Nibbi Carburetor Choke Open Or Closed Position?

This question seems to also stem from, is my choke on or off on my Nibbi Carburetor, and How do I turn on the choke on my Nibbi Carburetor? So the plan is to cover this FAQ in one post, answering, What is the Nibbi carburetor choke is open or closed position?

Just A Quick Summary Why You “Choke” An Engine.

Just a basic summary of what a choke is and why you use it on a motorcycle, or any internal combustion engine.

What Is The Choke Used For On A Motorcycle?

When an engine is cold, or when the outside temp is really cold, there is a delay in the vaporization of gasoline. The fuel going through the carburetor isn’t vaporizing very well before it enters the motorcycle cylinder(s).

This condition leads to the engine running very lean(too much air/too little vaporized fuel), without enough fuel to even start the combustion process properly.

How Does A Choke Work On A Motorcycle?

Since you can’t increase the fuel’s vaporization, to re-balance the fuel/air ratio, carburetors are designed to have the ability to reduce the air amount in the engine. Usually, this device is a select-able air restriction device (usually a single-purpose butterfly valve) upstream of the throttle body of the carburetor.

This “Choking off airflow” re-balances the fuel/air ratio to ensure proper running of the engine during cold starts.

How Is The Nibbi Carburetor Different and Sometimes Confusing?

The rebalancing of fuel/air ratios with an air restriction device, like a butterfly valve, is accomplished by ‘choking’ the airflow through the carburetor. So… this rebalancing and restriction of airflow(“choke”) have been used intermittently over the years, to the point that now we only say “choke.”

How Does A Nibbi Choke Work On A Motorcycle.

Now where this Nibbi carburetor comes in different or confusing, it doesn’t accomplish the rebalancing of fuel/air ratios by restricting airflow but increasing fuel flow into the motorcycle engine cylinder(s).

This Nibbi Carburetor Has A Fuel Enrichment Circuit Choke.

So when you look at this Nibbi carburetor, you don’t see an airflow restricting plate/valve upstream of the throttle slide; you see no restriction device.

Where the ‘choke’ operation occurs is a tiny port that opens and closes with the “choke” on or off. A single plunger operates all on the engine side of the carburetor.

Why Is The Nibbi Choke Plunger Missed?

From what I read, the choke plunger spins.

Some people believe since the plunger top is round and freely spins, the knob for turning/twisting, not pulling or pushing.

Now that is covered, here is the simple operation of the Nibbi choke plunger.

The Nibbi Choke In The On Position.

Pull up on the Nibbi Choke Plunger to it ‘clicks’ into position for the choke to be on. The plunger should stay up, and you now have the Nibbi choke engaged. This step opens up the extra pathway for fuel, the enrichment circuit, increasing the fuel/air ratio.

The Nibbi Choke In The Off Position.

After using the Nibbi carburetor choke feature, you push down the Nibbi Choke Plunger to its original position. This step closes off the extra pathway for fuel, the enrichment circuit, returning the fuel/air ratio to normal operating levels.

Now the Nibbi carburetor has the choke off for the regular engine operation.

Hope this helps, and if you would like you can real more about the Nibbi carburetor I picked up here: Nibbi Carb vs. TBR7 Stock Carb.

Additional carburetor reading sources: https://en.wikipedia.org/wiki/Carburetor#Choke

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