Author Topic: '78 CB750F Exhaust megaphone has a hole the size of Texas in it! (Read 2424 times)

Hondalubr · « **on:** September 05, 2005, 10:47:18 AM »

OK, I have looked on this forum and others about trying to fix it but I have not seen anything similar to my problem yet so I figured I would post.

There was a glaze of this black fiberglass-like tape stuff around my pipe just after the header clamp to the magaphone muffler. I decided to investigate. The headers are in fine shape. No rust at all. I removed this fiberglass and I could hardly believe the muffler was still on the bike. The metal was missing all the way around and then it turned and went about 6 inches towards the tip on the underside of the muffler.
What are my options? I don't want to go with straight pipes. I like loud but I have a neighbor who will call the PD at the drop of a hat. Does Honda still make this trumpet, or do I need to go aftermarket? Can I fix this? If I have to go aftermarket, what make and model would be closest to stock in look and performance? I do not want to re-jet if possible. I have 105/35 jets now, which is stock. I do not own a welder of any type, so unless I take it to a welding shop, that is out of the question. Are there any products out there that would do a better job than that black stuff the PO slopily put on?

Your replies are appreciated as I am still a newbie.
Have a good day and keep your rubber to the road,
Mike

DammitDan · « **Reply #1 on:** September 05, 2005, 12:52:18 PM »

Remember, Ebay is the red-headed stepchild if it comes down to it...

scondon · « **Reply #2 on:** September 05, 2005, 08:35:24 PM »

More than a few of the 78 750F pipes I have seen are rotted out in the same spot. The "quick fix" would be to use muffler tape and sounds like that's what the PO did on your bike. I saw one yesterday that had a metal sleeve welded on and it looked pretty good, I'd go that route if you want to keep the stock look. Otherwise, there are a few "universal" type exhausts that will fit. I had a cheap one from Emgo that actually sounded pretty good and, though shorter, looked pretty decent.

Heres the Emgo at Dennis Kirk:

http://www.denniskirk.com/jsp/product_catalog/Product.jsp?skuId=446993&store=Main&catId=403&productId=p446993&leafCatId=40302

kghost · « **Reply #3 on:** September 05, 2005, 08:48:44 PM »

Bet it looks just like this one........

Hondalubr · « **Reply #4 on:** September 05, 2005, 10:45:07 PM »

Yes it does kghost. Except there is a right hand turn towards the tip that goes for about 6 inches.

Thanks for the link scondon! Do I have to alter that pipe at all to make it fit my bike? IE the bolt holes etc... Or will it just bolt right on. I like the look of that one too. It says it does not conform to EPA noise levels for later years. Does that mean it is pretty loud?
You know what I hope it is louder... Screw my neighbor!
Mike

CB750F2 · « **Reply #5 on:** September 05, 2005, 11:40:07 PM »

I have a similar bike to yours and right now I am reparing my muffler which is rusted out similar to yours. I will be welding in a sleeve in a similar manner described by "Scondon". It is not an easy job and you need access to MIG and/or TIG welders. JAMA is brand from Holland which makes replacement mufflers for our bikes. I have attached a PDF file for you to look at. I have no idea of the quality but they retail for around $600.00AU for us in Australia. Hope this helps. Pat

Hondalubr · « **Reply #6 on:** September 06, 2005, 08:38:49 AM »

Quote from: CB750F2 on September 05, 2005, 11:40:07 PM

I have a similar bike to yours and right now I am reparing my muffler which is rusted out similar to yours. I will be welding in a sleeve in a similar manner described by "Scondon". It is not an easy job and you need access to MIG and/or TIG welders. JAMA is brand from Holland which makes replacement mufflers for our bikes. I have attached a PDF file for you to look at. I have no idea of the quality but they retail for around $600.00AU for us in Australia. Hope this helps. Pat

Thanks Pat,
I will check it out here in US for prices and availability. As for the welding... I could weld it myself but I do not have the proper tools. IE welder etc...
Mike

scondon · « **Reply #7 on:** September 06, 2005, 09:30:35 AM »

Quote from: Hondalubr on September 05, 2005, 10:45:07 PM

Do I have to alter that pipe at all to make it fit my bike? IE the bolt holes etc... Or will it just bolt right on.

I believe that the header has a 1 3/4" diameter. The exhaust in the link I posted says it fits 1 1/2- 1 3/4" exhaust and comes with a "reducer", so I'd assume that it would fit the header with no mods. I'm not sure that ANY aftermarket exhaust will bolt straight into the rear bracket, but most should come with extra parts to attach either to the bracket or reat foot peg mounting.

eldar · « **Reply #8 on:** September 06, 2005, 09:46:17 AM »

You can also get many mufflers with removable baffles. SO this way you can annoy your neighbor and if he calls the police, you still have your muffler on!

Hondalubr · « **Reply #9 on:** September 06, 2005, 10:13:20 AM »

Quote from: scondon on September 06, 2005, 09:30:35 AM

Quote from: Hondalubr on September 05, 2005, 10:45:07 PM
Do I have to alter that pipe at all to make it fit my bike? IE the bolt holes etc... Or will it just bolt right on.

I believe that the header has a 1 3/4" diameter. The exhaust in the link I posted says it fits 1 1/2- 1 3/4" exhaust and comes with a "reducer", so I'd assume that it would fit the header with no mods. I'm not sure that ANY aftermarket exhaust will bolt straight into the rear bracket, but most should come with extra parts to attach either to the bracket or reat foot peg mounting.

I will measure it to make sure and then contact the site to see what actually comes with it.
Thanks again scondon!
Mike

Hondalubr · « **Reply #10 on:** September 06, 2005, 10:19:45 AM »

Quote from: eldar on September 06, 2005, 09:46:17 AM

You can also get many mufflers with removable baffles. SO this way you can annoy your neighbor and if he calls the police, you still have your muffler on!

Is it legal to run your bike in California without the baffles??? If so... Screw that neighbor. I am gonna go out every night and rev that sucker 'til 9:59PM LOL
That'll fix him. You ever see that movie with Richard Prior where he buys this house next to a really annoying neighbor. (The name of the movie escapes me right now.) I feel that way about this guy in particular. Except, he is nice to your face and them goes inside and calls the PD for stupid Sh@&! He isn't man enough to say something to my face, if he don't like something. I guess that's probably because I would tell him where to go if he did. LOL
Mike

eldar · « **Reply #11 on:** September 06, 2005, 04:01:44 PM »

Well it may not be legal to run without baffles but how are they going to check??? It is not like you are removing an outside section of the muffler. You pull a screw out and the baffle comes out and you really cant tell.

Hondalubr · « **Reply #12 on:** September 06, 2005, 08:35:23 PM »

Quote from: eldar on September 06, 2005, 04:01:44 PM

Well it may not be legal to run without baffles but how are they going to check??? It is not like you are removing an outside section of the muffler. You pull a screw out and the baffle comes out and you really cant tell.

Alright, just so I know what I am getting myself into. LOL

Also, Dennis Kirk is out of those universal exhausts, does anyone recommend another store or brand?

Mike

TwoTired · « **Reply #13 on:** September 06, 2005, 11:05:50 PM »

Just a word of caution. (Wet blanket for your fire, I suppose.)
The 78 Hondas were designed to burn lean as a concession to Anti polution proponents. Changing the restriction or flow characteristics of the exhaust system may well require compensating the mixture ratios in the carbs. If reading the experiences and actions taken of others on this list with bikes similar to yours is any educator, you may have to change your main jet, slide needle, and slow jet to return the engine to correct running tune. The more open and loud your replacement exhaust is, the more drastic the changes to mixture ratios are likely.
FYI

eldar · « **Reply #14 on:** September 07, 2005, 01:57:13 PM »

Heck I got a 78k and the exhaust needs to be sealed yet and I have problems running too rich. But

eldar · « **Reply #15 on:** September 07, 2005, 01:58:31 PM »

DAMMIT!
Continuin from last post, I still have to do a full carb tune so. I got emgo slip ons from jcwhitney. Megaphone slash!

Hondalubr · « **Reply #16 on:** September 07, 2005, 05:34:31 PM »

Quote from: eldar on September 07, 2005, 01:58:31 PM

I got emgo slip ons from jcwhitney. Megaphone slash!

How do they sound? a deep rumble or quiet?
I saw the slash on dennis kirk, and they looked pretty nice.
Mike

eldar · « **Reply #17 on:** September 07, 2005, 06:11:53 PM »

Well since I dont have my exhaust sealed yet, it is hard to say. But right now they sound ok. Not loud but then I am on my bike when I hear it so it may be louder than I think. Actually reminds me of the stock pipes.

Hondalubr · « **Reply #18 on:** September 07, 2005, 07:27:31 PM »

I am thinking of going with a Dunstall type pipe. scondon gave me another link that I was able to find them on. I like the stock look. They also say they are quiet like the original pipes but they still have that removable baffle too. My neighbor is gonna love me! LOL
Mike

Here is the link to the pipes he sent me. They are listed as universal exhaust.
http://www.oldbikebarn.com/motorcycle_parts.php?subcategory=Mufflers&bike=Universal

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Author Topic: '78 CB750F Exhaust megaphone has a hole the size of Texas in it! (Read 2424 times)

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