I have a 05 rancher es with mud lites on itp c-series wheels. i would like to upgrade the exhaust, can i do that without rejetting the carb or does a new exhaust require internal mods as well. also who manufactures a good exhaust. thanks

 

You will need to rejet. The whole point is to free up the amount of air going through the engine, and when you do that you have to add more fuel to keep the mixture correct. If you didn't have to rejet, you have accomplished nothing except to waste your money! If you don't rejet, you will run lean and toast your engine.

I run an FMF MegaMaxII, but would go with the FMF Powerline if I was to get a new pipe today. https://www.fmfracing.com/products/c...CategoryID=130

Also, at the same time get a more freeflowing air filter. I run the dual stage UNI's.

 

i dont think you need to rejet if you get a hmf utility series.

 

You don't need to rejet unless you do a free flow exhaust AND free flow intake (air filter). A muffler alone will not flow enough extra to rejet unless you provide an avenue for more air to enter the engine.

 

Go ahead and buy a new exhaust and install it without rejetting. You'll be backfiring and bogging all through the powerband. You must rejet when you make any changes to the airflow of the bike. A freer flowing exhaust will draw more air/fuel through the head and you need to increase the fuel to keep your mixture right.

 

EXHAUST LESSON 101

Lets get back to the basic on how an engine performs with intake and exhaust flow. The quote above is correct.

You can take the exhaust completely off and the engine will still perform just the same. Granted the engine might pop on deceleration due to less back pressure but power will still be the same. The spent exhaust gases leave the combustion chamber through the exhast valves and once the chamaber is cleared and closed it does not matter how it leaves the exhaust unless there is a restriction in the exhaust system thus causing low flow of exhast. HOWEVER!!! If the incoming air flow is increased then it is recommended that a higher flowing exhast system is installed to allow the incresed pressures to exit the exhaust faster thus allowing the engine to breath better.

Think of blowing through a straw.....is you slowly close off the end of the straw then you creat a restriction thus causing more pressure to build within it. Therefore more effort is needed to flow the same amount of air...thus causing the engine to bog down.

Hope this helps out!!!!!

Ride hard and get muddy
CrazyJames

 

Nice post. Well put, thank you.