2.02 or 2.05 that is the question

Pick the smallest valve and port that will provide the adequate flow for the HP and RPM level you desire.

CFM flow without velocity is as bad as velocity without flow.

Given the limitations of a stock J Head in port volume, even ported the port won't flow enough air to support a 2.05 valve. The second issue is valve shrouding you didn't say what your bore is, but unless it is quite a bit larger than stock you can have a problem with valve being shrouded by the cylinder wall. For theses reasons I think sticking with 2.02 would be your best bet, at least until you can step up to a more race oriented head like a W series that has the port that can support the larger valve.

Regards,

Joe Dokes