, nikasil 78cc BBK, what jetting?

[bakaracer]

Also with these carbs,2 turns out is the starting point. If you are more than 1/2 turn out then the pilot is to rich. If your less than 1 1/2 turns in then your pilot is to lean. Adjust the air fuel and needle adjust ments together so if you adjust the needle then check adjustment on the air fuel screw too.checking where it idles highest is not always the best air fuel adjustment.

[steffen707]

Hmm, i was afraid of that. Normally i don't ride at 1/2 throttle. Usually its WOT until i get to my desired speed, then I back off to maintain that speed, but for break in I can't do that.

I also noticed that while it doesn't accelerate as good at 1/2 throttle from 0to 25mph, once you get around that mph, it starts making good power and then wants to speed up faster than 25, onto like 35mph, so I have to back off the throttle to 1/4-1/3 and it will maintain 25-30mph, where as before it hit 25mph, it didn't feel like it had enough.

Sorry if my explanations aren't very clear. Its hard to keep an eye on my throttle, speed, what the engine sounds like, all without breaking many traffic laws.

[steffen707]

Also with these carbs,2 turns out is the starting point. If you are more than 1/2 turn out then the pilot is to rich. If your less than 1 1/2 turns in then your pilot is to lean. Adjust the air fuel and needle adjust ments together so if you adjust the needle then check adjustment on the air fuel screw too.checking where it idles highest is not always the best air fuel adjustment.

Baka, when you said if you're more than 1/2 turn out the pilot is too rich, and if you're less than 1 1/2 turns in then your pilot is too lean, what is the starting point you're referring to, (2 turns out?)

So if I'm more than 1/2 turn out from 2 turns out= 2.5 turns, then i'm too rich? Do these carbs have an air screw, or a fuel screw? I read most 2 strokes have air screws, and air screws act opposite of fuel screws?

[steffen707]

i know you said anything past 50 on the pilot is too much, but when i turn the air screw all the way clockwise the bike still idles fine. I thought I read if it doesn't become eratic, then the pilot is too lean?

[bakaracer]

These carbs have air screws. So turning the screw counter clock wise, your letting more air into air fuel mixture system.anything past 2 1/2 turns out(counter clock wise) your pilot jet is to rich. If you have to turn the screw past the 2 1/2 turn mark to lean and match the big pilot your to rich on the pilot. If your less than 1 1/2 turns in(clock wise) then your pilot jet is to lean. If you screw it in past that point to close and the bike is still at idle without dying then you have a intake leak somewhere. Hens why also you had to keep going up on the pilot. Also the keihin clone carbs sometimes tend to run lean too. That's why I either use keihin or mikuni carbs. Much more consistant in craftsmanship of the carb and the tuning seems to be more consistant too. Try and borrow someones keihin carb and see if your jetting issue is still there.starting point jetting is going to be the same for the 24mm carbs except for a mikuni which uses a different number to hole size number.

[steffen707]

These carbs have air screws. So turning the screw counter clock wise, your letting more air into air fuel mixture system.anything past 2 1/2 turns out(counter clock wise) your pilot jet is to rich. If you have to turn the screw past the 2 1/2 turn mark to lean and match the big pilot your to rich on the pilot. If your less than 1 1/2 turns in(clock wise) then your pilot jet is to lean. If you screw it in past that point to close and the bike is still at idle without dying then you have a intake leak somewhere. Hens why also you had to keep going up on the pilot. Also the keihin clone carbs sometimes tend to run lean too. That's why I either use keihin or mikuni carbs. Much more consistant in craftsmanship of the carb and the tuning seems to be more consistant too. Try and borrow someones keihin carb and see if your jetting issue is still there.starting point jetting is going to be the same for the 24mm carbs except for a mikuni which uses a different number to hole size number.

I don't mean to beat this to death, but I get when you say turn the air screw all the way clockwise, now if I turn it past 2.5 turns counter clockwise (from bottomed out clockwise) to lean out, that my pilot jet is too rich.

What i'm confused on is when you say "if you're less than 1.5 turns IN (clock wise), "from where?" Did you mean if you're less than 1.5 turns OUT, from bottomed out all the way clockwise?

So if i'm from 0-1.5 turns out(counterclockwise) from bottomed out (all the way in clockwise) then the pilot jet is too lean?

Did I read correctly that the best way to find an intake leak is to spray carb cleaner around the intake, carb, and rubber intake/carb connector? Then if the engine changes its idle its sucking in carb cleaner through some leak, then I need to find the spot where its leaking in?

[steffen707]

i know you said anything past 50 on the pilot is too much, but when i turn the air screw all the way clockwise the bike still idles fine. I thought I read if it doesn't become eratic, then the pilot is too lean?

I went back and tested this last night, and I was wrong. I wasn't letting the engine run long enough after turning the air screw all the way in. Last night when i turned it all the way in and let it sit for 5 seconds or so, the engine did die.

[bakaracer]

Sorry its if your less than 1.5 turns out from 0 then your pilot is to lean. Starting point for these carbs is around 2 turns out +/- 1/8th of a turn

[steffen707]

Sorry its if your less than 1.5 turns out from 0 then your pilot is to lean. Starting point for these carbs is around 2 turns out +/- 1/8th of a turn

Lol, no problem, just wanted to make sure I was understanding you.

[steffen707]

I finally understand what was meant that the trans and carb need to be tuned together.

I'm going to post this in the other thread I started about more of the tune as well. To some of you guys this will probably sound stupid and elementary, but IÔÇÖm hoping somebody like myself that reads this post in the future can save some headaches.

I was having 1/8-1/4 lean condition as well as a rich bog issue around 6000rpm. I was kinda chasing my tail with making one thing better but screwing up another at the same time.

I read something on another site and it dawned on me, with the PG long I wasnÔÇÖt making any power under 6000rpm, so with the advice from lots of you I finally tried tuning the trans. I ended up breaking the clutch springs that I had on the scooter from before because I couldnÔÇÖt get them off. I put on some (what I think are 2k) clutch springs. My fianc├® doesnÔÇÖt know where her kitchen gram scale is, so I left the roller weights in and took the scoot for another ride.
Now the clutch engages right around 6000-6500, and I donÔÇÖt have the wussy no power lean situation I was getting when it was engaging at like 3500rpm. Also the bog issue around 6,000 is almost eliminated. The scooter is driveable and fun. I need to tune the roller weights and possibly change the 1500 contra/center spring so I get into the 8500+ power range because thatÔÇÖs when its really hauling.

So the moral of my tuning dilemma is that, I should have gotten the carb to run decent, then tune the trans to the desired powerband, and then go back and fine tune the carb if needed.
Thanks to all of you that have given me tips and advice. This scooter is so much fun now, and its not even fully tuned up.

[Fishman43]

So what was you final jetting numbers and needle setting?

[steffen707]

Well currently its a 50 pilot 120 main, 6kb needle one clip down from top, no air leaks and air screw 1.5 turns out, 2k clutch spring.

I think I have a 1500contra/center spring and unknown roller weights. I need to weigh them when I find the fiances kitchen scale, then tune the rpm better and then I might revisit the final carb settings.

[steffen707]

Hey guys! I'm back for my 1 year update. :p

When I first did this build I was chasing my tail with the jetting. I had a lean condition and a rich condition verified by my wideband o2 sensor in the mid range. It was very annoying.

Bakaracer and others on here helped me tremendously, and I turned to the trans. Put higher rpm clutch grab springs in, and that helped a lot because it took off at a higher RPM; however, at mid speeds it was still only reving at about 6000-6500 rpm. This was with 54 grams weight in the variator. I then tried 45 grams and HOLY COW, that stumbling from 20-35mph was gone, and i was making about 7,000 rpm at those speeds. For * and giggles I tried 36 grams (thinking that would be way too low).

What a difference, it now takes off like mad from 0 and climbs until the needle is buried. No stumbling or rough running. If you back off the throttle at any speed and get back on, it quickly climbs back from 7500rpm to 9000+

I think I have 9:1 gears in the scooter, but I maxed out at about 11,100rpm and GPS said it was 57mph.

It feels like it has more power to go faster if I had different gears. I think years ago I bought 9:1 and 8.4:1 gears. Might have to swap those in.