as some will know i have purchased daz's horrendous luminous orange peugeot speedfight ped as a base for next year's monster... what's been done to it so far is a good starting point currently, with the mods daz has done on it and the set-up, it runs ok and will go off the clock easy, but you know me, i cant leave fk all alone & will not be satisfied til its power wheelying and topping out at a ton+ anyway. today i was bored. i took the top end off and had a look at the squish band - sorry if your not au fait with 2 stroke talk, - thats the distance between the piston crown and the combustion chamber of the cylinder head. this is easy to measure by poking a bit of solder down the plug hole and kick it over, then measure the flattened solder. I was quite surprised to see it was over 2mm! :O ive had good results before by reducing this down to 0.030" (30 thou) so being a rough arse, i set to it with an angle grinder then filed it flat again to a .5mm gap which is about 20 thou. with the gasket it should be where i want it more or less. it still needs lapping flat to the cylinder with grinding paste but it's getting there... (i got laughed at last time i did this to a 70cc bike but it did over 80mph when i'd finished so stfu lol!) next job is to examine the port timing, and widen the transfer ports and exhaust ports. for best results i'm looking at setting the transfer port timing to 130 degrees duration & exhaust port to stay open 190 degrees. this is more or less the optimum for a reed valve motor and while it will lose a bit of bottom end torque & need a higher idle speed, this isnt really important on a motor that doesnt pull off under 5k anyway, unlike a geared bike but it should let it rev nice to about 14k rpm looking at the guys who are racing these on the track & drag strip, the best way to obtain this timing (with a standard barrel) is by using a 2mm base gasket then taking 2mm off the top of the cylinder.... then raising the exhaust port a further 1.5mm. obviously with the polini cylinder thats fitted, i will need to measure the timing before deciding how much to take off otherwise it will run like a bag of fk! i cba stripping the crankcases atm as its just been done, but at the next rebuild the balancing holes in the crank will be getting packed with cork & rebalanced (massively raises primary compression) and also i'll knife-edge the ports and piston skirt, match up the piston ports to the rear transfer ports and give it all a good polish..... most probably just run the top ring the idea is to move most of the power right up top and make the engine breathe better at very high rpm... something its not doing atm. love 2 strokes me i'll add some pics as it progresses and hopefully get it on a dyno when im happy with it!
That's it I'm going all the way with my new project, fkd if I'm letting my own stroker beat my new version. Martin best you do a good job cos the gauntlet is thrown down I've just been speaking with Dave Wood and he's gonna get mine to the max by properly tuning the barrel and sorting out the squish. Game on OH AN WHATS WITH TH UGLY THING ?????
here yer go daz... theoretical max 21bhp @14000rpm. but look at the size of the carb it needs to get that lol!!!!! ive got a 24mm jobby that i can use but that only pushes it to 19.5bhp lol (to put this into perspective, the regulations for 50cc ped racing only allow a 12mm carb!) this also comes very close (well, just over) the maximum piston speed i can get with the conrod without it self destructing! mwahahahaha i'll try & upload the software if i can daz, basically whip the cylinder off, measure the port heights etc, fill all the boxes, set max rpm, set port duration and the software does the rest. its easy to raise the exhaust but to jack the transfer & boost ports just make a spacer with a base gasket either side *ah it wont let me upload the software! was going to say use the v4.42 cos its a bit easier to use. never mind m8 youll have to settle for smelling my smoke
I foresee a lot of smoke and a piston lodged in Benny's torso. Remind me to stay well back if I ever see you on that ped!
m8 you will be well back lol Some nice stuff here i dug up from 49ccscoot.com in particular this timing wheel - absolutely priceless tool for tuning these engines. i'l print this off and laminate it onto a card... unless someone with a cd printer would be kind enough to laser print it onto a blank cd pretty pls
was the electrics that let it down m8 and the shitty standard carb... i shouldve stuck with the slide carb id put on it and it wouldve been ok... apart from the stator burning out, which tbh couldve happened any time! this one WILL blow up lol... i have absolutely no doubt about that... but it wil be so easy to put back together, as you saw with bens. my old 2t 125 race bike used to eat a piston every 200 mile or so & i rebuilt the crank every month. i'll be lucky to get 1000 mile out of this engine before a rebuild, but only if i wring its neck everywhere... standard these things put out 3.5bhp and im asking for over 20... its inevitable really lol!
how to use the dial gauge here.... http://49ccscoot.proboards.com/index.cgi?board=yamajog&action=display&thread=353 many thanks to 90GTVert for all this info - hope it is of use to some here
at the back you say i was never with a nearly standard ped hahahaha mine is only getting upgraded with subtle parts inc. 2 ring piston i (THINK) i want to make the whole jurney AGAIN!!!!
wants it running like this lol... http://s639.photobuc...103firstrun.mp4 yeeeehaaaaw :/ nice shoes btw!!! thats sleeved to 103cc with same port timings as i stated earlier for mine... looking at the barrel on mine though, its only got 5 ports.... the one i raced had 9 lol... so thinking of swapping the cylinder for one off an 80cc crosser & see how it goes. will have to do a fair bit of machining like but will be worth it oh & the bigger carb ive got went straight on
started off as a 50 then was opened up to 90cc then finally went to 103! the guy who built that is a bit of a hick like but a sh*t hot engineer and knows his 2 strokes. bit of an update on the pug.... i took about a mil off the head and put it back together... it runs a hell of a lot better - but it ran even better still when i thightened the spark plug up lol. fk nose how it started before lol!!! anyway i couldnt see what i was doing proper to draw a proper port map & measure the port events so i decided to whip the motor out and do it properly. looking at it closer, the stage 6 reed block is a p*ss poor match to the intake recess and there are way too many sharp angles in the casings... the squish was still 1.2mm even after grinding what seemed like loads off the head, the piston stops 1.4mm into the cylinder and doesnt clear the transfer and boost ports at bdc so it will be getting a 2mm base gasket & 3mm off the top of the cylinder... that should give me near enough the timings im after, and the casings will be mtched up as near as i can go... i'll do a before and after on this as it comes along... currently the cylinder, head & piston are soaking in degreaser ready for marking up i'm aiming for a theoretical compression ratio of about 16:1, which in reality is only around 7:1 after the exhaust port closes. might also slim the flywheel down a bit and lose a pair of magnets
been busy! currently it's got a 47mm (67.8cc) polini barrel & piston which on an otherwise stock ped will take it to 8.5bhp. looking closer, it had a squish band of 2.1mm, which should ideally be about .6mm (and the plug was loose, which doesnt help - plus, looking at it, i dont think that's the correct reach plug anyway!) so i set to the head to remove the 2mm lip under the squish band. finished article: next onto the porting... comparing this with what ive used before, this is a relatively low power set-up and is designed to give a broad power band peaking about 8k rpm. with the full circle crank that's fitted, im looking for peak power between 12 & 14000rpm! 8O port mapping: this looks very similar to the polini corsa sports cylinder but the boost port on mine is a bit bigger. the underside.... theres a few gains there by removing the sharp edges and making the ports deeper, particularly the boost port at the rear which is only about 6mm deep! i'll run with this cylinder for now as its nearly new but ive got a stage 6 ally cylinder coming from usa which has an extra pair of transfer ports and twin bridged exhaust ports so should have higher potential with the right timings... i also noticed that at tdc the piston is 1.5mm off the top of the cylinder so i'll probably remove the lip before i make any port mods. i could cheat and fit a spacer under the barrel to raise the boost ports a bit, but this would mean taking even more off the top & i reckon i'd get problems with sealing to the head if i remove all the lip? its also fitted with a stage 6 induction kit with a massive reed block, but it's a p*ss poor fit in the reed recess in the crankcase so the motor will have to come out for some crankcase mods and port matching. there's lots of other sharp bits in there and unnecessary bridges that will be getting ground out & polished once the motor's out & cleaned up i'll fix a timing disc to the crank & get some proper measurements. i know roughly what durations i'm aiming for but the rest will be trial & error! ordered up a 26mm flatslide carb today to replace the 19 round slide thats on it atm in all im looking to achieve a true 16-20bhp out of this engine which is well doable but close to the limits on an aircooled engine. should keep me out of mischief for a while eh!
Wow benny the super duper moped engineer!!! Fancy telling me how to tune my little ped? only want 55mph out of it realy
How!!! Can someone just tell me what to buy! not after a rocket machine like you guys just want a little faster but reliable Need an exhaust so any ideas?
just put a decent 70 kit on it and shop around for a nice exhaust... dont just go for looks though, you want a good fat header on it or it wont rev high enough
