Tuned pipe and carb question.

[justin86]

Sorry for all the questions quys But I want to do this build realy well, so I want to take advantage of your knowlage and not just rely on y own theories.

First of my motor is a current model suzuki 4hp two stroke piston ported motor ex lawn mower motor with only a couple hours use. I believe it is 160cc.

I will run it with a megaphone, so does anyone know of a calculator for designing the megaphone(not a full tuned pipe)?

What is better for the megaphone/pipe, stainless or steel?

I have had and worked on two stroke motorbikes of this size, and the carburetors were bigger, so I believe this is quite restrictive.
I would like to change to a diapram type carby, maybe walbro or something similar, can anyone recomend a carby? a link?

Now I can cast/fab a intake tube, but how much of a difference to power could it make with a longer tube? I am not sure but I think this could make a difference. What about material, cromed mild steel or polished aluminum for the manifold?

About crank case stuffing, could I use solder? as I want it to be reversable.

Stuffing will make it rev faster (I believe) but will I have to combine it with a domed piston? or is it ok as is?

Photos of the motor are here http://www.diygokarts.com/vb/showthread.php?t=8165

 

[Kaptain Krunch]

For the megaphone, i have no clue about a calculator, but I'd say stainless would be better just for the rust factor.

Carbs. Well, obviously the carbs on a motorcycle will be bigger. You cant compare, the motorcycle engines are much more radically ported, and are meant for performance. So yes a bigger carb may help after some mods, but dont go and buy a carb from a 150cc motorcycle and expect it to work well. Hell a carb from a 125 motorcross bike would be too big.

Solder as a crank case stuffer, well personally i wouldn't on an engine i cared about. I really dont know how hot a crank case gets, but it could easily make a big mess if you did manage to get the cases hot enough to melt the solder.

 

[Kenny_McCormic]

Tillotson, don't bother with stuffing.

 

[sloky slocombe]

apparently the length will decide where your engines best revs are i think the longer pipe the higher the rpm. But at revs lower than this it will run like a dog. and higher than that the same. Why not just leave the standard exhaust on it. ?

 

[justin86]

Why not just leave the standard exhaust on it. ?

Many reasons, I know I can make more power with this motor, but I don't want to go all the way with an expancion chamber, since it won't fit in with the look of the kart,
the standard exaust looks boring, and I like to make stuff, this gives me another reason.

I have actualy found the math necissary to design one, just wondering what to do about the porting with this motor now, since it is piston ported. As for the carb I will go with a Walbro wga 1-10. I am getting the manifold cast soon