RCPAUL

My Feedback: (1)

I do not have any YS engines.

However, I was recently told that the regulator on the engine regulates fuel volumn and not fuel pressure. Is this correct? I always understood the reverse.

RCPAUL

w8ye

My Feedback: (16)

The regulator is probably both. It depends on how you want to look at it. It is controlled by the positive and negative impulses of the crankcase volume. So therefore, as the engine speeds up or slows down, the regulator will allow more or less fuel to the carb. Being as the diaphragm is a spring biased rubber flexible type device, There is some pressure control based on the tension presented by the spring and the adjusting screw which should be flush with the case on the engines with a low speed idle air bleed.

Enjoy,

Jim

JWN

My Feedback: (42)

The best place to check would be the YSPerformance direct support forum. Dave Shadel could answer the without hesitation. Keep in mind that you will need to ask the question either towards the 1.40DX or excluding it since that engine uses a true fuel pump and not a pressure pump/regulator as all other YS's do and it's operation is different.

John

djlyon

Most accurately it's called a pressure reducer. It's adjustable to control the mid range mixture. The pressure pump is the piston and crankcase. It will put the same amount of pressure in your tank whether its running at 100rpm or 10000rpm (slight leakage rate excluded). Only the time to reach full pressure will change. Once pressure is reached you only need enough rpm to produce the gase volume necessary to replace the fuel volume lost.
I call it a reducer because if the input is 8lbs and the out put is adjusted to 4lbs and the input drops to 6 the out put will drop to 3. That's reducing not regulating.

djlyon

Actually RCPAUL, whoever told you it controlled fuel volume was correct in the sense that the system is for practical purposes a constant pressure system and as a result the fuel flow rate is controlled by engine rpm and regulator/reducer spring pressure. The fuel valve , in the regulator, opens once every firing stroke allowing fuel to flow to the carb. Tank pressure is constant , spring pressure is constant and the variable is rpm which controls fuel flow.