Back pressure

[Kurtis100]

Is there anyway I can leave the end cap off my muffler on the 66cc and still have enough back pressure

 

[GoreWound]

by leaving the cap on? lol
is there a reason you want the cap off? if you just want your exhaust to have a big pipe opening you would do better butting a wide tip over it and leaving the cap in place (you might be able to get one from an automotive store that fits)

you can also get more back pressure by having more pipe length, that and a narrower pipe.

if you are worried about the muffler filling with oil you can try and get the end cap so the outlet is at the bottom, that should help let it out.

 

[frank66]

it will make the carb jetting incorrect likely the more u change it. the banana pipe without a silencer is ok but its missing 20" of pipe /so top end is worse than stock.

 

[2door]

Unless you live and ride in an unpopulated area maybe you should give more thought to the impact that loud exhaust will have on your neighbors and the hobby in general. The performance increase will be negligible but the annoyance factor will not do anyone any favors.
If you're looking for a better exhaust system and an increase in power you should look at some of the expansion chamber systems offered.
Removing the end cap is not the way to go for several reasons.

Tom