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




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99trider: All is well now. I do not know exactly what got the kinks out but the engine is running fine now. At my last posting the engine was surging when under load, tried new fuel pump.. no help, removed the the new in-line fuel filter...no help. Finally removed the carb, poked, probed and cleaned. Never saw anything in the carb that would prevent fuel flow??? Replaced old crankcase vent tube that had a hole in it, but the carb back on and now it runs fine?? I did not  rebuild the carb, did not put any new parts in the carb, no gaskets, no needle, no anything new.
Thanks again for all your help!

99trider: Finally got the new camshaft in, the mower starts and idles fine but surges/lopes when I start mowing. Is it possible I installed the governor wrong 

99trider: Thanks again for your help. I had B&S send me a parts manual and they also list my camshaft a the 790340...I hope this is correct as I have ordered one. I will post my results here once I have the engine back together.

Franklin Jobe: Thanks for your reply. Please confirm the correct part number,  best I can research it is part # 790340.
Model  311-777
Type    0154-E1
Code   000317ZE

99trider: I have a 17hp B&S OHV with the exact cam you show in this video. I adjusted the valves but still could not get the engine to spin over unless I removed the spark plug and yes I tried with a strong, fully charged battery. I have the engine opened up now as I intended to replace the cam thinking the problem is the compression release. Now that I have the cam in my hand I cannot tell if it is the problem, the mechanical release is not broken and it seems to operate as designed. Is there any way to tell if its worn too much to work properly? Do these type releases ever just wear out? I think this engine is about 15years old.
Thanks

Ro Efa: I replaced the head gasket on my engine, and that small cap on the end of one of the valves stems found its way to the crankcase and it broke both the counterbalance link and that centrifugal doo-dad on the cam gear. I have a new link, but Briggs won't sell me the spring and weight assembly... only an entire new camshaft w/gear and weight... too expensive. Do you know of a practical way to add a manual compression release? Some motorcycles have them. PS: Really enjoy your videos; THANKS.

kenny sylvia:
hey I have the 5.5 black model   its a walk behind as well I just had everything apart put together  and working fine  after a few  pulls it locks up do u have any idea that may help me please and have a happy fourth

Nickolas Davies: ah yes finaly, been fixing a tohatsu 4 stroke efi 25hp that suffered a swim, got it runnig all good but could not figure out why it took such a massive amount of force to pull.
then saw this video and all made sense, all 3 were jammed full open so no decompression prior to start.

thanks for the upload.

EASTYJAZ34: My Quantum engine is experiencing Knocking sounds when i shut the engine off. I have made a video about it. What do u think the problem is?

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

Joseph “67FordFalconLover” 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 ;)

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.

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

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

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!

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

fnaguitarplayer9: No Problem, thanks for watching!!!

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