What does Jetting and Porting mean?

[thegoodkidwhomightlikebanshees]

Could someone please explain what jetting means and porting

 

Thanks

[2003LimitedBanshee]

Jetting refers to the appropriate tuning of the carburetor. That is setting the appropriate sized pilot jet, needle, and main jet, to get the ideal fuel/air mixture. You should check out the forum pinned at the top of the jetting page, gives a very in-depth explanation of how jetting works, rather than repeating it here. Porting refers to the process of opening up the intake tracts, transfer ports etc. Basically the means by which air/fuel is introduced, transferred and exhausted from the engine. By porting you are seeking to increase the engines ability to complete this process more efficiently, leading to more power. Porting can also refer to changing the port timing, the time at which intake and/or exhaust begins/ends. However, guys like rocketboy, or PassionRE, and many others would be much more knowledgeable about this than me.

[1sreamin350]

 

What he said.

[thegoodkidwhomightlikebanshees]

Jetting refers to the appropriate tuning of the carburetor.  That is setting the appropriate sized pilot jet, needle, and main jet, to get the ideal fuel/air mixture.  You should check out the forum pinned at the top of the jetting page, gives a very in-depth explanation of how jetting works, rather than repeating it here.  Porting refers to the process of opening up the intake tracts, transfer ports etc.  Basically the means by which air/fuel is introduced, transferred and exhausted from the engine.  By porting you are seeking to increase the engines ability to complete this process more efficiently, leading to more power. Porting can also refer to changing the port timing, the time at which intake and/or exhaust begins/ends.  However, guys like rocketboy, or PassionRE, and many others would be much more knowledgeable about this than me.

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Ok I think now I understand what jetting is, it is to open the carburator and take out the stock needle and put another needle.

 

Thanks really.

However, I did not understand porting. Where is the intake tracts, transfer ports?

[korndawg]

Ok I think now I understand what jetting is, it is to open the carburator and take out the stock needle and put another needle

 

Actually, when you're jetting a carb, you're not changing the needle out for another needle, but just changing the needle position. You will however be taking out and changing your main jet, and possibly your pilot jet.

[2003LimitedBanshee]

Well kind of... You will usually be adjusting the position of the needle, to either richen or lean your midrange circuit. However, some/many, including myself will also change out the stock needle, for an aftermarket needle that has a different profile (generally longer with a more progressive taper), to allow for different tunability. And yes, a fair amount of time is spent adjusting the size of the main jet (3/4-WOT) and the pilot jet (idle-1/4), and the needle so that all RPM/throttle positions provide the engine with the ideal air/fuel ratio (Stoichiometric ratio) in a perfect world 14.7:1 at sea level with 60 degree ambient temp if I remember right.

 

Re: Porting The intake tracts are the intake "runners" that lie behind the reeds. This is the cast portion of the jug that actually leads to the cylinder. Air and fuel travel from the carb, through the reeds, and down the intake tract to get to the cylinder for combustion. By opening (ie. enlarging) these runners you increase the volume of air/fuel the passage can flow to the cylinder. Essentially, the more air/fuel you can get into the same space the more power you will make. But you also have to be able to get it out. This is why the exhaust is also generally enlarged, to compensate for the extra fuel that must now be cleared from the cylinder. Transfer ports refer to ports that allow air/fuel to move from the intake tract to the bottom end of the engine. I believe the theory is because the crankcase is pressured in a two stroke, how efficiently the crankcase (bottom end) can exchange air will affect power, but my memory is a little fuzzy right now.

Edited November 8, 2005 by 2003LimitedBanshee

[race-a-holic]

There's a hole on one side of the cylinder(where the pipe goes),and one on the other side (where the reeds,intakes,carbs go).Inside these holes are smaller holes.When porting,they modify these smaller holes.How's that?