G1 Air Cleaner

[h040385]

I am working on a yamaha G1. When i got the cart the air cleaner and case
is removed. As it stand the carb is wide open to the atmoshpere. My plan is to use a KN cone filter and hose clamp it to the carb. Any thoughts?

[TheNewGuy]

Welcome to BGW!

Should work, you may have to richen the carb.

[tlwilson5]

you may have to rejet the carb because of the air flow restriction

[h040385]

Thanks for the quick responses. I am also going to perfrom a muffler bbq( video and before and after weight to follow shortly)

[kcnaz]

Originally Posted by tlwilson5

you may have to rejet the carb because of the air flow restriction

Help me understand this......You say the k&n filter is more restrictive. That being said then the Yama filter must be less restrictive because of its size? Or it is less restrictive or inefficient allowing more containments by, correct?

[GMB74]

The K&N filter is less restrictive than the original filter setup. This will make the engine run lean, so you will probably have to rejet the carb for more fuel (make it run richer). Be careful here, running a 2-stroke engine lean makes them run hot and can lead to piston scoring and seizing.

[1989Marathon]

The stock air filter isn't the bottleneck. The 16mm venturi in the carb is. The stock air filter will supply all the air the motor can pull through the carb. Changing to a K&N or UNI filter will have zero affect on air flow. Ask me how I know this...

Modified Yamaha G1 Engine

Modified Yamaha G1 Engine

[h040385]

The purpose of using the k&n filter would be that when I got the cart it is missing the entire air cleaner setup. However that video I found a few days ago and it gave me the idea to just use a universal filter to solve my missing piece.

[GMB74]

Using a K&N filter is a good solution to your problem- BUT- I caution you to read your sparkplug to be sure the engine is not running leaner due to better airflow.
The original carburetor is intentionally small for fuel economy. The engine in 1989Marathon's video has a larger carburetor on it to supply a larger volume of fuel/air mixture for more power. It doesn't matter what you are using for a carb, it still has to be adjusted to provide the proper fuel/air ratio. Too rich and the engine can't burn all the fuel and floods out. Too lean and it runs too hot and burns down. Changing your air filter changes the amount of air coming into your engine, and the fuel must be adjusted to keep the proper balance.

What is that carb in the video? Looks like a Keihin off a snowmobile?

[1989Marathon]

Originally Posted by GMB74

Changing your air filter changes the amount of air coming into your engine, and the fuel must be adjusted to keep the proper balance.

This is a very common mis-conception.
Unless it is clogged or designed to be restrictive(which it isn't), changing the air filter WILL NOT change the amount of air going into the engine. It WILL change the amount of available air. The carb changes the amount of air going into the engine. If the air filter system was designed to control the amount of air entering the engine, it would have a throttle on it.

GMB, the carb in the video is a 34mm Mikuni butterfly carb off of an old Yamaha sled.