Stainless Exhaust - I Should have resisted

[roadster]

But I just had to get rid of the large black lump on the CB300R

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This rear box is from SP Engineering and although the material quality and construction are very good the noise level, even with the DB killer provided, was totally unacceptable. I have added two extra baffles, one front end and one back end and its now reasonable but sadly if the performance has suffered I'll have to go back to the Honda lozenge. The issue is that the original includes a catalytic converter matrix which does a lot to cut the noise. The weight saving is around 2Kg.

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[Skub]

Looks tidy. SP Engineering make good stuff.

[A_morti]

https://www.ebay.de/itm/266028303116

You want one of these, or something just like it. It's basically identical to the catalyst you get from akrapovic or whoever, if you add that to your race system as an option.

I put same on my cb300r and it really knocked the edge off the sound, and also deleted that vintage unburnt fuel smell you get with removing the cat.

[The Spin Doctor]

That's the problem with trying to beat the bike manufacturers... it's not like it was back in the late 70s and early 80s when little effort was made to create good gas flow with some silencing through the OE pipe and pretty much anyone who could roll a tube could make an exhaust which produced 10% more power...

Scorpion keep releasing data for their pipes which they claim produce more power than standard... it's often just a couple of % up, and they're not road legal either since they ditched the cat.

Does look MUCH nicer though.

[Le_Fromage_Grande]

Looks nice, but I don't think I've had a bike built after 1986 where an aftermarket exhaust worked better than stock.

[Yorick]

Looks nice, but I don't think I've had a bike built after 1986 where an aftermarket exhaust worked better than stock.

I've had Yosh cans on a few of my GSXRs. I can feel the difference

[Le_Fromage_Grande]

Looks nice, but I don't think I've had a bike built after 1986 where an aftermarket exhaust worked better than stock.

I've had Yosh cans on a few of my GSXRs. I can feel the difference

It's easy to feel when something is noisy and slower, Yoshi can easily knocked 10mph off the top speed of my YZF750, but it sure looked pretty

[Skub]

When you decat a bike it needs to be properly set up for the new system.

[A_morti]

I've had Yosh cans on a few of my GSXRs. I can feel the difference

And you typically rode those sedately round town on part throttle. Right?

It's (probably) still possible to make a straight through pipe which will flow more at the top end and some bikes may still have enough wiggle room in the standard lambda sensor to use it, but everything else is less easy nowadays, because the efi and exhaust are developed as one.

I reckon the only time you'll get a real benefit from an exhaust on most bikes is either with significant Dyno time from someone who knows their shit, or if you also fit a power commander or similar with a wideband auto tuner.

[Le_Fromage_Grande]

My GSXS 750 is noticeably slower with the noisy exhaust (that came with it) on, you can feel it's running lean at high rpm, the mid range was fine, but it was ear splittingly loud, and that was with the baffles in.

My old Kawasaki, on the other hand, produces max power at 8500 rpm (120 bhp) so you don't have to worry about the exhaust working over a wide rev range, and almost anything works in it.

[roadster]

Now I've been for a more comprehensive test run things are not looking/sounding too bad. The little engine is still pulling really strongly from 4000 rpm and in town this means 5th gear can be used to keep the noise very reasonable. It still runs up to well over 9000 rpm easily and that means motorway speeds and lively overtaking when needed.

Inside the silencer things get very hot and I have had to reject my first assembly idea because the spring I put between front and rear baffles to stop any rattling very quickly lost its temper and collapsed! Provided the other internals survive better I might be able to stick with it.

[Le_Fromage_Grande]

If it's getting very hot it's running lean, if it runs too hot for too long it will destroy the exhaust valve, hole the piston or both, if you want to keep the can on get the bike set up on a dyno by someone who knows what they're doing.

[Bigjawa]

Now I've been for a more comprehensive test run things are not looking/sounding too bad. The little engine is still pulling really strongly from 4000 rpm and in town this means 5th gear can be used to keep the noise very reasonable. It still runs up to well over 9000 rpm easily and that means motorway speeds and lively overtaking when needed.

Inside the silencer things get very hot and I have had to reject my first assembly idea because the spring I put between front and rear baffles to stop any rattling very quickly lost its temper and collapsed! Provided the other internals survive better I might be able to stick with it.

The baffles will be getting hot, on my K12 with the straight through can, you can sit at 100 all day and the can will be cool enough to touch for a while. On the standard can with the cat, you can look down it at night and the thing is glowing inside, my flir thingy tells me the external temperature is well over 100c.

[Mr. Dazzle]

If it's getting very hot it's running lean, if it runs too hot for too long it will destroy the exhaust valve, hole the piston or both, if you want to keep the can on get the bike set up on a dyno by someone who knows what they're doing.

Bear in mind modern bikes are specifically designed to get the exhaust hot so the catalytic converters "light off". Indeed that's one of the big reasons lots of bikes have short stubby exhausts down the bottom now, double whammy of heating up quicker and keeping the really hot bits out of the way.

[ZRX61]

Looks nice, but I don't think I've had a bike built after 1986 where an aftermarket exhaust worked better than stock.

Muzzy Megaphone on the '99 ZRX11. Entire system weighs a hair under 9lb, stock system was 30lb.. so based solely on the 7lb = 1hp formula it gained 3lb just from the weigh savings.

& the stock system was a frigging cork. I fired it up with the muffler off & it made less noise than the wifes '78 KZ1000-A2 with a Kerker K2 on it.

[ZRX61]

If it's getting very hot it's running lean, if it runs too hot for too long it will destroy the exhaust valve, hole the piston or both, if you want to keep the can on get the bike set up on a dyno by someone who knows what they're doing.

It can even cause the valve seats to fall out of the cylinder head. Idiot pilot did that on the Tigercat, I still have the jug somewhere complete with valve jammed open by dislodged valve seat.