Compression release

[StarTech]

Compression Release is accomplished on the INTAKE valve on all B&S engines except Vanguard V Twins. That engine utilizes an,"Easy Spin" cam grind for compression release, no moving parts. The Intake valve finishes closing very late into the compression stroke, IF not, then the Intake Cam lobe is worn off.

Walt Conner

Hmmm. I must seeing things then as I have seen Briggs where it is on the exhaust.

Would like to know the model number of that engine unless Vanguard V Twin, even the Vanguard single uses the Intake Valve for compression release.

Well the old Cast iron engine did use the Exhaust for compression release.

By the way, the original Service Manual did say to adjust at TDC but this was quickly amended by a Service Bulletin which I have on file.

Walt Conner

Here's one that I am rebuilding right now. 216315-0115-B1 SN (Date Code) 090327YD

[Walt 2002]

I do not find an IPL for that model but the next closest shows this to be a typical Intek OHV engine which do typically use the Intake for compression release and the IPL I did find shows the release to be on the Intake Valve. The Exhaust is the top valve and the Intake the bottom one with the compression release next to the cam gear, the Intake lobe.

Walt Conner

[StarTech]

Walt, Apparently you didn't look very well. here is a sources of the IPL.
http://www.partstree.com/parts/?lc=Enter+brand+here&mn=216315-0115-B1
http://www.jackssmallengines.com/Jacks-Parts-Lookup/Manufacturer/briggs-stratton/103231

As the engine sits in normal operating position, The exhaust valve and port is on the left side of the head. In the picture it is reversed as your are looking at the inside of the head. The oil pan (crankcase access(PTO)) is on the left as you look at the cylinder head.The cast iron flywheel is on the right side. The camshaft lobe next the gear with decompression release operates this valve so it is the exhaust. I have gone out and double check this. I even traced the exhaust port back to the valve.

Now is some pictures. Sorry the engine hasn't gone though the final cleaning as I had to OS cylinder and I wait until that is done before cleaning everything spotless. Due to damage to cylinder I wasn't sure it was going to be savable. It didn't cleanup until the last .003.

If you don't see that it is the exhaust that decompresses on this engine then the only way for you to see it get one and see for yourself.

[andybcumming112]

My intake valve is on top manual said it is aluminum.I checked with magnet. But I never seen it bump like was suppose too. Maybe I just didn't see it. I was looking for it to bump on intake. Didn't check exhaust. Anyways mine is running so I guess decompressor is working.

[StarTech]

My intake valve is on top manual said it is aluminum.I checked with magnet. But I never seen it bump like was suppose too. Maybe I just didn't see it. I was looking for it to bump on intake. Didn't check exhaust. Anyways mine is running so I guess decompressor is working.

Andy, If after adjusting the valves as specified and it is now starting better than most likely it is okay. And glad to hear that you got it working.

I am just trying to explain to Walt that not all these Briggs engines have intake decompression; there are some that use the exhaust. I maybe trying to get through a brick wall with a rubber hammer.

[andybcumming112]

Starfire when you get the chance can you get a better pic of that bump. Never seen one. Only seen the ones you replace seperate part.

[StarTech]

Andy, here you go. Note that the spring is barely visible, it is that thin. It is what I would call a hair spring. Got to be very carefully cleaning this area or you might think is just trash. I used a 1/4 extension to hold the decompressor in a position so it would be more visible. The tab to right of the center shaft is what bumps the valve lifter. IN normal rest position it would be up against the bottom of the cam lobe with tip sticking out just enough to bump the valve lifter.

[andybcumming112]

Thanks for pic. Now I see how maybe over time how that tab could wear off.

[StarTech]

Thanks for pic. Now I see how maybe over time how that tab could wear off.

Yes, but the thing is not all decompressers design alike some are a pin with ground flat on one side so as pin rotates comes out play. And then there are the cams with a permanent bump ground on cam lobe. In all case they can wear down to a point where they no longer effective.

The cam decompressers that are spring loaded sometimes lose their springs. Honda cams are a good example of this and Honda can have mean kickback when they fail. The first time I dealt with a bad Honda cam I end up with a badly sprained wrist. The one I pictured petty well works without the spring. It is there just to make sure the counter-weight does go back to rest position.

[GoatDriver]

There can be worn cam lobe problems too....just saying....this one is from an Intek 310000 series