Is there a way to measure how rich or lean a bike is? I read (on the internet so it's true) that removing a catalytic converter actually makes the bike run richer and would like to test that theory out. I don't need a tune, just wanted to see how rich/lean the bike is before and after the mod. Other than a state inspection place (and they can't just hook them up and check) I don't know what I can do. Is there any device that would allow me to check this other than sticking my nose in the exhaust and smelling. I guess if it goes any leaner I would see the pipes turn but how about richer?

 

Us old timers used a very simple trick:

Ride wide open, close the throttle. If the bike coughs, you are running rich.

Ride wide open, close the throttle. If the bike speeds up slightly before slowing down, you are running lean.

The above is a test only for the main jet on a carbed bike.

 

The cat is after the fact so to speak so it should have no affect on combustion mixture. What very slight amount of restriction a cat causes, when eliminated theoretically could make it go slightly leaner, but the O2 sensors would shift the mixture back where it was.

 

Best way to do it is with an EGA (Exhaust gas analyzer)

Takes all the guesswork out of it.

 

I doubt what you read is true but if you have a DVOM you can measure your O2 sensor voltage. If it reads continuously above 750 MV you are running rich.

 

I would say that the cat do have some affect on combustion mixture. Removing cat decreases back pressure somewhat. A combustion engine is designed and tuned to run with a certain amount of back pressure.

 

Been a long time since I used one. A 2 gas analyzer required a port upstream of the cat for an accurate reading. I think they were moving to 4 gas units when I got out of the business. We had started measuring the milivolt reading off the o2 sensor with it unplugged. They will generate a voltage reading in proportion to how rich or lean after they warm up. Higher voltage means richer mixture.

 

Back in the late 60's, we would check the condition of the spark plug to see if the engine was running lean or rich(and burning oil). If the spark plug's ceramic insulator was black, the engine is running rich; if white, the engine is running lean. If light brown and clean you are good.

 

Back in the day, your nose could tell if it was rich or lean. Hydrocarbons (rich) and nitrogen oxides (lean) have distinctive odors. Black smoke is also rich.

 

I think the ecu keeps it in a tight enough range that smelling might not work. As far as measuring voltage, that would work if I had any idea what I was doing. I wonder if I could rent a gas analyzer.