exhaust upgrades?

[metalzombievi]

hello, id like to get anyones input on the different types of exhaust.
which ones have you used and what did they do, add power, speed, what? who sells good quality ones and who to avoid. ive tried the "speed demon" exhaust and i think it cut down my speed and added a verry small ammount of power. i changed my exhaust because the stock one that came with the motor broke and was dripping oil through the welds.

 

[Deleted member 12676]

problem is that the tuning of the expansion chamber is out of tune with the engine and its max RPM.
A standard engine needs something around 30" from the piston to the beginning of the baffle cone (the final contracting cone) for the pipe to be in harmony with the engine.

 

[metalzombievi]

i bought the engine kit from venice motor bikes and on the websight it says that the engine is "fully balanced". i have no idea if it is. but if it was, would that affect the exhaust?have you tried different exhausts and have a preference?

 

[Deleted member 12676]

having a balanced crank has nothing to do with the exhaust.
yes I've tried different expansion chambers but not a single one that is sold for these bikes. Why? Because they aren't truly designed for these engines. They are designed for pocket bikes. Like the saying goes, if you want something done right you have to do it yourself. I designed my own expansion chambers based on my own pipe design program.

 

[metalzombievi]

so, one of these would work better than the other kinds of exhaust?

 

[HeadSmess]

They are designed for pocket bikes. Like the saying goes, if you want something done right you have to do it yourself.[/URL].

they arent even designed for them...short...they arent "designed" at all!

more, some lil asian "engineer" was told to make this "thing" that "looks like this" as "cheaply as possible". look at them closely and youll see theyre symmetrical in most cases... must have been easier to bore two identical tapers in two lumps of steel bolted together to make a press rather than change the taper for one side... and im sure the diameter is based on how many they can fit side by side on a standard sheet of steel rather than whats actually required for performance.

sure, they do have some effect simply due to the shape but thats just sheer coincidence.

agree with all the rest.

make them yourself. to the design calculated by various port timings and other niggly little factors. each and every angle and diameter in the pipes is critical. that 30" length is a good approximate for 7000 rpm or so. the length stays much the same on most engines... shorter is faster, longer is slower(rpm)

and be prepared to make a LOT of pipes, chasing dragons this one you forget to compensate the diameter, that one you didnt have enough bends and its got bad flow just when it starts hitting band, this one...well this one im keeping but maybe if i just tweak that reversion cone a tad?...that sorta idea

dont bolt things on hard or they break. pro pipes on gokarts motos, etc are all spring mounted for a reason.


there may be some merit in using and modifying one from an old dirtbike, but only if its a similarly sized engine and you sorta understand what they do.

the pictured "poo poo pipe" is just a long header. constant diameter. great for a fourstroke and might cause a bit of band in a 2stroke, but not much.

they look like well fed leeches on two strokes for a reason

 

[Deleted member 12676]

HS, I couldn't of said it any better.
I was giving them too much credit by saying they were designed. ha!