5 THINGS YOU NEED TO KNOW

Motorcycle News (UK) - - Garage -

1 Pri­maries

If you don’t get the de­sign of these cor­rect you’ll al­ways strug­gle. Length is critical and a big­ger bore isn’t al­ways bet­ter – imag­ine try­ing to wash your car with a 3-inch-bore hosepipe – it’s all about pres­sure. Some bikes have bal­ance pipes in be­tween the pri­maries, to re­duce pres­sure spots.

2 Si­lencers

These are ever more im­por­tant with trackdays hav­ing qui­eter noise lim­its in a bid to keep nearby res­i­dents happy. It’s all to do with how much sound-ab­sorb­ing ma­te­rial you can get around the in­ter­nal per­fo­rated pipe, so we use a slightly nar­rower pipe giv­ing more space for no no­tice­able power loss.

3 Ma­te­rial

Stain­less is not ex­pen­sive, easy to work with but can snap. Ti­ta­nium is light, but ex­pen­sive, time­con­sum­ing to make and hard to re­pair. A good com­pro­mise is stain­less head­ers with a ti­ta­nium si­lencer. Car­bon can’t be re­paired.

4 Main­te­nance

You should re­place the sound-ab­sorp­tion ma­te­rial ev­ery year on the ex­haust of a 1000cc bike, ev­ery two years on a 600cc ma­chine’s sys­tem. Use a good al­loy wheel cleaner to bring your stain­less sys­tem back to new, but be care­ful not to spill it on any car­bon fi­bre.

5 Per­fect ex­am­ples

OE man­u­fac­tur­ers are gov­erned by many re­stric­tions sur­round­ing emis­sions, space and noise when they pro­duce their sys­tems, but in my opin­ion the pre-2015 BMW S1000RR sys­tem was near on per­fect, the 2016 ZX-10R is good, and the cur­rent model R1’s has lots of room around it to keep it cool.

OE ex­hausts are gov­erned by leg­is­la­tion re­stric­tions

Big­ger isn’t al­ways bet­ter with pri­maries

Re­mov­able baf­fles are now a com­mon sight at trackdays

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