Putting a short exhaust on motorcycle?

specify actual motorcycle and actual proposed 'short exhaust'. My old 1937 UL Harley ended up with drag pipes and sporty CH mufflers instead of longer stock pipes and muffler because for some reason there wasn't any stock pipes available anymore for the pre WW2 cycle. Lost points at vintage shows but passed police noise inspection. The old baffled 'shorty' muffler for Limeys were 1/3 the length of stock muffler and slightly louder but worked quite well if baffle weren't removed as was case on my BSA chopper when previous owner got his tickets- I used them awhile on R50/2 from police crash impound . A short but large diameter muffler for a 40 inch Kohler can be fitted on a couple cycles after a crash that rips up the stock and custom pipes, mufflers and it means the cycle can get home with minimal police attention, get ridden a month while money saved for new pipes, etc. I put on whatever fits and is cheapest available as needed--and if stock is still working then short, custom slipons are not 'needed',.leave it on.

No back pressure will increase fuel consumption weakening the mixture. In extreme cases the exhaust will glow cherry red for about two minutes before some vital part of the engine melts. Welding a washer in does not really help as the exact position is important. What happens is a pressure wave runs down the pipe and is bounced back the time/distance the wave takes to travels gives a maximum back pressure at a specific engine speed and at that point you get maximum power. The bike and car manufacturers spend a great deal of money on research. If it wasn't important they wouldn't spend the money. Most people when they hear someone go past think what a moron.

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RE:

Putting a short exhaust on motorcycle?

Just wondering if anyone would put a shorty exhaust on there motorcycle or if you would rather just put on a slip on yoshimura or two brothers exhaust?

Exhaust diameter and length play a big part of your motors power area.

Short exhaust(usually) are used in drag application. There is little to no back pressure. Meaning your low end(launch) will suffer. You may gain some in the top end depending on motor work done to the machine.

Really easy way to put it, ex: if you launch on the street rite at say 2000rpms. Put short open pipes you will be launching at 2500-3000 RPMs to get same effect. Now you can put small/short baffles in(or thumb screws) to gain some of the back pressure you need back.

Really unless you want me to get into a ton of science that I will probably waist my breath on. Just put a high flow air filter(k&n), and some slip on muffler. Rejet or reprogram as needed.

Depends on how loud you want it, and the state regulations on loud pipes. If the pipe are short enough they may burn your legs. My pipes go all the way to the back on the custom. THe long straight lines of the long pipes make it look great and sound wonderful (Yamaha Warrior 1700cc / 102ci.) SOme short pipes make bikes annoying to the public and attract attention; usually the wrong kind. Your choice.

The Tramp

actually if you use an anti reversion cone at the header pipe [basically a ventouri] you will lose zero performance even with a thirty inch drag pipe. problem solved bring on the short pipe with no baffles!

what for - so that you have to change the remaining bike to suit?