Topic: Mac Mufflers piss me off....

[Geeto67]

Ok, so I bought one of those Mac replacement mufflers that are supposed to attach to your stock head pipe on a 1978 CB750F. Well, the damn thing doesn't fit. The slip portion fits but over the stock header and the mounting flange doesn't line up.

anybody have any expirence with these? maybe I am just not doing it right.

[jdigga]

I bought one of those.  I had some trouble installing it as well.  I got the F2 version which has a clamp for the muffler-to-header joint.

Well, I must have gotten an F1 header because the muffler won't slip on all the way--the header outlet is too big (or the muffler inlet is too small).  Also the flange that mounts to the passenger peg is at the wrong angle.  I used a short bracket from my other exhaust to mount it.

It's not perfect but it seemed to work out well enough.  Come springtime I'll have to take it to a muffler shop to have the muffler inlet expanded just a touch.  It might ruin the chrome but I'd prefer it to fit with no leaks than look pretty.

[Geeto67]

Actually I think you are having the exact reverse problem I am having, mine slips all the way down the header but it is still not enough.

Looks like you have an f0/f1 header with an F2 muffler on a K frame.

Rear exhaust mount is different on K anf  F bikes.

Header pipe is different between f0/f1 and f2/f3.

I think I have had it too long to return it now (I bought it off ebay a couple months back and have already left feedback and such - to be fair it is not the seller's total fault since the mac box did have the F2 part number on it just the wrong contents inside).

Wanna trade mufflers?

of course I could just go back to my pacesetter monza dual outlet car exhaust tip, but they are a little too loud.

[jdigga]

I used to have a 4-2 system on there but I like how the F header tucks up neatly underneath the frame; 4-1 just seems tidier.  Thing is, it was hard to piece together a complete exhaust off ebay so I went with the Mac muffler.

So you have the F0/F1 version, without the clamp?  If so, sure--yeah I'm down for a swap.  But you'll have to keep your own baffle; I changed mine already.

[scondon]

 What baffle did you use, jdigga?  Ive got a Mac system I don't use because it's too restrictive, would be nice to open it up a bit.

[Jerry Rxman Griffin aka MuthaF'er]

I have one of these for my 75 750F0. Worked great. Looked good. Good chrome. Heavy gauge steel. No problem. Are they still available? I got the impression they had been discontinued by Mac. You can always remove the baffle and take the hack saw or drill to it. Cut it in half to get direct flow then reinstall. The baffle is a double pipe system with the pipes running side by side and not directly connected (if I remember correctly) which does not give a direct flow through path out the rear. Running Kerker now.

[mick750F]

What baffle did you use, jdigga?  Ive got a Mac system I don't use because it's too restrictive, would be nice to open it up a bit.

Jeebers scondon...Anything much less of a baffle in the MAC on my bike would be practically no baffle at all.  If memory serves we well there is only one offset baffle before the outlet. It's nearly a straight pipe as is. While okay at idle I find the system too loud under throttle for my liking. I'm looking to switch to a Kirker as soon as I can find a decent used header. I already have the muffler with one step above street baffle...1/4 comp?

   As to the subject of MAC in general...I've found their quality control to be less than acceptable. It was a real wrestling match mounting my head pipes...they didn't line up with the outlets properly...and the black finish proved to last a year before it started to rust.  Also, I had to grind down a couple of fins on my oil filter cover to mount it. 

Mike

[jdigga]

What baffle did you use, jdigga?  Ive got a Mac system I don't use because it's too restrictive, would be nice to open it up a bit.

I believe it's a Kerker replacement baffle, from another SOHCer.  Tone is a bit deeper.  However, I've heard the Kerker competition baffles and I really want one of those next season.

RxmanGriff: I tried getting mine directly from Mac but the order never got processed.  I got it on eBay.  My baffle was held in by one screw and popped right out; no surgery necessary.

[scondon]

What baffle did you use, jdigga?  Ive got a Mac system I don't use because it's too restrictive, would be nice to open it up a bit.

Jeebers scondon...Anything much less of a baffle in the MAC on my bike would be practically no baffle at all. 

    I know I must sound like a high decibal maniac. I don't know how long Mac has been in business but I probably have one of the first ever made. Come to think of it, I'm not even sure the baffle is removable. It has a very nice, quiet note. I got it off fleabay years back and assume it's a mac by comparing to old photos.I'll be shooting some pics tonight so might get one of my Mac? posted here.

EDIT:  Here is my ancient Mac. Despite the large opening it is very quiet.

[Geeto67]

I used to have a 4-2 system on there but I like how the F header tucks up neatly underneath the frame; 4-1 just seems tidier.  Thing is, it was hard to piece together a complete exhaust off ebay so I went with the Mac muffler.

So you have the F0/F1 version, without the clamp?  If so, sure--yeah I'm down for a swap.  But you'll have to keep your own baffle; I changed mine already.

I don't have a problem with keeping the stock baffle, I bought the thing to be quieter than the straight pipe on there now. PM me and we'll work out details.....

I really like the F head pipes too, although if I was going to do a 4 into 1 with a stock honda headpipe I would look for a 77/78 as they tend to be a little lighter (they don't have that stamped steel collector).

[jdigga]

Hmm, I'm confused now. 

This is my header and according to the parts microfiche this belongs to a 77-78 F.  Which would mean neither of our mufflers fit very well. 

[Geeto67]

I'm going to go out to the garage and check....I have both a 76 and a 78 header in there and I will get back to you

[mkramer1121]

jdigga,

Yours is a '77-'78 header.

[jdigga]

On one hand that makes me feel better than I have the header I thought I had, and that I got the correct Mac muffler.

On the other hand, the darn thing don't fit right!!! 

Geeto: I guess a swap won't do either of us any good then. 

[Geeto67]

eh..it was worth a shot....I didn't get a chance to compare headers yet, but muffler wise yours still looks different than mine and I can't figure out why. I'll just cobble it together and make it fit anyway.

[Jerry Rxman Griffin aka MuthaF'er]

That looks like the one I have for my 75F BUT I don't remember the reduction where it slips on. What is the inside diameter there? 

[jdigga]

The muffler you mean?  Appears to be 2". 

It's a tad shy of 2-1/8" which is the OD of my header:

[cben750f0]

if this helps the identification, these are the headers off my stock F1....

peace

[Geeto67]

figured out why the damn muffler wasn't fitting right....The PO had wrapped the header pipe outlet in 1/2" of exhaust tape. He did it so neatly that I mistook it for part of the pipe. Now the pipe slides on all the way. The rear mount doesn't line up at all (1.5" apart) but what do you expect from a cheap muffler.

[Jerry Rxman Griffin aka MuthaF'er]

ha ha ha     I'll bet that pissed you off more than originally. Makes me think you might have a 75/76 mufller instead of a 77/78. Mine worked fine. Holes lined up.

If anyone is interested there is a NOS 75/76 750F muffler on EBay at the present. I have only seen 2 of these in the last 3 years. Wish I had a NOS header to go with that muffler.

[Geeto67]

ha ha ha     I'll bet that pissed you off more than originally. Makes me think you might have a 75/76 mufller instead of a 77/78. Mine worked fine. Holes lined up.

If anyone is interested there is a NOS 75/76 750F muffler on EBay at the present. I have only seen 2 of these in the last 3 years. Wish I had a NOS header to go with that muffler.

I actually have a NOS honda muffler but I don't know what model it is for. I got it with this 78F and it is brandy new. Must have been made after 1980 because it has the emissions paragraph on it. It came wrapped in bubble wrap sans box so there is no way for me to identify the part numbers.

Does it line up with your stock muffler mounting bracket or the passenger peg hole. Mine doesn't line up with the passenger peg hole but it looks like it might with the original muffler mounting bracket.

got a pic?

[Jerry Rxman Griffin aka MuthaF'er]

Check it out here:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&viewitem=&item=330174432242

I'd have to rearrange a cold ass garage to dig it out. If you'd still like another picture I can shoot a close up in the next few days. Did you ever dig up that stash?

[Geeto67]

Did you ever dig up that stash?

Just got the last of "the stash" home two weeks ago and now I am going through the arduous task of cataloging everything. Last night I had a set of magnesium Kehin racing carbs on the work bench (no idle circuit) and was just marveling at how light they were. It will probably take me a good month to catalog everything that is there.