Oko 21mm jet size for sea level

[Ceeskiroy]

Hey Guys,
I’m new to this forum. Be wrestling with the Oko 21mm Carb with reed valve on a 80cc 2 stroke. I’ve read and tried all recommendations about leaks, adjustments, etc. as soon as I squeeze clutch to disengage it stalls immediately.

I’m certain I need bigger jets. Can someone who has had success with the Oko carb on these bikes and live close to sea level share their jet sizes?

I’m in Florida 26’ about sea level. Comes with 104 main and 42 pilot. I know I need bigger because it won’t run at all if I adjust the pilot screw anything over 3/4 turn.

 

[Chainlube]

104 sounds big for a 66cc, is your plug wet?

 

[Ceeskiroy]

80cc. Not wet.

 

[Street Ryderz]

I use 45 pilot and 115 main in my 24mm oko, so I would think 42 and 105 is a good start for piston port but may still need a bigger pilot if reeded setup.

 

[Ceeskiroy]

Is there not a jet size chart for altitude for this carb? If I’m at 104 and 42 what size up should I try next?

So many people saying you have to know how to tune these but zero info on jet sizes. Does knowing how to tune it mean throwing random jet sizes at it until something works?

 

[Karl Snarl]

Is there not a jet size chart for altitude for this carb? If I’m at 104 and 42 what size up should I try next?

So many people saying you have to know how to tune these but zero info on jet sizes. Does knowing how to tune it mean throwing random jet sizes at it until something works?

You could tune by jet if you knew cfm of engine and fuel needs. Them match to a jet with the proper flow rate at said cfm's.

 

[DieselTech]

Look up carburetor fuel correction factor for keihin carbs, it explains jet sizes based on a formula for elevation among other factors.

 

[Ceeskiroy]

Will do but for now if I’m at 104 main 42 pilot what would be the logical size up to try?

 

[Street Ryderz]

Will do but for now if I’m at 104 main 42 pilot what would be the logical size up to try?

I'd try the #45 pilot, it's much easier to clean up (correct) being a bit fat then being too lean, 3/4 of a turn on the air screw is very lean as it should be out around 2 turns.

 

[Ceeskiroy]

The little screw for the WOT adjust fell out while driving. Does anyone know where to buy this for this carb? Will it not start with this missing.?

I’m bout to chuck this thing. Anyone know a hassle free carb to use with the reed valve?