My friend has a V-FORCE and he put a K&N filter on it last week. We ride at sea level, do you think he should go up a jet size. My first guess is no. I am sure they are set up a little on the safe side from the factory, so the little extra air should not hurt anything in my opinion. I do not have any experience with the V-FORCE and jetting so I do not know for sure. I ride a piped raptor. What do you V-FORCE guys think? Should he rejet? We rode it after he installed the filter all day, and it ran fine, we have not looked at the plug though. Thanks.

 

I would go and get a 143 jet. Put it in the back and move the 140 from the back to front. You are correct to say you won't "hurt " anything but more air begets more fuel. It will run a bit better. I ride at 2700-3000 feet and it seemed to runfine with factory jets. It ran better after I tried a few different sizes. Check your plugs, go for a rip, change the jetting and immediatley go for another rip. check the plugs after 10 or so miles. Do they look better/worse, did the machine performe better / worse. It is all trial and error