Upper Screw Adjustment (after engine warm up):
Once it's nice and warm after some riding around you can adjust the idle down when you come to a stop by turning the upper screw out (counter clockwise) a little at a time while listening to how the engine responds by slowing down. Don't let the engine idle too slow because then it will take forever for the RPMS to build up for the bike to take off from a stop sign. I like mine kind of high because you don't want to be caught with your pants down out in the streets with soccer moms breathing down your neck!
Lower Screw Adjustment (after engine warm up):
Now that the bike is burning oil properly with a nice hot spark plug you can judge how well the mixture of oil and fuel is. The factory recommends 2 and 1/8 turns out but I found this to be too lean (not enough oil mixing). How can I tell? Well the top speed was only pulling up to 20mpg and then the engine would sputter and run really rough. The fuel was burning off too quickly and not pushing the complete stroke of the combustion cycle... just take my work for this if you aren't up on your combustion engine science.
So with my trusty screwdriver on a country road I backed out the screw a half a turn and hit the straightaway again! This time it ran better but STILL sputtered and spit. It sounds like the difference between a little weed wacker running at half speed compared to full throttle. You know, the wacker is sounding funky and sputtering like it wants to be given full throttle to take off. Well that's just how the 50 was running. Then I adjusted out the screw another half of a turn and the top speed increase by a few MPH as the engine sang it's note to full RPMs. I rode the Honda Express around some more roads and hills listening to the engine and making sure it sounded and ran like a good little 2 stroke. The air mixture screw is now out to around 3 turns out and it pulls 25 MPH consistantly.
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