jetting questions

It's unlikely you want to go much leaner than a .60 jet.
however the jet may not be accurate.
Getting a set of jet drills and a micrometer is the go.
then soldering and redrilling isn't hard.
Piston however should be black.
Colour of plug will tell more.
Is it 4 stroking?

Blocked fuel filter, petcock or tank cap vent?

That sounds like your problem.
may need to drill a small breather hole.

I wanted to make a very intelligent suggestion to some folks experiencing the joys of the cheap 2 cycle motors bogging down and or vibrationing after certain throttle points. A lot people that are experiencing this mystery could possibly have a total of 3 problems all at once not even related to the carb or jetting. One is the magneto being junk develops a short loose ground or gets fuel soaked. It tends to want to 4 cycle. The mag eventually fails. Read about the exhaust please read on...........

The other problem I have noticed is the Throttles themselves like the ones Bike Berry sells with the real cheap Chinese kits. The cable itself is almost a 1/2" inch too long. The engine can not achieve idle and if it does usually it's by gods good luck or making the engine idle with the throttle itself. This makes junk out of a good carb. The Carb it'll soon start flooding and ejecting fuel out the airport/aircleaner. Not a pleasant surprise but when the engine doesn't seem to sing those high notes or surges vibrates nine times out of ten it's the throttle position and the magneto sensing that excess fuel load VIA the plug not firing getting fuel soaked as well then it starts to 4 cycle eventually either the mag itself stops working or the carb itself self destructs. Usually it's not jetting at all. Another thing that helps a lot of this nearly eliminates this problem from square one is to cut off the TUBE STUMP at the bottom of the exhaust tube take it apart and drill out that baffle tube completely remove that tube that sticks up from the bottom of the exhaust. Remove the nut or screw and drill out that pipe. Get rid of it. The engine will come back to life on it's own start digesting the fuel IF YOU USE A NEW MAG PLUG WITH THIS TRICK and don't forget to check that throttle cable length too... It is the reason us Stock Car people do not put mufflers on our race cars. The compression fuel and valves would LOAD THE ENGINE UP WITH FUEL OR FLOOD OUR CARBS it's too much back pressure restricting the engine. When your engine can't jettison that excess fuel it loads up bogs down effects the mag the plug and eventually STOPS YOUR FUEL FLOW...

Iv,built six and they all needed rejetting 60 to 62 depending on mods to exhaust and intake. The cable length doesn,t affect idle at all it,s controlled by the screw on the side of carb when its screwed in it lifts the slide .The mags are junk though and a provision to accurately set and adjust ignition timing would help.

To Raydog

I can take you word for word, I believe some people have solved their issues with this re-jetting. By the mechanics of all it the exhausts are too restrictive that would lead to a .45mm jet being too large at some points or too small, gas quality matters a lot to these engines and all other 2 cycle motors. But as the engines break in they do seem to require LESS fuel. Then there is gas quality which can be like a yo yo in the northern regions of the U.S.

No argument on the point of the mags or some way of setting spark timing. Should they start using an electronic CDI to control spark that is an idea. Thee most common problem here is the exhausts restricting flows. The engine with a restricted pipe can obviously take in more than it can exhaust hence going the round about way with smaller jetting may have solved issues. The potency of gasoline in different regions is also another real issue. The gas quality where I live is usually good however there are times I have gotten gas and had it bog the engines down. The engines I own and run around with. It is a really frightening scenario. Adjusting the idle screw sometimes just makes matters worse. It just seems 93 octane isn't really 93 octane at times.