Shorty exhaust installed directly off of manifold?

[polyclot]

Is it possible to mount four shorty exhausts almost directly off of the manifold? I want as much clearance for the bobber frame as possible. Thought it might look cool too.

 

[polyclot]

 

[dirtdigger]

You will loose power with 4 short individual pipes. If the exhaust is too short you can do damage to exhaust valves when on decel, but mostly you will loose power and need to jet accordingly, more than likely you will have to go up a fair amount on the main jet because the engine efficiency is not good with that setup

 

[polyclot]

Right on. The only other Setup that i like is similar to this one pictured below. Kinda difficult without altering the frame it looks like.

 

[amc49]

X2, post #3................a pretty good power loss there, the shorter the pipes get the worse it runs. Looks are one thing but turning a decent running engine into a dog is another.

 

[polyclot]

Lol. That must be why nobody else has done it

 

[amc49]

Oh, I have seen people do it, there is ALWAYS somebody that breaks the rules of physics to bad result. I remember a guy who used to dragrace a Pinto with a 460 V-8 in it, sounded like utter crap and not long before he burned half the valves in it.

 

[toverley]

Since we are talking exhaust, I just installed a MAC 4 into 1. It now backfires on decell. I'm assuming that is because it is lean? Will it do any damage or is it okay? It is running well and I don't really want to mess with the jets.

 

[amc49]

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[amc49]

Did you renew the pipe-to-head gaskets? If reused they commonly don't seal then leak air at decel to pop in the pipe as the engine afterburns. Common for people to think lean but can do that if RICH too, if engine has not burned enough to then let the leaked air intermix to afterburn more. Same as an air pump adding more air to a cat in car to burn later in the pipe to consume all HC. Popping in pipe can be from either rich OR lean. Lean because lean burns too slow and keeps doing it in pipe, rich because may not burn all of it again to still be burning in pipe if you add an air source like manifold leak. Seen either way do it.

I see you are playing with a DOHC, the aircuts on carb stop that popping, if one bad or leaking then it pops. Look at the left side carb as sitting on bike, the two bolt cover on the side, that is where they are located, under that cover. In that case the aircut controls a second idle air restriction that gets cut off to richen the decel to not pop. An EPA thing since Honda made the idle so lean OEM. Richen up the idle mixture screws a bit and helps too.

 

[toverley]

New gaskets. Fixed. Thanks!