I did the NYROC mod to my p650 exhaust, I drilled 6 3/8" holes through all 4 baffles(12 inch bit), but I did not touch the spark arrestor or end cap. It has a slightly different tone but not real noticeable. How much more noise will you get if you modify the spark arrestor?

 

depends on what u do to the arrester if u get ride of it complety itll be like a harley. If u put a couple holes in it not too bad but will sound good.

 

I found it to be more "boomy" when you pull out the 1" tip. It's not bad when playing around, but at constant speed on a trail, I find it starts to wear on you.

But..... It's no louder this way that my buddies stock 660 Grizzley.

What I did was take a 2" hole saw, and drill out the spark arrester tip. I had this welded into a a piece of 2" thin wall pipe. Now I can slide the tip in, secure with a couple of screws, and it's quiet. If I want it loud (and the extra power), I pull out the 2 screws, and she's loud.

I like it that way. Now I have options! [img]i/expressions/face-icon-small-smile.gif[/img]

 

i have a modified end piece , a aluminum end cap that is siliconed and bolted in. it has a 1 5/8"hole. someone mentioned shotgun one time, well you don't want to ride on a sleigh being towed by my quad. my son told me once when he was camping at a lake not far from here and i was running on a road over a mile from him ,he could hear it and he could tell it was me , a very loud and mean snap to it, after all when you got that much power you might as well sound like it too.

 

Just wondering how much of a power increase in the bottom end and midrange with the mod done. Thanks

 

Well I did the mod, re-jetted, modified the snorkle all at the same time. It feels a little more responsive on take-off, but I haven't gotten to go on any extended rides yet.

 

I can now wheelie from a dead stop without pulling on the bars. Before I had to be moving 3 - 4 mph.
I lost a little on the top end but haven't re-jetted yet. I did have to adjust the idle mixture also. Overall well worth it. Before the mod the loudest thing on the bike was the tranny...... well not anymore.[img]i/expressions/face-icon-small-happy.gif[/img]

 

Has anybody drilled holes on the end cap around the spark arrestor. Then you could make a plate that bolts onto the end cap around the outlet using sheet metal type screws. Would that be approved by forestry inspectors. Or you could weld nuts onto the end around the holes, and then put short bolts in them when you wanted to be quiet.

 

That might be something worth looking into! I wonder out much this would change the fuel mixture? Ya know you wouldn't want to have to re-jet everytime you pulled the bolts out.

 

I'd jet for them out, and let it run a little rich when they're in. You lose less HP being a little rich than a little lean (and being lean runs the risk of detonation).