pug speedfight & my other one...

[vvtr]

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

[190mech]

Why not make a cylinder spacer,that'll take care of the piston height problem and add some crankcase volume too.. :thumb:

[vvtr]

yup. great minds

i made a stencil but for the durations i want i only need a 1.25mm spacer with a standard gasket either side, then was planning to take 1mm off the top of the cyl, but looking at the crown on the new piston, i think i'll leave the skimming and jack it further if i need to as i will also probably need to lower the compression a bit.
i need to finish off the port mods before i get the rebore done, just in case i scuff the cylinder, then i'll measure up again for the spacer, with the new piston in place.
the main thing was getting the piston crown to gudgeon pin distance right... this is about 2mm off but should work ok.
it did last time anyway!
turned a bland engine into a Very sporty motor lol!

[vvtr]

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

[190mech]

I use the Mitaka catalog to compare piston and rod dimensions when I'm doing "off the beaten path" mods;
www.mitaka.co.uk/catalogue_index.htm
What about the ring locating pins?Are the rings going to snag a port??

[vvtr]

no, they line up perfectly the same as the polini ones, between the transfer & boost ports.
the last time i did thes the pegs were in the wrong place so i had to file them flat and drill another pair.... obviously a concern about them falling out and causing damage, or leaving a hole under the ring.

cheers for that link btw - bookmarked

[vvtr]

finished modding the new piston & cleaned up the crankcases...
put it all back together with the 70 kit with the new porting mods, correct plug & increased compression - what can i say

it's VICIOUS!

revved it a bit on the drive to clear the assembly oil, omg it sounds like a motocross bike!!!
soon as the smoke ceared i gave it a good fistfull with the front brake on and it wheelied from standstill lol, nearly dropped the bitch!

just took it for a quick spin round the block (havent put the cooling ducting on yet so didnt go far) YESS much better.
took off from a junction, straight to 45, overtook a few cars... this is how scooters should ride lol!
cant wait to get the 51mm bore done.

what ive decided to do is, as this 70 kit is so good, with new piston & rings etc, it seems a shame to bore it out so i;m going to keep this one as is for the time being and i'm collecting a scrap 70 barrel off a mate in a bit (the guy with the bobber!)

i'll port that to the same dimensions as the 70 kit im using atm nd then bore it out another 4mm,
watch this space - should be awesome

[90GTVert]

Sweet. Good idea leaving this alone for now. Our 2Ts wear out fast enough, might as well get your use from it before going farther.

[vvtr]

no m8 its just this 70 kit im leaving as it's sweet enough as it is plus its on a fresh piston & rings...
well happy with the porting on it

im nipping out in a min to pick up another polini 70 kit thats been seized and is badly scored.
plan is to port that the same as the one im using now and then bore that one to take the gt185 piston
cant wait to try it!

not that bothered about how long it lasts as ive more or less got another motor built up ready for spare... this is just a toy tbh, not like i need it for commuting, its just to harrass cagers on

[90GTVert]

Jan 14, 2012 13:18:23 GMT -5 vvtr said:

its just to harrass cagers on

:lol2:

[vvtr]

lolz well, you know how much fun it is pulling up at the lights, watching them scowl at you then they try to be cool as you leave them for dead in a cloud of smoke & noise lol!
Love it

good night tonight - went to see a mate, worked round some design issues with his pug / piaggio bobber.... it's now got a piaggio front end & will be getting a malagutti 80 engine this week & some gusseting to strengthen the frame and a battery / leccy box.
still got issues with the seat & where to mount the footpegs cos he's a big lad lol!

anyway.... the mission was to collect some spares so i 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!

[vvtr]

it is done.



86.48cc
decided to leave the taiwanese piston and instead went for a 53mm mitaka 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!

[90GTVert]

:thumb: :popcorn:

[190mech]

Looks GREAT!Handle that cylinder carefully!! ;D

[2strokd]

Congrats on that :clap: :wtg: ;D Great thinking for a cheap biggun :cheers:
Hope she stay tight.... But if not. Who cares, not much into to begin with right :nana: