120cc stroker jetting need help

[Af16eArnadaHI]

Hey wassup everyone need some help on jettin my 120cc stroker cant get it right its a s block 52.6 crank 54mm bore got a 28oko carb jets is 135 55 keli pulley 45grams zx trans w/keli heavy clutch 1500 center 3000 clutch carb needle is set in the middle I do have 30mm oko carb that I havent use yet if I do use what would be the jettin on that also needle settings thanks for your help

[kingkamehameha]

No one can give you a magic formula. You gotta learn to read your motor and tune. I would start with huge jets and work your way down. I would try a 142ish main and you
Might need a bigger pilot

[Wheelman-111]

Greetings:

With that much displacement, I'd start with no smaller than a 160 main in the 30 and watch closely; it still may be too small.
Pilot might like 55 or more. Take 10 off the main and 5 off the Pilot if you opt for the 28. This is from my limited experience and short-lived 90cc mini-stroker, so it's conservative.

[Af16eArnadaHI]

Greetings:

With that much displacement, I'd start with no smaller than a 160 main in the 30 and watch closely; it still may be too small.
Pilot might like 55 or more. Take 10 off the main and 5 off the Pilot if you opt for the 28. This is from my limited experience and short-lived 90cc mini-stroker, so it's conservative.

Thanks wheelman ill try it

[kingkamehameha]

The theory is that bigger displacement will suck more fuel thru those jets than a 70cc. You might not be too far off with a 140-145 main.

[Wheelman-111]

Greetings:

Bigger displacement - for a given high RPM at full throttle - draws a higher volume of mixture.
Despite the higher level of vacuum in the carb throat, flow rate through the jet is limited by fluid dynamics fizzikz to a greater degree than the mixture (air) blasting through. Little jets won't keep up enough spray to match the higher air volumes. With respect, bigger bore needs bigger jet or it runs hot and burns.

[Af16eArnadaHI]

I decide to go with the 30mm oko an got some bigger main an pilot

[Trafficjamz]

The theory is that bigger displacement will suck more fuel thru those jets than a 70cc. You might not be too far off with a 140-145 main.

I have found this to be true if a similar pipe is used.

what pipe are you running on your stoker?

[Af16eArnadaHI]

The theory is that bigger displacement will suck more fuel thru those jets than a 70cc. You might not be too far off with a 140-145 main.

I have found this to be true if a similar pipe is used.

what pipe are you running on your stoker?

Whats up trafficjamz im using a pg copy replica pipe...right now also jetted to 62 pilot and 160 main an I can feel that my main is a lil too big correct me if im wrong..btw when carb mani comes hot does that mean anything thanks again

[Trafficjamz]

That main sounds too big to me.

But, a hot manifold usually means your running lean.

[Af16eArnadaHI]

That main sounds too big to me.

But, a hot manifold usually means your running lean.

Ok I dropped the,jets to 60 158 opened the air mix half turn out so now mani is sweatin,now

[Wheelman-111]

Greetings:

Manifold, schmanifold! What's the CHT say? What does the plug look like? All intakes feel cool running. Don't go by that to determine your jetting.

[Af16eArnadaHI]

H

[paulpauly7]

put a new one in and do a proper plug chop

[Af16eArnadaHI]

put a new one in and do a proper plug chop

That was a new one but I can put another new one