my 2t ped...

[mattster]

Interesting read Benny, although it's all a bit too technical for me!!

I do agree with you on the ring flutter though. My butt would be fluttering like hell at 80mph on a ped too!!

[AMCQ46]

it sounds like this ped will go like a rocket!






lots of noise, smoke and flames, an impressive burst of speed, then it will explode

[benny hedges]

negative bugger lol, where's your sense of fun!!!

[AMCQ46]

you cant beat an aircooled 2 stroke for engineering fun.

I converted my MZ race bike from piston porting to reed valve, fitted a MX piston that was designed for reed induction but that was 10mm shorter pin to crown, so had to take 10mm off bottom of barrel. Welded up extra metal on the crankcase and bottom of the barrel so I could then cut in bigger transfers and a 5th port at the back.
Tip when welding an aircoled barrel is to put it in a bucket of sand, otherwise the heat dissipates too fast because of the big fin area.

topped it off by reprofiling the combustion chamber to match the angle of new piston crown, get the squish area and clearance correct, then made my own total loss electronic ignition system to replace the points, bored out the carb to an oval profile [rules stated we had to use stock carb], bored out the emulsion tube as it was still lean with no main jet fitted, then had to make my own needle to run in the bigger tube, then cut and welded the cones and stinger for 3 or 4 options on expansion pipe.

Then went out and won races on it ..........still the lap record hoder at 3 sisters for that class [but they did stop racing there just after I stopped]

[benny hedges]

yeh i love em
you can do anything and either win or fail.... either is cheap!!
when i raced them i soon learned that going onto twins (x7s) costs twice as much lol!
thats the beauty of peds... everything costs peanuts!

[benny hedges]

wtf lol!! i just put it back together with the 70 piston, porting mods, crankcases matched, squish set to .8mm and proper plug...
sounds like a racing chainsaw lol! vicious little bike lol
ill add a vid tomorrow ---
justsmoked the street out revving it, popped a wheelie o the drive, then noticed someone is viewing the house next door lol oops sorry!!!

[benny hedges]

nipped to see a mate tonight & came back with a set of minarelli vertical a/c cases, variator casing with cnc cut vents, gearbox assy, loads of shafts, spare crank, cables, calipers 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!

[tony.mon]

Jetting will be a pain, I think.

[benny hedges]

yes. i agree. but i have my trusty 30 year old gunson colortune ready
ive hit a snag with the carb though, the bigger one... the bowl is too deep to fit so i may have to turn the reed block 90* and mount it sideways :/

[benny hedges]

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!

[lloydie]

thats going to be one mental ped

[AMCQ46]

Last a bit longer .......measured in what units?? Milliseconds?

[benny hedges]

been busy, seeing as im iced in!

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

[benny hedges]

fek! bastid spark plug hits the piston! bollox!

wheres me copper washers

[agentpineapple]

what are you trying to achieve benny, more speed plus reliability?
you gotta get it to itely and back haven't you, and what sort of top speed do you think you can get?