EXHAUSTS

[FIGHTERMC]

Hi,i'm seeing a few bikes{fighters} that have slash cut pipes
on them surely they can't be good for the engine or
can the carbs be setup for this,i'm not really cluded in to this
so any advise would help as i'm thinging of putting one on the blade if it works fine.

[Jockney Rebel]

good question m8 i was thinkin the same thing.....

[shift1313]

there is alot of physics involved here but ill say a little bit about the subject.

Each bend in your motorcycles stock exhaust is tuned. every time your exhaust valves close it sends a pulse down the exhaust tube and at each bend it reflects back a negative pulse. These are timed with different lengths to help scavenging which "pulls" the exhaust gas out of the cylinder if timed right. This is why yamaha uses their exup on most sportbikes. This is just a valve in the exhaust which changes the pulses to help scavenge. This is why alot of streetbikes that have exup loose low/mid power when they replace it with a full system but might pick up total high rpm HP.

Diameter makes a difference. Smaller pipe allows the exhaust to travel faster at lower rpm helping out torque. Larger pipes flow more at high rpm helping up top HP but sacrifice low end.

Backpressure is also important but only to a certain extent. The reason you burn valves when you run shorty exhaust is because you arent dumping enough fuel in the motor. The reduction in back pressure causes more exhaust gases to flow which will cause a lean condition. This is only true to a certain extent. You do want some decent length of pipe on your bike but as long as your carb is jetted right you shouldnt have to worry too much about burning valves. After exhaust work, taking plug readings is a good idea just to make sure you arent running hot. If your plugs are extremely white you are way too lean, if they are a very light brown then your are running in the 17:1 range and need to add a bit more fuel. Probably one size on the mains and raise your needle up 1/2 clip or 1whole clip.

If you want to run pipes without mufflers you shouldnt have a problem(beside the raspy noise). Im going to run baffle cones in my exhaust and might taper down at the outlet. Right now i run 4-1 with a 2.5" outlet but im going 4-2 with 1.5 or 1.75" outlets.

[FIGHTERMC]

Thanks for the info Mate,i got a pipe made up yesterday and i'm going to run a baffle in
it and theres a guy that my mate knows that will jet it for me so hopefully
it will run right.
rgds
mc

[Jockney Rebel]

my pipe is a copy of a marshall deeptone system [i think] made by a firm here called o brien im told] it has a 2" pipe after the collector widening to a 3" cone i wanna replace it with a yoshi fs3 can which ive got in the garage waddya reckon , i dont have any headers to go with the yoshi but was thinkin of adaptin the exsisting ones

[zx12argh]

I had a stocker zrx1200 - put a yoshi rs3 on the end - I thought it ran sweet - had a nice burble and crackle to it
Then I rejetted and k&n air filter - the difference was astounding. It gave the sweetest throttle response and power delivery.

but then that weekend I got hit by an old guy on the way to church - his fault. That was a year ago and my knee is still fucked up. Bitter me? nope.

[Jockney Rebel]

ta pete
yoshi it is then..... just gotta find a connecting pipe for it and keep it far enuf off the ground

[shift1313]

whats the dimmensions on the yosh? is it 2" inlet and 2" outlet, what about the thickness of the packing inside. Typically going from a magaphone setup down to a straight through you will loose some top end power but pickup some mid range and low end tq. This is especially true if your muffler outlet is smaller then the inlet. This will also make it quiter. This is why alot of pipes have different end caps for tuning.

another note. That pop and crackle on the bike is running lean. It sounds cool and most vehicles do it a little on decel once theyve been modded, especially without the propper jetting, but its a good indicator that atleast your pilot circuit on your carb is lean.