custom exhaust under engine question!

[zip70]

does it matter hoiw long the downpipe between the engine and the end can is? will it effect the power?

the reason i ask is that i wanna weld a stubby endcan onto the downpipes, just under the engine, in front of the rear wheel, know what i mean??

https://www.hondacb1.com/images/front9.jpg
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gixer 6

[Bezzer]

The short answer is Yes it will affect the power one way or another. There is a long complicated formula to determine the optimum length of an exhaust taking into account valve sizes and , duration of lift etc, the length and diameter of the different pipes and silencer you have etc, etc etc.

Practical answer is do it then get it put on a rolling road to check the power and also that the mixture is OK so at least you are not going to be causing any damage by running it way too lean.
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I used to be indecisive but now I'm not quite so sure.

[bish777]

Youll need to rejet! It will need much richer mixture than stock as the stubby is going to be far less restrictive.

If your making this kind of mod you may also want to drop your airbox, fit pods and go to a stage 3 dynojet kit, or a factorypro kit to suit.

It will be difficult to get right-you either fork out and get a pro to do it, or like me spend months fiddling and fine tuning.

in this order, set things up:

1) Ensure float heights are set correctly (as per your manual)
2) Select the right jet-the one that lets the bike rev freely and gives good power to the redline
3)Fine tune things by raising or lowering the needle.

Your plugs are a good guide as to the state of carburetion, your aiming for a nice light brown colour. If its black and sooty go leaner (smaller jet, or lower needle by putting the e clip in a higher notch). If the bike is running too lean the plug will look glazed, and go the opposite way.

Change the jet if no amount of fiddling with the clip height gets it running right.

If you are running very rich the bike will 'bog' down and youll get a wet note from the exhaust, a sort of flabby note. Lean will get you loud popping noises and the accelleration will be very lurchy.

If you get the stage 3 dynojet kit, id suggest as your fitting a fairly open pipe, use the mid size (marked 128) jet as a starter. As im using a road legal pipe i used the 124 jet. Bear in mind dynojet sizes are NOT compareable direct to kehin or mikuni sizes. the dynojet 124 is roughly a 144 mik jet and the 128 is a 150 i think.
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GSXR1100J

[epz]

why would you want to spew oil and water onto your back tyre?

also if its a yamaha i belive their exup valves add quite a bit of power to the bike

[Bezzer]

[sickpup]

I think it's a CB-1 not a CBR1.

[Kickstart]