Honda 2-Stroke Engine Questions

[Saint Nick]

Hey guys, recently picked up an '83 Urban Express. It has a 50cc two stroke. I've been going over the bike performing some basic maintenance, and I was wondering, should I probably go over the carburetor?

Only reason I ask is because its got about 3,000 miles on it, the air filter was relatively dirty, and the transmission fluid was black (all mean it has typical wear and tear). But, I'm assuming the previous owners probably didn't perform maintenance like they should.

So should I clean the carb? What is jetting?

 

[franksta]

Definitely clean the carb. Jetting is putting in the correct jets (sorry) for the proper air fuel ratio.

 

[Saint Nick]

Originally posted by: franksta
Definitely clean the carb. Jetting is putting in the correct jets (sorry) for the proper air fuel ratio.

Is that what the needle is for? A "jet" is just the hole in the carb? Or is the "jet" the actual action of fuel and air mixing?

 

[Zenmervolt]

Originally posted by: NightDarker

Originally posted by: franksta
Definitely clean the carb. Jetting is putting in the correct jets (sorry) for the proper air fuel ratio.

Is that what the needle is for? A "jet" is just the hole in the carb? Or is the "jet" the actual action of fuel and air mixing?

The "jet" is the hole through which gasoline is siphoned out by the venturi effect of air passing though the carburetor's venturi chamber (also called the "barrel"). Typically the jet itself is brass and is screwed into a fitting, allowing the (relatively) easy exchanging of jets for different purposes (e.g. high-altitude adjustments).

"Jetting" a carb historically referred to either replacing the stock jets with oversize jets (i.e. jets that allowed more fuel) that, while causing idle problems, helped out for race use, or to physically drilling out the stock jets so that the holes were larger (same effect as replacing the jets with larger ones). These were common modifications during the muscle car era.

Good basic primer on a carb's operation.

More detailed intro, including information about carburetors with multiple jets and about synching multiple carbs.

A good list of general points to keep in mind when adjusting a carb.

ZV