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Engines 101

Michael Lacey I am curious as I attempt to learn more about the 4 stroke engine. I understand the 4 strokes and am most curious about the 1st - intake.

Gas and air mix in the carburator and enter the valves and bores in the form of a gas via atmospheric pressure - is this correct? I understand no suction is involved.

My question is, what causes your engine to increase rpms? are you essentially forcing more gas and air mixture into the engine, essentially providing more to burn and push the pistons at a faster rate?

If this is true, what would cause a delay in throttle response? Meaning, when i increase throttle the rpms do not instantly increase. There is a few second delay and it is worse when the engine is not warmed up (which seems to take a good 5 - 10 minutes).

Could anyone share their knowledge?

Bob G Fuel and air mixture is "sucked into the cylinder". As the piston goes down with the intake valve open it pulls in the mixture, or you create a low pressure area and the atmosphere pressure pushes it in. All the same to me.
When you open the throttle, the air mass thru the venturi increases which pulls more fuel into the mixture, more fuel equals more combustion pressure and the piston is driven down faster.
I would check for loose linkage in the throttle system and adjustment of the governor. there is a cause and effect delay in it tho. You just have to figure out what is normal.
hope this helps.

Jim Loveridge That lag time in throttle response isn't right. My '54 responds right away to changes in throttle position. Have you ever done a compression check on yours? It sounds more and more to me like your engine is really tired.
johnb I would think a minor time lag is caused by the inertia of the moving engine parts.
Bob G It is amazing how small of a movement of the throttle plate will affect the RPMs in these engines. The real test is to remove the linkage from the throttle plate and move it by hand.
Michael Lacey I have never tried a compression check - on my list to do. I am almost afraid to find out what it is...in due time. I noticed some slack in the throttle linkage, but onces its warmed up, its much better, but again, not perfect.

I'll be sure to try it by hand next time, great idea!




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