If I remember correctly, the last one I had used a different bolt pattern on the cylinder than the water cooled version. I only had one of the "VA" type listeroids. My impression was that it was much colder natured than the water cooled engines. BTW, the "VA" type air cooled Listeroid is still legal to import until 2009 under Tier 1. Tier 1 places compliance on the user/operator. I ran emissions tests and it easily cleared Tier 1, and especially since the "in use" limits are 125% of the test standards. The air cooled engine is a nice one but tends to be a bit noisier than the water cooled variety.