Fitting an exhaust..

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Information provided by Gary...

One of the first things most of us do when we get a bike is change is the exhaust – fitting either a can (more usually a race than a

road-legal item), or a full system. The legal aspects of this are covered in MOTs, so let’s look at the why and how of changing your

exhaust plumbing.

Take, for example, a Yamaha R1. When you’re riding a 140bhp monster of doom, you don’t really want it to sound like an environmentally

over-friendly 4bhp lawnmower. So you decide to fit an aftermarket can to savour the sounds and (you hope) liberate a couple more horses

through the rev range. Fine.

Before you take the can out of the box, take the instructions out of the box. And read them. Whaddaya mean read them, it’s a can – you

take the old one off and put the new one on. Granted, but the mounting bracket will be different, it might bolt inside or outside the

hanger, there will be different washers, the collector clamp might fit one way and not another.

It sounds tedious and it is, but it’s nowhere near as boring as rushing into things and then having to do it all again when nothing fits

and exhaust gas keeps blowing out of the collector/can joint because everything’s on the piss and won’t clamp tight. And then you’ll have

to read the instructions anyway.

So, you’ve read the instructions. Make sure you’ve got the right tools, i.e. spanners, and possibly Allen keys that fit, and

get on with it. Check that nothing fouls the pillion

footrest or the swingarm. Check the pipe exit doesn’t direct fierce exhaust gas straight onto your right rear indicator or numberplate,

and then fire it up. You might not need a dyno run, if that’s what the manufacturers reckon, but you might want to double check that

everything’s OK in the fuelling department anyway.

For a full system, the same method applies. Except this time, loosely assemble the full system away from the bike. This is to make sure

(a) there are no parts missing, and ( it all fits together perfectly. If there any burrs on the joints, now is the time to dress them with

a file and a bit of emery, not later when they’re underneath the bike and you can’t get to them properly.

Take anything off the bike that looks like it might get in the way. That means the fairing, radiator and maybe the oil-cooler. Make sure

you know if the centrestand (assuming there is one) can be retained or not. Make sure you know which header pipe goes to which

exhaust port. Offer everything up first in a dry run. If it all goes together real nice, do it for real.

Gently flick the old exhaust gaskets out with a gash screwdriver, clean the ports with a bit of contact cleaner and check the studs are

secure and the threads are in good order. Blob a bit of high-temp grease on the new gaskets to hold them in place, and then loosely bolt

the header pipes to the cylinder head.

Now fit the collector box, sliding the exit ends of the header pipes into it with a bit of high-temp grease, now fit the can, but don’t do

anything up more than finger-tight for now. If there are tension springs to fit to any joints, use a proper spring-puller for them,

and that doesn’t mean a bit of welding rod wrapped round a stick.

Now tighten all the bolts and clamps, use a torque wrench where a torque setting is specified, refit/refill radiator and oil-cooler where

necessary and start the engine. Rev it gently because the carburation might well be all over the shop and check for leaks. Get the system

hot, let it cool down again and then re-check all joints, clamps and bolts.

Minor leaks usually seal themselves through carbon build-up, but if you can hear anything blowing, it’s back to square one. Then put the

bodywork back, make sure nothing fouls, then head off for a fuelling check on the dyno and marvel at the massive power gains,

the wholesome noise and your dented wallet.

Edited January 9, 2007 by vicki

[Guest]

That reminds me ive still got my header gaskets to fit