A question of cans?

[Scotty]

My trackbike used to have the secondary air system functioning, doesn't any more, didn't sound **** then, still doesn't.
During development the manufacturers spend ages working on the fuelling based on the specific back pressure generated by the standard exhaust, replacing the silencer with one giving less back pressure will obviously have an effect. Even when just fitting an end can the fuelling and thus performance can be improved by proper setting up using a dynojet kit/power commander. The effects of set-up are even more pronounced if using a less restrictive air filter and a full race exhaust system.
I've ridden my mate's ThunderCat and the benefits of it being set up correctly are very apparent, good response and clean fuelling throughout the rev range. For a not-so-new and relatively lardy 600 it goes surprisingly well.

[Jon_W]

I have to agree with Scotty in this. My Sv has been set up for race filter and slip on end can and the difference, especially on pick up, is notceable and there is no popping or banging.

[Mitch9128]

Sure you can dial it out, but popping/banging and crackling on the overrun are not signs your bike is running like ****, which is what Scotty originally said.

[Squashed_Fly]

Most of the bsb bikes at thruxton last year sounded awesome when they were popping coming into the corners. I don't know whether its good or bad, just that I love that sound! If it is bad though, why do the professional race bikes do it? Is it because they run higher octane fuel or something like that? Or is it just something you can't get rid of on bikes that run such extreme set ups?

[Squashed_Fly]

Interestingly though, the gp bikes at silverstone didn't seem too, just the superbikes...

[ro]

You can listen to various exhausts here.

I've always had stock exhausts on sportsbikes and never felt the need to change. But the previous owner of the DRZ400 I bought in the States had done lots of work on it including changing the carbs and setting up the jets for a complete Yoshimura system. Not sure I'd have spent that much for the performance increase it gave myself, but I must say sounds very nice. It's also rather loud and certainly attracts attention in traffic, which must be a good thing. Though coming home to a quiet neighbourhood late at night sometimes I wished it had a volume control! :-[

[Snowy]

My GS has popped and farted since the day I had it and this runs a closed loop fueling system controlled with O2 sensors and the ECU mapping so self adjusts for any changes. I have different headers/can/air filter/plugs/ from standard plus a secondary fuel mapping system and it still carries on the same popping on the overrun. It doesn't like too little backpressure though so prefers the can with baffle in. Runs great now all the way through the rev range and has much better low speed pickup than standard.

[redken1]

Since I fitted the Scorpion on the Fazer with no other mods I have certainly noticed a significant improvement in low and middle grunt. Prior to purchase, Scorpion assured me that the can was tested for my particular model and no mods would be required. It looks awesome and noise level is within the legal limits (with baffle fitted). Happy days!

[Dabz]

My street triple is a different animal with the baffles out - the extra torque at the lower rev range is incredible! BUT it does my head in after 10 mins, even with ear plugs in, so the baffles stay in :P

[NoYou]

Just dragging this back up because its been confusing me a while now, with a 4t does bolting on a more free flowing end can reduce the back pressure letting the scavenging of the cylinder more effective and therefore cause the bike to run rich?
I ask because it doesn't make sense to me that you would need to up-jet upon fitting a more free flowing end can, yet the "burbling" that results from not re-jetting is caused by excess fuel being dumped into the exhaust, surely that is an indication of it running rich, therefore requiring DOWN JETTING, not a symptom of running lean, which would require UP JETTING.

Or am i missing something here?

Trying to get my head around this 4t malarky after 6 months of near obsessive research into 2ts is baffling!