Topic: Modified MAC madness! Need advice...

[BARKER]

Hey guys,

I've got a rough old Mac 4 into 1 that I want to use on my 74' 750 project. I basically want to shorten it up a bunch (it's damaged in a few areas and the original muffler is M.I.A.).

I'd like to have a silencer or baffle to help tame it down a bit though. Any thoughts on how I could do this? I was considering making my own but I'm not an exhaust system scientist/engineer/brainy bike dude. I'm wondering what the ideal diameter of  the silencer should be? I have a silencer from another project but I'm concerned that it might be too small and really suck the life out of the bike.

The attached picture shows the length I'm thinking of cutting it down to.

Thoughts?

[Killer Canary]

Hello,
the physical size of the silencer isn't as crucial as the amount of constriction built into it.
If it's a chambered silencer it will have restriction built in; if it's a straight through baffle it'll have little restriction.
If you're handy with fabrication tools a reasonably efficient multi-chambered baffle can be made quite easily for an existing silencer.

[BARKER]

Yeah the constriction is exactly what I think I need some info on. I don't want to choke the bike, but I don't want it to shake the neighbors house (much) either.

[Stev-o]

Have you seen these?


https://www.ebay.com/itm/MAC-Performance-Kerker-Style-4-1-Competition-Reverse-Cone-Baffle-009-1119/161772357838?hash=item25aa6248ce:g:WfIAAOSwErFZ2Auz&vxp=mtr

[dave500]

I made a straight through baffle for a megaphone,the end cap is a vee pulley with the vee cut off and a short sleeve welded on to go over the perforated tube I bought,its wrapped in glass wool and held in with a bed spring,the Yoshi plate riveted on makes it go faster!you could use a straight piece of exhaust tube as the main body?

[dave500]

the end cap actually reduces the outlet with a "genuine"yoshi part with the Honda applicable middle number on it!

[sixthwisconsin]

Dave,
Are those blood stains on your work bench? I have those too!!!
Yoshi is worth 5 hp easy.

I ran the performance MAC restrictor for awhile and really liked it.

[dave500]

yeah mate had a mac with reverse flow baffle,sounded like pinching you nose together and humming an engine noise,we removed the stupid offset baffle affair and drilled the solid tube with one million holes,welded it back together in a straight line and wrapped with glass wool,sounded much better but not overly loud,mate reckons it ran slightly better mid range pull.

[sixthwisconsin]

I also drilled my performance baffle for better sound. Don't remember how many holes I drilled though. I ended up replacing the MAC system with an original F header with a CONE muffler.

EDIT:
It was the OEM baffle that I drilled, not the performance that I ran in it last before selling it.

[BARKER]

Thanks for the replies fellas.

I'll post a pic of the part that I'm thinking about "making work."