it wont fk up daz. been measuring and calculating this all week lol and trust me m8... another 10hp+ for 20 quids worth of piston kit and a rebore. plus with making the bore oversquare it increases the rpm to 11k. atm its only revving to 9000rpm tops.... peak power before i started on it works out at 8500rpm. and at that rpm it was doing 63mph on the sat nav. so i reckon at 11k it'll be close on 80mph and will get there on one wheel lol if, and i mean if, the worst happens.... ive got a slightly used airsal ally 70 kit on its way from america so alls not lost. but as i said earlier, ive done this before on cast barrels and its a piece of p*ss m8. trust me lol. also... to do this, you need to get a fkt up big bore kit thats scored to fk, then let me loose on it with the porting tools & dial gauge, then take it to gramps & get it bored out. no point buying a new bbk to throw away the piston and grind the arse off it. you know it makes sense. do you want to ride a 40mph moped or an 80mph drag racing scoot lol. you can still ride it at 40 if you want.... but instead of caning the nackers of it you'll only be bimbling along.
FOUND THEM CHEAPER HERE - http://www.ebay.co.uk/itm/Piston-Kit-Suzuki-GT185-FR80-CP80-CS80-/380396179258?pt=UK_Motorcycle_Parts&hash=item5891610f3a lol at ped with a gt185 piston in it changed order +2.0MM oversize = 79.9CC, just in case i need to rebore it in the future, still got 2 oversizes left! recalculated, reducing compression to a safe 7:1 which should be nice & tractable, gives 18hp at 9500rpm, which tbh is a bit more like it, for reliability like.
oh yessss. let the fun begin new piston kit arrived today, and some other goodies i'd ordered... left... a 40mm piston (off my 4t but same size as std pug bore) middle... 47mm polini piston from 70 bbk right - 51mm piston from suzuki gt185!!! as you can see, i need to trim 8mm off the skirt of the new piston, and machine the crown a little. the old piston stops 1.6mm short of the top of the bore so i'll set this one flush & recut the cylinder head to suit the dome crown. the top ring will run right where the old piston crown stopped. i'm guessing i'll have to run this on 97ron lol! good thing is the ring stops are in the right place so i wont need to move them like i did the last time i did this - 30 yr ago lol! may need to weld up the cylinder inside the boost port a little as the skirt will only be .7mm thick after i bore it out another 2mm off the radius. (not that this matters much but im just bothered about expansion) also my new dremel arrived with pencil flexishaft so i can get on with matching the cases & drilling the new oilways
phew! after much filing and dremelling the new piston is something like.... cut the skirt down to match the old one but haven't cut the piston port yet, until the bore is done and i can match it up properly. took 1.3mm off the crown, leaving it 1.2mm higher than the old one so it reaches the top of the bore... need to dish out the head a bit though - i'll do that tomorrow. the new piston is quite a bit thicker than the old one... hopefully it doesn't affect balance too much! i took the square edges off one side but i've got no skin left now lol.... i'll finish it all off tomorrow then drop the cylinder off to get the +4mm rebore done i just got told i am insane for putting a gt185 piston in a 50cc scooter lol :lol:
called to see my tubby m8 (well, one of them lol!) tonight & came back with a set of minarelli vertical a/c cases, variator casing with cnc cut vents, gearbox assy, loads of shafts, cables, calipers, loads of goodies - cheers m8 but mainly.... another polini head, this one with o-ring seal and very low squish - incidentally this one takes the short reach plug, just to confuse the issue! thing is with this one, the o ring is 51id x 55od which means i wont be able to use this head with the bigger piston or the new bore will cut into the o-ring & burn it away in no time. i'll use this as a spare with the 47mm kit that's on atm & use the gasket type polini head with the bigger piston - it'll mean re-cutting the chamber but there is no o-ring to worry about also got another 47mm polini cast cylinder.... looks to be a corsa but i'll find out when i map the ports tomorrow - not as badly scored as i remembered this one, i reckon a scuff with p600 will see it right. and one used ported polini 47mm piston with no rings or pin.... and a brand new one with no piston port (yet) but 6mm shorter skirt & Much lighter... also has copper moly plated rings.... i slotted the new piston into the bore with the plated rings and it's absolutely perfect. so i now have a dilemma... which one to bore out to 51mm lol! i want to get this done this week so i can have it all together for next weekend and give it run in... also debating whether to add some additional cooling? what im thinking is, ive got a spare vtr1000 rad fan (9" blades) and it just fits under the seat.... im considering cutting some ducts under the seat to either blow in extra cool air or suck out heat.... these fans move a hell of a lot of air so i reckon it will work fine. thing is though i was planning on adding an aux fuel tank under the seat to improve the crap range of the scoot - it only holds about 4L of fuel and that wont get me far with the 80cc kit! i'm thinking i dont want to be drawing hot air out across the aux tank so it'd probably be better to force cool air in.... ideas on a postcard please! *ws also discussing with my mate about side mounting the carb..... he's planning on using a 24mm flatslide off a ktm 80 while i have a 26mm roundslide keihin. both have deep bowl so fitting conventionally behind the reed block is a problem. but as it happens, the carb block on the stage 6 reed block we both have can be turned through 90* so it's possible to mount a bigger carb with the air intake facing the left of the bike... so... whether to angle an air cleaner back toward the shocker or just fit a bellmouth on it with a gauze to stop furry animals getting sucked in. fine dirt / dust getting in shouldnt really be an issue as i envisage this engine getting a rebuild at least every 1000 miles.... ideas? opinions? yes i know the jetting will be a pain!
ohhh yessss. now we're cookin!!! it is done. 86.48cc decided to leave the cheapo taiwanese piston and instead went for a 53mm mitaka suzuki gt185 piston kit and bored the 47mm cylinder out a further 6mm. the spigot is now about as thin as i dared go, and also the bit of the cylinder behind the boost port is wafer thin. hopefully it wont be a problem. the guy who bored it for me kindly recut the boost a bit deeper, as opening out the bore i lost a bit of height on it due to it having quite a chamfer. still got a bit of port work to do and also got to mod the head to take the wider bore and domed crown. got some platinum bearings as well... and a couple of base gaskets to sandwich the ally spacer i made. can't wait to get it all together & have a go! next step is to fab up a stand-off plate for the big carb, and remap the port timings so i can measure up for a new diy exhaust. i plan to limit the rpm to around 10,500 with the design of the can so it doesnt rev to the 11k ring flutter point. might last a bit longer lol!
last night i recut the exhaust port to 65% cord with same profile as the 47mm cyl that's on atm.... (the blue is for marking and checking piston - head contact points) today i spent all morning recutting the cyl head to match the new domed piston the difference in the piston crown is quite extreme!.... . (they're both polini heads but i'm using the one without the o.ring cutout as it would be too close to the bore - you can see the difference in chamber profile!) with standard gasket it gives a .6mm squish so far but will check in a bit when it's bolted up. that's with a 1.2mm base spacer & 2 base gaskets to get round the 1.4mm piston to pin difference. got to trim a new head gasket out to match the bore then put it together
nice project mate..i like the idea of tinkering with with a stroker if i ever get bored of fuckin with the r1 i might get one...are the principles the same for power gains?..porting and pollishing. raise compression..carbs and exhaust mods..whats a squish band?
m8 these things are a hoot to ride... and the bits are so fkin cheap it's untrue. like you can get a piston kit for £12, big bore kit incl barrel head, piston etc for £70 lol, absolutely nothing to them and so easy to tune with being a 2 stroke single. if you look on youtube theres guys taking these little engines to 30+bhp lol! get one!!! you will love it - and..... full tank in my storm / sp1 is about 20 - 24£ full tank in the ped, £4.20 lol and gets me nearly as far! £16 a year road tax... peanuts to insure... keep your eye open and you can pick up a seized one with good panels for a 1er. regarding the tuning side of things and the terminology etc, have a look in the downloads section at the 2 stroke tuning links.... particularly bell's 2 stroke performance tuning bible - it's everything you need to know - then theres some nice software for calculating optimum port dimensions & expansion chamber design. with your obvious engineering skills you could do really well on a 2t lol. ideal candidate would be a ape rs125 or other simple 2 stroke single. @elliot - ive still got the baotian m8 but a neighbour is after buying it for £250. not struck a deal on it yet like as it still needs a few jobs doing to make it more reliable. fkin fast ped that is, does 60+ on a good road! was a dodgy stator that caused the problems on last years beasty
anyway.... i used a short reach plug for now just to test it - kicked over no problem but the compression is well up from before! couldnt take it out on the road cos of all the ice so just gave it a good thrash in the garage.... front end comes right up & laid down a nice darkie on the garage floor lol cant wait to road test it! defo a good mod if you have a cast cylinder! :cheers:
bell,s 2 stroke tuning bible ...thats not the same corky bell that wrote the turbo tuning bible is it?
believe it or not its alexander graham bell. yes. i know. better known as A. graham bell so not to confuse the 2! gets a bit technical tbh & will probably bore you a bit. best thing to do is get familiar with the basics like port events & squish etc then have a play with the porting software on a simple engine. this is how they work -
its a good pic that cos it shows how the expansion chamber works.... as the hot gases expand it creates a pressure wave which stuffs the fresh mix back in the cylinder. on a badly designed exhaust, most of this charge is wasted which is why on a lot of peds and restricted bikes you can smell unburnt fuel behind them. the exhaust port is open at the same time as the transfer ports so if the pipe is badly made, or unsuited for your tune, it won't blow the mix back in so not only are you losing power but also get very low mpg & foul emissions
Haha awesome, you guys love peds too ! anything with a bloody engine i guess ? you might like my twin engined mini-mogo-ped project then iv got a scoot but its a 'reliable' 4T gilera runner (new shape) just wanted it to keep my mileage down in the car (limited for insurance) and also to save on some fuel ... cant wait to see yours going ... i just love the peds as you dont really have to do anything, i just sit back and pretend im on holiday haha
i read a good bit of the 2 stroke tuning link till it got to the port mapping bit and i got a bit confused and lost the will to live...still interesting tho. as with anything ..start with the basics and the rest will follow
Yeah i sctratched my head there to and thougt f*ck it thats why i get someone else to port my 2 stroke barrels :doh: :lmfao:
