Posting this in the General section as I think some are also using RC carbs on two strokes and this might shed a little light on why it isn't a good idea even for a two stroke.
A little while back I received an email asking me to explain why I don't like the idea of using an RC carb to set a 4 strokes RPM. Not only do I feel the RC Carbs barrel provides a variable air leak, this started me thinking about why it really doesn't work. .
I created a couple quick drawings to show what I believe is the major shortcomings of using an RC carb.
The first image shows an RC carb set for approximately 1/2 throttle. I see two items that will reduce the engines ability to draw fuel. 1. The fuel feed is feeding in an area that is actually larger than the effective choke area. 2. The idle needle actually starts restricting the fuel inlet as the throttle is closed.
Second image represents a carb with a choke screw modification. Fuel feed is exactly at the most restricted area of the intake air path and is not restricted by the idle needle.
I'm not an expert and may not be explaining this scientifically but have a pretty good idea that having the fuel feed located at the most restricted area in the air flow will increase the ability of the passing air to draw fuel.
4 strokes really need to grab a large a gulp of fuel on the intake stroke and in my opinion using an RC carb handicaps the engines ability to do exactly that.
Topic: RC Carb verses Modified Carb (Read 1059 times)