Jetting a 21mm pwk carb at 164ft above sea level?

Kennen

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Hi, I'm trying to figure out whats a good jet setting for my 21mm pwk carburetor on my motorized bicycle. My elevation is 164ft above sea level. I first had a 105 then moved up to a 125 and it lost speed at least by 3-5 mph. I have a cdhpower pk80 engine, 36 tooth sprocket, 21mm carb, and the mz65 pipe replica from cdhpower. Need help. Trying to do at least 50mph on this thing 😁
 
Hi, I'm trying to figure out whats a good jet setting for my 21mm pwk carburetor on my motorized bicycle. My elevation is 164ft above sea level. I first had a 105 then moved up to a 125 and it lost speed at least by 3-5 mph. I have a cdhpower pk80 engine, 36 tooth sprocket, 21mm carb, and the mz65 pipe replica from cdhpower. Need help. Trying to do at least 50mph on this thing 😁
your probably jetted too rich, try around the 95 range and go from there, just watch the cylinder temp!
 
Hi, I'm trying to figure out whats a good jet setting for my 21mm pwk carburetor on my motorized bicycle. My elevation is 164ft above sea level. I first had a 105 then moved up to a 125 and it lost speed at least by 3-5 mph. I have a cdhpower pk80 engine, 36 tooth sprocket, 21mm carb, and the mz65 pipe replica from cdhpower. Need help. Trying to do at least 50mph on this thing 😁
I'm at about 800ft and on my 21mm I run 105 main 39 pilot middle notch on the clip. My bike hit 53.5mph last summer
 
Is it really possible to get 53mph off these 66cc engines??? That requires like 6hp..... I could understand that on a hill, but not level terrain?!

Usually a predator 212 is used to get those speeds?!
 
Is it really possible to get 53mph off these 66cc engines??? That requires like 6hp..... I could understand that on a hill, but not level terrain?!

Usually a predator 212 is used to get those speeds?!
You can, you just need a whole lotta $$

Some people are running upper 70s out of these things. (Watercooled blocks and scooter jug topend)

Also, if you regear these engines (ie 36t sprocket) you can get around 45mph with a lightly modifed engine (pipe, light port work, head shaved .020) .
 
it didnt really take alot of money. opened up the ports raised the exhaust a little bit and adde the jog scooter pipe. the biggest gains are made with a properly tuned expansion pipe
 
Thanks a lot! I've ordered more jets. Will be here Friday. I will let you know how it goes. I also noticed a leak at the intake gasket to cylinder. Ever since I changed my main to 125 the screws are backing out probably due to more vibration. Will update
 
your probably jetted too rich, try around the 95 range and go from there, just watch the cylinder temp!
Dead on with the 95 main jet. Runs, idles, starts a lot smoother.
your probably jetted too rich, try around the 95 range and go from there, just watch the cylinder temp!
Tried two jets today.
your probably jetted too rich, try around the 95 range and go from there, just watch the cylinder temp!
So far the 95 main jet is dead on like you said. My bike rides, idles, starts up much smoother. Tried 90 main and had hard time adjusting air/idle screw and with long revs when I release throttle. Put 95 back in ran just fine again. Think ima try the 98 and 100 tomorrow to see how my bike reacts to the change.
 
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