60mm crank and 1mm packer

[tavspeed]

hi chaps,got a standard cast 225 and running it with a 60mm crank and 1mm packer plate,saigon scooter taffspeed copy and 30mm dellorto,and 1mm removed from piston skirt,piston was level with bottom of transfers and exhaust port and level with top of barrell,
so a 1.5mm gasket was used to get a decent squish.
was really hard to start and jet in with the dellorto,after a couple of seizes stripped it and have a new piston on its way.
would i be better not using a 1mm packer,so the piston protrudes 1mm and then use a 2.5mm gasket for the squish,
just wondering what the 1mm packer and taking 1mm of the skirt has done to the port timings,cheers.

[rosscla]

You should be able to simulate that with one of the port calculators, just adjust the deck night for the same measurements and you should get the timings.

[rosscla]

Here

http://scooterotica.net/page19.htm

Just remember that 1mm out the top goes in as -1

Looks like dropping the barrel by 1mm would take 4 degrees off your exhaust timing on a 107 / 60, but plug your own figures in and see how it looks

[tavspeed]

ok will do and post back,cheers

[tavspeed]

right i have measured the ports and get these measurement and run on the port timing calculator

exhaust = 40.6mm 150.7 deg

trans = 46mm 126 deg

inlet = 93.5mm 149.65 deg

these are with a 60mm crank no base packer,piston protrudes 1mm to give a deck height of -1mm

intend to run with taffspeed copy ehaust ,30mm phbh,sx200 gearbox 16 tooth on front

the blow down doesnt look right to me 12.5 deg,whereas a standard cylinder is more like 18 deg according to mb's tech pages,any thoughts,cheers all

[B-Race Tuning]

You sure the exhaust is 40.6? would expect to be more around 30.6. ?????

[Yanker]

right i have measured the ports and get these measurement and run on the port timing calculator

exhaust = 40.6mm 150.7 deg

trans = 46mm 126 deg

inlet = 93.5mm 149.65 deg

these are with a 60mm crank no base packer,piston protrudes 1mm to give a deck height of -1mm

intend to run with taffspeed copy ehaust ,30mm phbh,sx200 gearbox 16 tooth on front

the blow down doesnt look right to me 12.5 deg,whereas a standard cylinder is more like 18 deg according to mb's tech pages,any thoughts,cheers all

Hi,

Curious as to the method theat you use to qualify port timings to within 0.1mm

Thanks

[tavspeed]

definetly 40.6,measured with digital vernier's. a 30.6mm exhaust would give 190 deg of duration,have a sandard 200 barrel,i will compare the ports,wonder if i have a lambro barrell as it was bought at a parts fair,
have calculated my blowdown as 25deg,which is then halved to 12.5 deg,is this correct
and is this a usable barrell,cheers all

[drunkmunkey6969]

No....it's not useable. Lol.

It'll run, but it's not useable.

I'd be wanting 170+ degrees MINIMUM from the exhaust port.

[tavspeed]

Measured a 200 barrell and exhaust port is approx 38mm should i raise the exhaust port 3.5mm would this work