its nice to hear u got it running good. you'll probably have to go up a lil bit on the main again once u get the R4, but try riding the bike with the 155 main before u re-jet for the R4. that way u'll get an idea on how much more u need to go up on the main, if ne at all.

 

the 155 dynojet is actually too big. it should run much better than with the 165 in though. a stock keihin 148 mainjet is equivalent to a 142 DJ if i remember correctly. so around a 148 DJ should be more than enough, but the 155 would work if you don't have anything else. yes, going with the smaller mainjet will increase your top end.

 

i didn't realize that dynojet uses a dif. sizing system, i figured the only difference would be in the design of the stamp on the jet. don't got too small on the main, it may increase top speed but if u start running lean (your headpipe will get really hot all the time) you can really mess stuff up.

 

yes, the sizing of the mainjets are different, which can change things around. you don't want to go too small or you will be running hot and can cause engine damage. i run a keihin 158 in my 426.