About 750 stock exhaust

I'm curious if anyone has a cutaway pic, or diagram, of the factory mufflers?
I'd like to know what exactly they look like inside, and I do have a reason.

My new 750 has factory pipes, that the openings on the back look like someone cut them out bigger. With a flashlight, I can see at least one baffle, just a disc with I think 4 holes drilled through it , no glass packing, and it's loud. Has anyone here repacked a factory muffler?

What's the final exhaust port supposed to look like? Similar to the 650?

Could this be a contributing factor to very sooty plugs? I know if you change to aftermarket exhaust, you need to change jets.
I'm assuming if somebody modified the stock exhaust, the same problem would arise?

I'll take and upload a pic of my pipes after work today.
Thanks for all the sage wisdom I'm sure you all might be able to offer!

 

I don't have a pic but I can tell you basically what's in there.

There are at least two, maybe three internal baffle plates. Two of them are connected by three or four tubes running between the two plates, then the rearmost baffle supports the other end of the "exit tube." I've never seen any that had any sort of packing in them.

This is just a general description based on looking inside rusted-out 550 mufflers; the actual design varies slightly from bike to bike I'm sure. But they basically work like OE-type auto mufflers, relying on a series of baffles and offset tubes rather than any "packing."

 

I have photos of the inside of a Maxim-X muffler, it could give you an idea, even if I doubt they are similar.

 

I hope this link will work

http://tinyurl.com/pd8c3m5

This muffler came to me without the end cap plate, so it's pretty clear how it is made inside. The empty hole on the left is for the final outlet. It was probably just long enough to go from between the last two plates (there are three of them plus the end plate) and the outside, so I'd say eight inches long.

First plate when the exhaust gases enter the muffler is actually a deflector that blocks 2/3 of the section. There are two or three small holes in the plate. Then , there is a tube running from the second plate to halfway between the third and the end plate, so that a part of the gases hit the end plate and have to go back between plates 2 and 3 through two smaller holes, and only then they can exit through the final tube. All of the internal plates also have small holes.

If you look at the previous picture in the album I linked to, you will see the plates locations by the welding spots on the outside of the muffler.

 

Thank you for the info and pictures!

I can only use my cell phone for internet at the moment... can't upload photos until I get it fixed.

However, looking into the opening of each exhaust isn't too reassuring. =(
It looks like somehow, all the pipes running between the baffles were literally ripped out.

I'll post the pics as soon as I get my home internet fixed tomorrow.

So, could this cause the same problems associated with changing exhaust?

 

Many other factors could explain your sooty plugs: dirty air filter, enrichment circuit not working properly, mixture screws misadjusted, poor spark.

If your mufflers are too much straight through, it would lean out the mixture, not the opposite.

 

Okay. I guess I'll add that to the list of replacement items. I was excited because the pipes are pretty rash free, no big rust holes.. should have looked inside them first.
It seriously looks like someone reached into the right pipe somehow and pulled all the tubes out.

I have a feeling I'm eventually going to be giving Chacal more of my money than I was expecting. =)

Ughhh... Okay, so if I eventually go aftermarket exhaust, how in the hell do I even begin to calculate what size jets I would need? Please don't tell me it's guess and check.

Are there any known slip on mufflers (my headers are fine) that have the same flow resistance and volume as the factory, so no rejetting would be needed?

 

Your bike has a "collector box" exhaust system; so pretty much any mufflers you install will be pretty much plug-n-play as long as you keep the stock headpipes and collector box.

 

Bigfitz is right. I put cheap aftermarket mufflers on my Maxim-X years ago and it ran OK without any rejetting. The important thing is the collector box between the headers and the mufflers.

 

That's great to know! I was intrigued as to why the four headers flow into one area, then back into two pipes.
I assume then that the collector acts as a bottle neck, keeping the pressure in the headers up semi-regardless of the mufflers behind the box?

Similar topic, different question. Is it true that wrapping the header pipes can cause them to wear faster from the excess heat?

Thanks again for all the help!

 

I think the collector box is supposed to equalize the flow from the headers. It has something to do the firing sequence. If every header has its own muffler (like the old Honda CB750) there would be no need for a collector box. This said, the systems that don't use a collector box usually have a cross-over pipe for the same reason.

Wrapping is just a cheap way to hide rust, in my opinion.

 

Yamaha's collector box contains some form of magic.

And I have to agree on pipe-wrapping; especially on dual-walled pipes like our stock ones are. The dual-walled head pipes negate any possible advantages to wrapping other than "cosmetic."

 

I didn't realize the pipes were dual walled.

I personally think the white pipe wrap, once it's been heated enough to turn that off white almost bronze color, is absolutely beautiful on header pipes. Or even just the bronze colored wrap. I also figured that it would be a semi-protective cover on my pipes.

My plan was to properly ceramic paint and bake the header pipes, then to wrap, eventually, figuring that might make the unit last even a little while longer.

I also very much dislike "bumper" chrome, generally, in case you are wondering what's wrong with me.

 

The inside of the right side muffler;