HOW THE COMPRESSION RELEASE WORKS ON MOST SMALL ENGINES

what's up guys more medic one here uh today i just want to kind of go over uh some miscommunication and some of the forums that i belong to on facebook uh a lot of guys are saying well my starter spins over and it goes halfway around and locks and there could be several things it could be you could have the uh the carburetors leaking then you actually hydro locking the piston could be the valves out of adjustment and lastly it could be actually a broken uh compression release on the cam shaft now let me show you this thing a little better up close guys don't mind the rust it's just an old one and i've got an old sump here for demonstration purposes i would not reuse this camshaft and anything that i would repair but here would your here's where your crank would come up through with your crank gear right here and it meshes with this cam shaft and this cam shaft spins at half the rpms as the crank does but what happens when this camshaft is it idle not moving the compression release is in its compression release state and as this camshaft starts spinning it slings this flyweight out like yay and let me show you and see how most of the time though it actually will break off the shaft will break off inside the cam here or this very tiny spring gives out and it won't let it you know retract back all right so whenever this thing is cranking over and the flyweight is staying still under i think it has to be like 300 rpms or starting speeds to get this thing to start uh moving and as you can tell when it does move out it clears the camshaft and what this thing does is when it's in this mode right here you can see how that protrudes if it will focus correctly it protrudes up about 30 or 40 thousands and it lifts the valve tap it up just a split second to relieve that compression you can see how much that would actually lift that tepid off of the camshaft just for a split second just enough to relieve the compression inside the combustion chamber and whenever this thing is spinning it basically just has a flat spot and lets it fall below the lobe profile and then the tap it just rides on the cam shaft as normal not all small engines have a compression release built onto the cam shaft on some atvs and some of the japanese engines they'll actually have a lever that you twist on the cylinder head to relieve the compression and like and there are other ways to do it also is on like on a two-stroke uh on a steel chainsaw you'll actually have a decompression valve it actually looks like an engine valve and whenever you press it it unseats till it cranks and it pops back up a pretty neat system very super simple as you can tell this uh lifter here is dished this is for a push rod engine probably like a 17 or a 14 and a half briggs this is this very very old style one of the first camshafts for the 14.5 or the overhead valve briggs engines the single cylinders they've since upgraded this to the skeletonized preston lobe camshaft and this will not interchange this camshaft will not fit the newer sump all righty guys we got the camshaft looked at i know this is a long time coming and hope that cleared up some confusion over there or if this helped you out and you learned something today about decompression valves or decompression uh mechanical releases on camshafts let me know and give me a thumbs up and smash that like button and hit that subscribe if you would would help me out tremendously and while you're there click the bell so you'll get all my new videos alrighty guys we'll see you on the next one have a great day

Channel: THEMOWERMEDIC1

Views: 88,672

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Id: 1uzUf9UkpDQ

Length: 4min 57sec (297 seconds)

Published: Mon Jan 18 2021