Hi, I've a Suzuki Quadsport Z400 (2004 model) and I'm jetting it. I bought a full exhaust system (CT Racing), a K&N filter with Outwears, a Dynojet kit and a #25 pilot jet. I removed the lid, installed the pipe and the filter with Outerwears, and tried the #160 main jet, 3rd clip on the needle, 25 pilot, and 2.5 turns out on the fuel screw. It run fine, better than stock. Then I tried the #155 (everything else equals) and it run better, more top end. Next I tried the #150 (the recomendation from Dynojet instructions) and it run better than the 155. I live in Spain at 1500 feet and a temperature from 50 in winter to 90 in summer. The point is that all the people I know from z400central or thumpertalk with the same configuration as me (full pipe and no lid) use bigger main jets, even with higher altitudes. I think a #150 main jet will be lean, but is the configuration that has a higher performance. The question is, is the 150 safe or maybe i'd have to choose the 155 main jet? On the other hand, I don't ride at full throtle all the time (I use the quad for trails, not mx). Thanks in advance!