wtf do those so called performance exhaust inserts really work?
they claim to get a power gain cuz your going from a 15/16 inch exit to a 2 inch insert but i think it sounds like a little b.s cuz your still using your stock exahust and all youve done is put a bigger tip on

 

If you modifi the exhaust you'll most likly need to rejet the carb , i don't think you'll gain much power with just an aftermarket exhaust and carb rejeting ; most people who mod their quads add a K&N air filter and a few other things in order to see much power increase !.........

 

Just the muffler on a 400ex won't make much difference......

A muffler or slip-on will add is a little low end on an engine that is mid-range and top-end strong engine like that of a z400.... the z400 is a DOHC engine and has a VERY stuffy muffler on it stock, and it mill makes very little low end grunt. So a slip-on will make some low end difference.

The 400ex and most push-rod engines already make a ton of torque down low, so getting any more is not really possible with just a slip-on...... for any real gain you will need to do the head-pipe and muffler, along with a jetting upgrade.......

You won't NEED to rejet with just a muffler, but you won't see any real increase either. All you will be doing is making it louder.

 

i was just reading up on exhaust upgrades and stumbled on that and didnt think it would help my cause any i figured i had a good low end but im lookin for more mid and top