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Hi all,

I don't want to make any outrageous claims (that's another thread, and perhaps another site ) but am curious if the factory cam HP of 385 is based on standard air filter and muffled pipes. I have a K&N filter, rejetted Holley 750 and open 2.5" pipe set-up - would this provide any more HP over the stock restricted set-up If so, any idea of an amount?

Just curious

GordonBH wrote:Hi all,

I don't want to make any outrageous claims (that's another thread, and perhaps another site ) but am curious if the factory cam HP of 385 is based on standard air filter and muffled pipes. I have a K&N filter, rejetted Holley 750 and open 2.5" pipe set-up - would this provide any more HP over the stock restricted set-up If so, any idea of an amount?

Just curious

A better question is does it even matter? lol I am sure someone will have a real theory on straight pipes versus some sort of mufflers.

My experience is with a Big Brute Motorcycle...first V8 I ever had. It came with some really nice slip on mufflers that gave it a great performance sound without being too restrictive. We had a huge event in our big city and I thought it would be cool to run straight pipes so off came the mufflers. it made so much friggin noise and it seemed to just make noise and not have the getup and go from a light that it had before. As soon as the mufflers went back on it went like a raped ape again. Was it just my mind or did it actually run worse with the straight pipes??

Interesting stuff Barry, my recent experience taking the bike to the tough UK test (with quiet and restrictive mufflers) was that it was a touch more mild-mannered but then I had to lean it out for that run - and the roads were wet.

I definitely prefer the sound of my opens and will run them until I get stopped but I've managed with open shotgun pipes on my harley for years over here. I just play quietly in towns - that rumbling burble says it all - people can hear there's serious power there. My main issue with them is the fast idle on start up - Wow that's not neighbour-friendly and I live in a cul-de-sac of old fogies. I am designing sound-reducing boxes to slip over the turn-outs until I can settle it down to a nice idle.

I have toyed with the idea of vortex cones but can't find them in 2.5"

I suspect the figures are from a pull on an engine dyno, rather than a chassis dyno. The engine was, most likely, run with no air cleaner and open exhaust.
Your results may vary, but I think the 385 figure is pretty accurate.

I only put the baffles back in at mot time....

Yeh Steve,
I'm toying with the idea of stainless steel perforated sheet rolled into a cone - like home-made Dynatex Vortex Cones, I'll use the same MOT guy that I used for my Harley which had two simple "snuff or not" 'baffles' I made with 1 3/4" dia. washers welded onto a bolt that I ran through a hole in the underside of the pipe - turn sideways for noise and face on to quieten. Worked fine for the MOT test and last year left them on "quiet" and they are fine as long as you don't crack open the throttle in town.