How The Compression Release Mechanism Works On Briggs And Stratton OHV Engines




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Joseph Alvord: what if mine isnt a ohv system i have a briggs and stratton 12.5 gold model and it has really high compression any ideas? i've changed the connecting rod and i torque it to what the instructions said and put it all back together and tried starting is when i found out i had high compression the starter is good had it checked out and the starter gear does get stuck on the flywheel 

VintageOutboardMan: Hey man, I've seen this video before, but I got a question. Do you know when Briggs started using these automatic decompressors? I have a 10hp Briggs from 1976 and with my compression tester I got only 60-70PSI out of it. The engine is not burning any oil and it has lots of power! When I turn it slowly by hand, I can feel a lot of resistance too. If it has an automatic decompressor, 60-70PSI would be excellent, so may I assume it has one??? By the way, yes my compression tester works accurate ;)

mowerman45: Thanks!!! thats about the only thing i think could be the problem

Aaron Zepeda: Interesting! My starter had trouble cranking over & it melted abit. The starter stops on the compression stroke. Its spins freely without the spark plugs in. I thought it was the weak battery, rusty coils, bent crankshaft & etc, but never thought about this. Well, I guess I'll rebuild my starter & 25hp b&s intek engine!

Nick'sGarageDoorService: @outdoorsman310 That's a good idea, but the problem is what if it wears too fast? And either way, metal shavings are not welcome/good in any engine. :-)

madisonelectronic: Thanks! Does it work the same in a Honda 13hp? It runs great but starting it breaks my arm. The valves have been set to 5 and seven (I and O) I am gonna check tonight if I see that movement of the intake valve when I turn it by hand. I cannot think something is broken cause the engine (a real Honda) not a knockoff has maybe 20 hours running from new.

fnaguitarplayer9: no problem. i'm not really sure, i've never worked on a honda, worked on a few honda carburetors thats about it. i figure it is something like this, i know some motors have a manual compression release. It should be on the exhaust valve, but in some cases its on the intake. well you never know, it is possible that something broke, i doubt it though being that new. You could try to set the valves a few thousandths less, like 4 and 6, some are picky. hope this helps. thanks for watching!!!

teerification: I have a PowerBuilt 17.5 OHV briggs. Has that hard start/unadjusted valve issue.

myozone: the exact opposite to a jack brake on a truck

teerification: which valve releases the compression? exhaust or intake? plz help

fnaguitarplayer9: heard that, its a very common problem on OHV motors, i showed it one of my videos, if you search for briggs 14.5 ohv on my channel its one of those videos. i can't remember which one it is.

EdoublS: .004 on the valves. Would it be safe to say, the compression release on the cam is the problem?

fnaguitarplayer9: its usually the exhaust valve, but on some engines its the intake. And on some engines (not lawn mower engines) its a separate valve that releases the pressure. thanks for watching!

1899lpv: Sweet !

EdoublS: I have a b&s 16.5 that came to me with the aluminum pushrod been pretty bad coming out the side of the rocker arm. I replaced the pushrod but now it's still hard turning over and I believe that the problem is within the camshaft. when I get to the compression stroke I get a lot of resistance, and I hear a hiss coming back through the carburetor which tells me that the head gasket is bad. I have already adjusted the valves correctly. I do believe that the problem is with the compression release.

old64goat: Good info. Thanks for uploading. Bill

fnaguitarplayer9: thanks for watching!!!

outdoorsman310: they should make that to wear away as your engine looses compression

teerification: Thank you! I have to adjust my valves as soon as I get my feeler gauge I ordered on amazon.

Robert Smith: great video, i see you've done the spring maintanance video, cant wait to check it out

fnaguitarplayer9: No Problem, thanks for watching!!!

fnaguitarplayer9: yeah that would make sense! thanks for watching!!!

fnaguitarplayer9: its uploading right now, be up in a few hours... thanks for watching

fnaguitarplayer9: no problem! i've been meaning to put this video up haha same here.

Guy Garic: thx

fnaguitarplayer9: thanks for watching!!!

fnaguitarplayer9: just about any time one is hard to crank over its in the valves or compression release, most of the time you can adjust it out, but the bump on the cam for the release can wear out or jam up. i would think so. try cranking it without the plug just to make sure you don't have a bad starter. thanks for watching!!!

fnaguitarplayer9: you wouldn't have to rebuild the engine, all you need to do is adjust the valves, if the valve clearance is to much the compression release won't work right or at all depending on how bad. but the starter may need rebuilt since it got so hot Thanks for Watching!!!

James Humphrey: Also, like fnaguitarplayer9 said, before tearing down, try to reset your exhaust valve setting, if it is sloppy and wide, it may adjust out, if it doesn't then you can look for a problem on the cam and that is a tear down.

James Humphrey: A quick way to check to see if the compression release is the problem on a hard to turn over B & S OHV Engine. Take the valve cover off and turn the engine to the position where it is really hard to turn. You need a helper and expect to get a little oil on you. Have your helper, when you tell him to try starting the engine, now take a screwdriver and put the tip onto the valve exhaust valve lifter - on the very end right over the valve stem or on top of the valve spring cap - carefully push in about a tenth of an inch THEN have it turn the key to start. If your engine has had a habit of being easy to start up to now, it will spin, fire and most of the time start. You may have to try this a couple of times at first to get the knack of it as when the engine turns over your screwdriver will bounce off. Be careful to push in just a wee bit, you will probably feel the valve stem give way just a tad, that is all you want to push. They will usually start after one full cycle but if your engine has a lot of miles and a habit of hard starting, you may have to try it a couple of times ?? If this doesn't work, you may have an intake compression release, try that one. When and if it starts the engine will start pumping oil an you will get squirted a little and the oil will also run down onto the exhaust, no problem just turn the switch off. Now if this works you have just identified for sure what the problem is so either take off the bottom case and repair yourself or take it to the shop. Have a nice day. Jim

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