My z4's engine has been stock for 2 years now. Decided to play today and ordered a complete yoshi exhaust system and a moose jet kit with a uni filter.Would love some input on what jet to startwith. I have raced gokarts in pro classes for a long time and do have some knowhow on reading plugs just would like a good starting point to get me close. The day after i get it on, im going on and all day ride and dont want to damage the motor(altho it would be a good excuse to get my wife to OK a bigbore kit ha ha)

Also, have read you guys talkin about the z4 bike head gasket being thinner than the quad z4. Had my dealer look it up and he said it was the same part number therefor the same part???? Would love the extra compression. Whats the deal?

 

The bike you need to get the number from is the DRZe. The stock gasket on the quad is a 3-piece gasket, the stock gasket for the bike is a 1 piece gasket. The bike gasket is the same size as the center one one the quad. Some people use the center gasket off the quad gasket. It bumps the comp. up from ~11:1 to ~12:1.

As far as jetting a 160 mikuni main is what I used when I had a K&N w/o lid and pipe. FYI, Mikuni and dynojet sizes are not the same.
I also bumped the pilot up to a 25. elevation ~600ft above sea level.