Topic: MAC 4-2 Exhaust Fitting on stock CB500 Headers

[farinhite]

Hi!

I have a 72' CB500/F in which I'm trying to fit a MAC 4-2 slip on muffler system on the stock headers. The headers seem to be cut right before the stock muffler is to start.

Because of the angle of the stock 4-4 mufflers on the 500F, the ends of the headers have a slight up slope to them.

That being said, the MAC 4-2 mufflers slip well over the stock headers, except the angle is completely wrong, and they dont even come close to the mounting bracket on the bike. I'm thinking that the headers might just need to be cut down, however I'm a weary of trying this without knowing exactly what point in the headers I should actually cut.

Has anyone fit the MAC 4-2s over the stock headers? Looking for some advice on where to cut them, or if it's even possible to fit the MAC system without bending the headers into shape.

Thanks!

[That 70s Bike]

I'd think you could find the MAC instructions telling you where to cut the pipes.
These were already cut for unknown slip-ons but they worked on vintage slip-ons I had.

You are correct, the headpipe end needs to be cut before it curved up to the old muffler. The end of the headpipe needs to be straight to slide in, & the longer the better since it could leak & soot-up there.
I have seen instructions that use the footpeg bolt as a reference point.You could hang one muffler & note where the 2 slip-ons end. Then hang the 2 pipes on that side & make sure your cut will be as long as possible on the straight part that goes into the new muffler pipes.
These replacement muffler types are designed to be a simple install onto cut headpipes without any complications like bending anything.

[farinhite]

Thank You so much!

I called MAC and their only advice was to cut once inch at a time until they fit.

This is actually the first picture and diagram of the Mufflers I've seen actually mounted so far.  They've said that there should be at least 3 inches of overlap between the headers and muffler in order to keep avoid leakage.

This will at least give me a good reference of where to cut the pipes.

BTW your headers are super clean. Did you have those re-chromed? I'd love mine to look that nice. After sanding and polishing off the years of rust, mine are looking pretty dull.

[Rigid]

Any muffler shop can cut and form an adapter pipe to get the angle and length you need.  If placed inside both pipes it is not even seen. 

[orange550]

Sort of related, but other than the Mac 4-2, does anyone know of a new 4-2 for these bikes, that uses the original headers? Or maybe a great 2-1 collector so you could use some other muffle tips?

[That 70s Bike]

Thank You so much!

I called MAC and their only advice was to cut once inch at a time until they fit.

This is actually the first picture and diagram of the Mufflers I've seen actually mounted so far.  They've said that there should be at least 3 inches of overlap between the headers and muffler in order to keep avoid leakage.

This will at least give me a good reference of where to cut the pipes.

BTW your headers are super clean. Did you have those re-chromed? I'd love mine to look that nice. After sanding and polishing off the years of rust, mine are looking pretty dull.

They should be able to supply you with an installation sheet if you give them the model info of their muffler (assuming the model is still sold)
Re-chromed? No, just my favorite: Turtle Wax Chrome Polish & Rust Remover- $2 at Walmart...before>

[farinhite]

Now thats some elbow grease!