Does anyone thing that leaving the cleanout bolt removed from the bottom of a p-650 silencer will reduce back pressure? I removed mine and chiped out all the carbon, seems to be almost as much air coming out of that hole as the normal exhaust outlet.

 

Less exhaust backpressure is not always good. With less backpressure, you usually gain top end power but you may lose bottom and mid-range power. Which one do you want? Also, you can't make more power without adding more fuel to burn.

 

Leaving the bolt out can help start forest fires.

If you want to reduce back pressure, cut the muffler off.

Look up NYROC web site and he has a muffler mod that I used and it work great.

It involves removing the muffler, cutting of the end cap, cutting a little on inside, and drilling some holes. After the muffler mod, K&N air filter, Black rear spring, I could out run stock 650P and some that were modified with other exhaust and add on's.


Good luck...........handycap

 

Or just get an aftermarket exhaust. If you ride in sound sensitive areas make sure and get one with a quiet core insert. I'll stay away from the back pressure subject everyone has their opinion. But how many dragsters have you seen with new car exhaust, none. But on the flipside the fuel milage on a dragster sucks and they tend to be a little loud. Which in many parts of the country is the last thing atvs need to be, you know political correctness and all.

 

The sounds is marginally louder, you would not notice if you were not told. I do not anticapte a forest fire as I will be ridding in Montreal with a 3 foor base of snow, somewhat higher elevations and my jetting has already been increased per my profile. I want to add a little more air flow so as not to run rich on the trip. I already have the snorkle mod, Twin Air filter so I have better intake flow I just need more exhaust flow.

 

Personally I would still recomend an aftermarket exhaust. However if you don't want to spend the money than nyrocs mod will help to increase your exhaust flow. I don't know your altitude but if I remember correctly you are running the mains that were recomended by hmf for a slip on exhaust so your jetting should be in the ball park either way. I say go aftermarket because the exhaust will be far less restricted and with a quiet core it will not be much louder than stock. Plus if something should happen and you decide to sell your quad the stock exhaust is still avaliable and in good working order.