thinner base gasket
 

will a thinner base gasket effect jetting at all??? i just installed a new piston/ rings/ thinner base gasket and after a quick 1st ride (15min, 5km) i looked at the plug and it seamed abit leaner than the plug i took out before the rebuild or is it just because it has only been ridden 5km??

It will change your port timing....

and compression.

I just did my first top end too. My bike had a .3mm and .5mm from the factory. I put in the .3mm and .15mm and I was amazed at how well the bike ran when I fired it up. My bike always ran well, but never as crisp and clean as it does now.:)

i found that after going to the .3 by its self it got some bottom but lost some topend it will only do 134kph now, were even before i rebuit it it was pulling 143kph(ish) like it did from new i did use a wossner piston that is slightly heavier that vertex?? that i took out. i also think it is a little rich on the pilot now

Did you measure squish or compression before/after? If not, it may be difficult to tell exactly what is going on.

It may be more than the base gasket. When I rebuilt my '06 EC300 the crown of the replacement piston measured 0.23 mm higher than the original piston.