underbelly exhaust ideas ...

[justanothernoob]

My FZS came with what claims to be a gixxer exhaust that's clearly had the baffles removed. The whole thing is a bad fit and leaks and pops ... although the sound does put a grin on my face at 5-6000 rpm and again at 10000

I'm going for minimalistic on this bike so I'm looking into swapping the exhaust for an underbelly one. There don't seem to be any off-the-shelf solutions out there so I thought I'd run some ideas past The Collective and get your thoughts.

Key goals are minimalistic, not raspy sounding, not overly obnoxious. I know, a lot to ask when shortening things ... but I figure that the current exhaust has no baffles so I probably can't get any worse. And I've tried it without any exhaust at all and it's not that much worse than it is now. So I'm pretty sure that whatever I do will be an improvement.

So while I'm experimenting my thoughts are to keep the costs down. So I'll grab a cheap exhaust off aliexpress. I know that you often get what you pay for so I'm aware that:

• the exhaust won't be the akrapovic or yoshimura that it claims to be!
• it might not do as good a job of muffling as the genuine article but it'll be good enough
• at least they will have done the hard part: shaping the exhaust muffler in a puurrrrrdy way rather than my bodged and dented fabrication skills!
• I can always modify it with longer baffles or extra glass-packing if needed

This photo shows the amount of space to play with.

The larger measurement is 360mm and the smaller (y-section for the 4-into-2) is 80mm.

Details exhaust ponderings ...

exhaust ponderings ...

I'm thinking that I'll need to cut out the y-sections that take it from 4 into 2 and re-weld those closer to the down-section. Then I can slot in a short 270mm stubby exhaust and attach extra piping to the exit section to angle the exhaust away from the rear tyre and out the side of the bike. I'll then hide all of that with a belly-pan.

Also wondering if there's any reason not to reweld the y-sections actually on the down-pipes before they bend to run parallel with the bottom of the bike's frame? That might allow me to use a longer muffler and reduce the sound some more.

I've attached a link to the sort of exhaust that I'm thinking of from aliexpress (I hope that doesn't break any house-rules).

The kind of sound I'm aiming for can be seen at this link - not a Fazer but still an inline 4, albeit with very fat pipes!  I like the Maverick at 1:33, the Two Brothers right after that, M4 at 3:55, GPR at 4:25 and the Arrow at 7:40.



Here are some pics of the Z800's downpipes. I might get some custom ones made up in which case I guess I could always bend back towards the front wheel like the Z800 does to give more room for the muffler.

Details Z800 decat exhaust

Z800 decat exhaust

Details Z800 exhaust - side profile

Z800 exhaust - side profile

Appreciate people's thoughts. Very much aware that what I'm proposing is outside of the square and might be seen as breaking the rules. But keen to hear opinions from people who have experience with this sort of thing. Not so keen on the wild speculation or fear of the unknown and "leave it the way the manufacturer made it, they know best" because ... well, how the manufacturer shipped it is always just a starting point!   

I got this bike REEEEEEEALLY cheap, so I don't mind spending a bit of dosh on it to get the desired result - it will still be far cheaper than having bought something else.

Cheers y'all

David

[joebloggs]

I've seen a car type rear box fitted under there which exited underneath the footrests. Work in a min so will have a look for it later

[justanothernoob]

yeah I was wondering whether something like that might work. I might have to remove the centre-stand to create a bit more space (which isn't the end of the world as the shortened dog-bones will make that redundant anyway). Would be great if you're able to find those pics

[joebloggs]

Google Sasha lakics ready to race cx500 cafe racer

[justanothernoob]

wow! that's a cracking bike - thanks for digging that out, Mister Bloggs - love the sound of that V-twin - takes me back to boyhood dreams of being a WWII Ace in a Spitfire 

That approach would fit under nicely - now to go investigate where to find / how to build one. I'm guessing there's a bit more to it than a hollow box or am I over-thinking it?
It looks like both down-pipes feed into a common chamber but I wonder how they channel the muffling?
Are we talking something as simple as this - packed with glass? (excuse the rough sketch - I couldn't find a fag packet so had to make do with a napkin  )

Details exhaust concept 1

exhaust concept 1

[joebloggs]

wow! that's a cracking bike - thanks for digging that out, Mister Bloggs - love the sound of that V-twin - takes me back to boyhood dreams of being a WWII Ace in a Spitfire 

That approach would fit under nicely - now to go investigate where to find / how to build one. I'm guessing there's a bit more to it than a hollow box or am I over-thinking it?
It looks like both down-pipes feed into a common chamber but I wonder how they channel the muffling?
Are we talking something as simple as this - packed with glass? (excuse the rough sketch - I couldn't find a fag packet so had to make do with a napkin  )

Details exhaust concept 1

exhaust concept 1

Find an old car back box and cut it up, that will give you an idea of what you need to make.

[justanothernoob]

Thanks Joe - Cracking idea, I'll give that a go - and it means I get to tear stuff apart 

There's also the Ixil SX-Xtreme (think it's the same as the SX 1) - as an out-of-the-box solution I reckon it would fit in nice and compact but I want a deeper growl. Might have to look at fatter pipes.

That Z800 has fat pipes too - plus a resonator. I'm wondering what effect it would have on back-pressure if I channel the exhaust down one side of the belly with a resonator, double back on itself back up the middle and then back again down the other side with the muffler. Kind of like an S lying on its side - with resonator at the top of the S and muffler the bottom. I seem to recall hearing somewhere that exhausts don't like u-bends so I'll pop into an exhaust place tomorrow and see what they reckon.

But for now ... time to go earn some $$$     (hate it when work gets in the way of play!)

[joebloggs]

Wouldn't worry to much about back pressure etc, if you want a tuned length stick with the original

[justanothernoob]

and then I saw a Buell XB12 ...