building second build need some input on port matching

[wan37]

I just put my first bike together in may 2011 and it went well.Now working on second build I got lucky I put first bike together from right out of box.So now I now more about them and read theses forms Is the port matching something I really should do on fresh build just don't want to get junk in motor and tell me the best way of doing it.

 

[bideronit13]

Welcome,
Exhaust and carb work go hand in hand. A ratio of exhaust to intake should be 80% to 85% meaning that the exhaust is 15 to 20 % smaller then the intake for perfect tunning. It might not be perfect unless your exhaust is correct.
For instance I purchased a pipe from bicycle-engines and had poor performance from it. I took it apart and rebuilt it and anticipate perfect tunning.
I've attached a picture so you see I'm not spinning your wheels.

 

[blue 48]

@ bideronit13 what have you done there?

 

[blue 48]

i done the piston file trick someone told me about and with std carb and stock exhaust it goes quiet well i think.

 

[bideronit13]

I rebuilt my exhaust pipe. I attached a sketch of more or less the new exhaust.
On a regular exhaust the seals are not entirely sealed. On my exhaust they are sealed with JB weld and skoal can tops.
Without a proper seal the exhaust cant be directed evenly. Instead its uneven causing uneven RPM's.
Also with the use of the fiberglass packing makes it even more even and directs it in a precise flow causing more back pressure and an even RPM.

 

[HeadSmess]

awesome exhaust dude. im impressed. totally

bet it goes like a cracker too...

anyways. i never bought a pipe from anyone.

i made one instead.







and that file trick that 48 mentions... combined with this pipe?

cough cough, ahem...

yeah yeah, i went back to the stock nt carb too...

 

[HeadSmess]

and im not sure, maybe i grew up in a tin shed...but im fairly sure that the exhaust port should be LARGER than the inlet? what with exhaust gas being hot and expanding and occupying more volume and needing to get the bejesus out of there?

anyways...

port matching.

hardest part is marking them out so you know where to file... usually use liquid paper myself... theres that file trick. involves pulling the cylinder and piston off. getting exotic.

ive always felt it best to replace the wrist pin clips if i touch them at all. every time i reuse them i curse myself afterwards as i push home... and you need a set of gaskets on-hand. they never come off clean unless you have a spare!

basically all there is to do is in the intake. and most of that in the manifold which you can pull off the engine and do in the bench vice.

anything else ends up being more work than its worth

 

[blue 48]

oh thats right you told me sorry bout that it worked a treat by the way. i did it while it was appart for ummmmm maintenance (removing broken ring) so new gaskets were on the cards any way 400km later its still going well