wont have a massive effect but the longer inlet will help bottom end with them fitted behind the reeds. if you make spacers for the other side of the reeds it will uncover the inlet boost port which is partially covered by the reed cage and lower the crankcase volume a tiny bit which are both things aimed at improving power at high revs. have a search for tuning tzr/tdr 250's on the net, the motors a twin which basically has two dt topends and there is alot of back to back dyno testing on things like reed spacers, cage gaps etc (just roughly half the performace gains to compair it to a dt lol)
wont be a big gain though, the problem with twostokes is everythings a compromise its easy to tune for a glob of low end power or a skinny big hp powerband but a strong all round tune is a real challenge, id hedge my bets at yamahas preset powervalve timing being the main limiting factor for this motor didn't bother myself though as its easier to cure all power problems with extra cc's ;)
ive got an ignitech cdi here where you can re-program the ignition curve and powervalve opening time curve, apparently people say the ignition retards itself too much in the higher revs even on the best yamaha cdi's and as you said the powervalve curve isnt something to brag about
if i get a laptop running windows xp to have a little tune i may set up the powervalve a bit better on my bike, that is if i dont end up selling it, ill try and get a video of it working up when i work on my bike again
starting to think you may not have needed the advice on reed spacers tom ;) your already one step ahead of the game, my friend had a adjustable cdi on a kdx200 and got good results over standard, had a switch on top of the rad cover to swap curves for the type of riding he was doing
just wanted to know if anyone had any experience with the spacers. not used them myself but i know what they are suppost to provide in terms of benefits
do you know what brand of cdi he used on his kdx?
apparently, no 2 servos are exactly alike and since the stock yamaha cdi is anologue, not digital, the PV can never ever be spot on
servos control there postition in terms of millivolts on the feedback line, whereas 1 servo may fully open the powervalve at 3150mv, another servo might fully open at 2960mv, what you can do with these ignitech units is plug them into a pc, turn the servo control off, manually set the pv open and note the millivolts it produces back to the cdi (will be displayed on pc) you can do this for when it is closed aswell and then set an 100% accurate powervalve curve
