got an 06 rancher 4x4 manual shift,with 26" mudbugs-used for mainly trail with some mud,just wondering what the best size jet is to use and if there is a combo jet/exhaust that is good,,,,also will changing the jet have an adverse effect on reliability-i would rather make it out of the woods than have a little more power,thanks in advance

 

Not sure if this is answering your question, but the best way to fine tune, in my opinion, is to adjust the jetting by looking at the condition of the spark plug and listening to the engine while doing some acceleration/deceleration runs. If you are all stock now, what does your spark plug look like? If it's clean or light tan, leave it alone. If you free up the intake or exhaust with mods, you will need to jet it richer. Most of the time you can just bump up the main jet a few sizes to richen the upper end of the throttle opening. Some jet kits also change the needle or let you adjust the needle position by moving the c-clip up or down to tune the lower to mid throttle opening mixture. The pilot jet and mixture screw adjust the mixture at idle to about 1/4 throttle. I hope this helps you. A lot of people have different views on jetting. You can do a search and read for yourself. As long as you don't run too lean of a mixture, you won't hurt reliability. If you are worried most about reliability, just leave her alone. I like to follow this diagram from Carb Parts...

Carb Parts Jetting Diagram

 

Your post is a little confusing, because it sounds like you are asking if JUST rejeting will help anything??? Unless you have made some mods, no it probably won't. But, Honda does tend to jet a little lean to meet emissions standards, so fattening the jetting up a little might not hurt.

I am running an FMF MegaMax II muffler, a UNI air filter, and a lightly vented airbox lid.

You asked about jeting and reliability. If you make the mistake of jetting to LEAN, your motor will run hot and could definitely get damaged.