ok here is what i have so far, nothing ordered yet, i need to finish chassis work.
the mods i saw to make mucho rpm (for a lawn mower) were very simple, and equally cheap. you start with removing the governor. this takes the revs from 3600-4000ish to around 5000-5500, depending on your blocks condition. from then one would move on to heavier valve springs ($12 per set) to keep the valves from floating, as well as an enlarged oil dipper ($10) for better lubing. the springs arent necessary though. since i am dealing an older style flathead motor, floating valves does not mean bent ones, a good thing. it merely mean the motor will no longer rev for the obvious reasons. the super-duty springs keep the valves stuck to the lifters better and thus push the rpms up there a bit more.
this brings us to the next weak link, the piston rod. at this point rods start to warp or break, time to employ H-beam technology. CNC billet rods, in "H" or "I" configuration range from $45 to $75, that is super cheap. at this point its cost prohibitive for me to build any farther. but rest assured ill be wiring a tach ASAP, to record actual results.
now we are running lean, with the help of a uni filter and 12inch dumped header. for that im looking into slide type motorcycle carbs. my buddies at the shop build xr50's and have many spare carbs leftover from high perf replacements. some time next week i hope to be machining my intake manifold to adapt the two. from then on i am going to TRY to tune it with the exhaust gas monitor at work. the problem being its designed for big street bikes, but it may work. if i cant get the power or jetting i want with the xr50 carb, up ill move. the next size i see fit is an xr100 carb. the builders i spoke with recommended a 125 4stroke unit, but they are also building more than a mild motor.
does it really seem that simple? or am i missing something? i like to think that im not, however speed is never cheap. give me your thoughts guys, i need to have everything into account before i make my intake, maybe itll save me some lathe time.