40mm minarelli cil

[street_sweepah]

hello guys, im wondering if i could tune my stock 40mm mina cylinder using the factory stock pipe and carburator. can you guys give me a port map or give me the exhaust port measurement without compromising its reliabilty and fuel consumption.
btw, im using a modified transmission. center and clutch springs are both 1500rpm (not heat treated, cause it is too stiff for a stock powerplant i guess)
i hope you guys can help me out with my silent cruiser project..
TIA

[tiba_karotsu]

do i hear stock mina cilinder? yes you can tune the stock cilinder to the max if the walls are thick enough, is it LC? the stock cilinder has lots of potential you just have to port it right. with stock carb & pipe port don't go overboard with port size, maximum port duration should be 180deg & keep the transfers below 130degrees.

if you can raise compression ratio without detonating then do it, we have been doing stock cilinder, pipe & carb tuning for a long time, for example i have a yamaha Jog SuperZR with an 88cc engine (replaced the 50cc engine with a 88cc engine, a direct swap & no mods), the carb is still stock (it came from the original 50cc engine) with original airbox & jetting still intact, the only mods are as follows;

high compression head (aircooled)
45mm stroker crank
CMR street pipe
Ueno vario kit (asian brand)
Malossi Kevlar belt
Chamelion factory torque driver
7,4:1 gear kit
malossi Yellow contra spring
MK red clutch springs

the cilinder is still untuned & i got 35km/1L gas consumption, topspeed with me is 115kmh & acceleration up to 90kmh is good, with 50cc your stock carb & pipe will work just fine.

[street_sweepah]

Originally Posted by tiba_karotsu

do i hear stock mina cilinder? yes you can tune the stock cilinder to the max if the walls are thick enough, is it LC? the stock cilinder has lots of potential you just have to port it right. with stock carb & pipe port don't go overboard with port size, maximum port duration should be 180deg & keep the transfers below 130degrees.

if you can raise compression ratio without detonating then do it, we have been doing stock cilinder, pipe & carb tuning for a long time, for example i have a yamaha Jog SuperZR with an 88cc engine (replaced the 50cc engine with a 88cc engine, a direct swap & no mods), the carb is still stock (it came from the original 50cc engine) with original airbox & jetting still intact, the only mods are as follows;

high compression head (aircooled)
45mm stroker crank
CMR street pipe
Ueno vario kit (asian brand)
Malossi Kevlar belt
Chamelion factory torque driver
7,4:1 gear kit
malossi Yellow contra spring
MK red clutch springs

the cilinder is still untuned & i got 35km/1L gas consumption, topspeed with me is 115kmh & acceleration up to 90kmh is good, with 50cc your stock carb & pipe will work just fine.

oh that's great.
btw, I'm using a racing crank.. 39.2mm.
I just wanna port the exhaust. should I raise it about 2mm or is it too big for a stock?

looks like we have the same specs but you are using a street pipe, long stroke crank and high compression head.

tia guys for your inputs

[tiba_karotsu]

Originally Posted by street_sweepah

oh that's great.
btw, I'm using a racing crank.. 39.2mm.
I just wanna port the exhaust. should I raise it about 2mm or is it too big for a stock?

looks like we have the same specs but you are using a street pipe, long stroke crank and high compression head.

tia guys for your inputs

just don't go over 180exhaust port duration it'll work with stock & street pipe with little or no changes to jetting if you maintain the stock airbox.