new 80 cc motor kit no power only goes 15 mph

bought 2 motor kits from bikeberry 80 cc installed them and the motors have no power and only go
15 mph thought it might be the carbs but put one on from another bike that runs good still the same.
what could be the problem?

got the fuel to oil ratio mix right 20 to 1 or 32 to1?
4 oz. of oil to 1 gallon of regular gas for 32 to1 mix.
will the throttle slide open all the way? do you know which way the choke is on and off? lever up choke is on lever down choke is off.
spark plug gap is it at 0.020"
I don't have a lot of info to work with.
new engines take a while before they run good they need to broke in first and will sometimes run crumby until they are broke in.

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norms-iron-works.tripod.com

fuel mix is 20 to 1 choke is off have built these before and never seen this happen no power and will rev up but not when you release the clutch.
it has no power by the way both motor bikes I built have the same problem

when you rev it with the clutch disengaged ther is no load...is something on the bike binding???if you pull the clutch cover can you spin the output from the clutch pressure plate???is the motor ok? break in sometimes takes a bit...is the exhaust clogged...try taking it off...should have big low end...was the intake gasket cut right?(kinda unlikely) try breaking it in for 1/2 a tank and if it doesn't start getting anymore power then you got something wrong

All these motors run like absolute crap for about the first 200mi or so, 4stroking (firing ever other round instead of each compression stroke) - this will go away once its broke in and it'll be like an entirely different engine.

Although 15mph seems a touch slow even for a new motor - I'd go through the sys and make sure everything's proper, but don't be too worried about it if it's still 4stroking - that's "normal" lol

Bikeberry is a good company and if you got the Grubee - odds are the motor is fine.

mine did the same exact thing and had no torque(power) after releasing the clutch. i bought a new top and bottom gasket for the cylinder. made sure the spark plug was at .20 gap(make sure to upgrade to an ngk). new fuel filter, cleaned the carb after new filter and all this made a huge difference. o and when 28 mph wasnt enough i put a touch of rc nitro in the tank.... just to give it that zip.

in the end i think your problem is most likely in the compression or the carb not feeding enough fuel once under load.

o btw my bike is running like a top now

if you need any more help or need to know something just let me know.