[doug80638]

Mea cupla! No offense was intended.

The problem with "loud pipes saves lives" is that no one ever says  when loud is loud enough. Noise and spark arrestors are certainly not an issue on the track.

Cheers.

[thunder1]

I can tell you from experience that if you remove the spark arrester and end completely it will reduce the back pressure enough that it will run too lean. See my writeup in the How Tos. When I just put the 2" tip on it with nothing else it was so lean it lost power, ran hot and the plugs were pure white. When I added back in the HMF spark arrester screen, it took it back into its range but just barely. It's still close.. on the lean-side but that's OK for this altitude. If I had to go any lower then 5000 feet I would have to put my OE end back on.

Just a wild guess but was it the motor with carburator and without fuel injection? I guess that with fuel injection motors the air and running lean problem should not be an issue?

I am asking because I am thinking adding larger exhaust tip and I've heard some rumours that bigger exhaust tip can also help to keep exhaust cooler as a bonus added to the motor working better.

[NMKawierider]

I can tell you from experience that if you remove the spark arrester and end completely it will reduce the back pressure enough that it will run too lean. See my writeup in the How Tos. When I just put the 2" tip on it with nothing else it was so lean it lost power, ran hot and the plugs were pure white. When I added back in the HMF spark arrester screen, it took it back into its range but just barely. It's still close.. on the lean-side but that's OK for this altitude. If I had to go any lower then 5000 feet I would have to put my OE end back on.

Just a wild guess but was it the motor with carburator and without fuel injection? I guess that with fuel injection motors the air and running lean problem should not be an issue?

I am asking because I am thinking adding larger exhaust tip and I've heard some rumours that bigger exhaust tip can also help to keep exhaust cooler as a bonus added to the motor working better.

No. The 2015 was EFI. There is only a small range of correction EFI can take care of and dropping more then half the back pressure took it outside it's range. I had to put back in a HMF spark arrester to get it to the far end and it was still very lean and doggy on the bottom end. I have sense cut the end of the old arrester and end and sandwiched it in with the new 2" pipe so I can still run my silencer May not have the top end power it had but it got back all the low end stuff it lost...and that where I run any way so..it was good...and it's a little quieter.