2003 Yamaha Zuma from trash to 100cc3 beast

[tysta]

Hi 
in this post i will share the my build were i started till where iam at this moment.

Initially i was thinking in build this zuma just to have a a nice functional scooter as pitbike or to go around if needed when at the track
this is exactly how she started

  


but soon i got it home my mind went right to humm how about a high revving 70 engine would be nice like 15k

so i start to order some parts went right away with a S6 mk2 cylinder 10mm pin to reduce weight their special crankshaft made for high revving engines at the time i think i purchase the very last one in stock lol






and from this point on i never stopped always looking for something else to do on it
just because i was not happy with the performace
from high revving i went ahead and got a 12mm pin piston a new crankshaft ported the cylinder more
modify the engine cases and i started to realize i needed a much better intake and a better carb so from a 22mm pwk i went to a 28 mm carb with the carb facing backwards , a new subframe was also installed. at this point i had all new plastics and fairings for it.










also the first cvt setup was not the must suitable for my setup so i decided to go with a full S6 cvt kit

as iam going more and more modifications were being made i think this a very resumed description of my battles not every thing was roses , being a tech for over 25 years and dealing with race bikes and everything in between didn't prep me enough hahaha
whe you are trying to squeeze all the juice out of one of these    

[tysta]

always finding the small things to try to improve best i could 

from carb modifications intake reeds i didnt spare any time and try to cover everything  



new brake caliper with a big rotor and a dry brake line connection.
the rotor is so big the only way to remove the wheel is to lose the rotor to remove the caliper good luck doing that with the wheel in place. so whit the dry connection the caliper can come out with the wheel much easier.

after all this the scoot is doing about 78 mph but i didnt had that kick i love from all my strokes so this wa the turning point
i decided to go liquid cooled and going from some serious power for a scoot

but the big dilema was what route
 or i would go like a rc one cases or something similar but there's a problem 
i love the look of the stock wheels since i didnt find a solution at the time i decided to use the stock cases to keep the rear wheel stock
now time to chose witch kit and after talking with a few friends from the mother land i chose the 2 fast 100cc3 

















and as expected nothing remained stock hahaha

starting with the cylinder i checked the port mapping and made some changes to tailor the engine characteristics.

  

i will post some photos of the cylinder after work done need to find the for some reason i cant find them right now

to fit this kit on the stock cases its a bit of a nightmare since the crankshaft webs are gigantic compared with the stock one
the cases need to be milled but soon you mill the cases the sealing surface is gone now you need to face the cases and gain some sealing surface back but to compensate that you need to ad a spacer. the spacer sold by 2fast does not fit our cases since they are made in Taiwan by Yamaha and not by minarelli they are not quite de same so i also ad to make my own spacer.
at this time i didnt had a milling machine or cnc not eve access to one i only had a small lathe and a drill press 
got around using a cheap 2 axis vise and doing the milling on my drill press i must say i got luck getting away doing all that work like that

[tysta]

here some photos of port work






most the times after i share photos of my cylinders i always have someone asking and the answer is yes i can port/modify cylinders  cases for you guys .










after some time i was able to make some tools and figure out the best way to do the job and start testing some parts

[190mech]

Nice Work!!!

[tysta]

Nov 30, 2023 4:58:15 GMT -5 190mech said:

Nice Work!!!

Thank you!

[tysta]

as obvious this does not end here lets call it 1st stage
soon i got it running with the stage6 cvt setup (old setup from the air cooled build) i couldn't find a proper working setup
and she felt very weak meaning not putting the power out and after a long fight i decided to my torque drive and variator .
couple of my friends back home who still race scoots the kept mentioning 2 possible setups for the cvt combo.
so i order a torque drive (furia rossa) a new belt from polini and the variator i decided to use one i actually bought by mistake its a polini speed variator made for some oversize crankshafts
and for my surprise right on the first test the scoot was completely different like night and day different now we talking

but problems start to happen

belt alignment ,spacing between clutch bell and clutch , spacing between clutch and the torque drive when fully open

the torque drive comes with a small flaw the grove for the retention c clip of the bearing is not on the right place leaving room for the bearing walk that means when the engine running the torque drive  can walk in and out and in some setups like mine the if it walks all the way in the big nut on the torque drive will touch the clutch bell solution is to install a shim between the c clip and the bearing. to my knowledge all furia rossa are like that this problem will not reveal in all setups same thing with the primary gears the imput shat walks a decent amount too. not all of them depends on the  brand/model. 

 
yes its a 35mm carb 
the fight is long trying to cover every single details on the cvt i even got to the point of getting some secondary gears for the European engines and use one oem gear cut the center and make it work for the output shaft and have a ratio cable of reaching speeds over 100mph is the engine have enough power to pull
no need to go that fast but i always felt something wasn't right till i realize the scoot was destroying any reed valve i would install

this was a nightmare
on my Vforce reeds i try everything all kinds of reeds different thickness they will fail after a short ride with 2 or 3 pulls

to the point it actually broke the reed cage   


 



at this point i came with the ideia of making a reed cage but because i still didn't have a cnc i decided to use something already in the market and make my own from that

 



ate least i knew the cage wont be able to brake it   at this point only one the reeds keeps failing even after all my efforts
after losing some hours of sleep over this and talking with other 2t gurus friends of mine we came up with one possible cause
the pressure wave caused by the piston on is descendent movement is so great affecting the top reed only exactly same direction were the spacer and the cases meet . i did move the reeds even more back and at this point i can say i could ride without problems but i know it will fail at some point since the engine revs so high.







a little video of if running
youtu.be/CkJ3YcWAXTw

  






yes sometimes i make my own tools too hehe