Using a leak down detector

[bluemoon11]

I have a Briggs (123K02 0243 E1, Troy Bilt trash day find lawn mower, 2003). I have a OTC 5609 Leak Down Detector. I'm getting 16% leak down with most in not all air coming out the oil fill tube. The compression was about 50 - 55 psi. The carb needs to be rebuilt. I got the engine running for a while and it seemed unpowered. So, is 16% OK for a 12 year Briggs? For a car engine, 16% is bad. I've never used a Briggs leak down tester. On YTube, it seems you get green or red, no percentage when using the Briggs tester. Any comments?

 

[ILENGINE]

When you say 16% do you mean that you are getting 16% bypass and therefore holding 84% in then good or green. Or do you mean that the gauge is reading 16% and have 84% bypass, meaning most of the air is escaping past the rings.

 

[bluemoon11]

I was getting about 16% leakage, 84% holding. The OTC chart only goes to 15%. At 100 PSI source, the leak down gauge reads about 82 - 83 PSI (85 PSI is 15% leakage according to the chart). So I am guessing the leakage for the engine is 16 - 18%.

 

[ILENGINE]

Some air leaking past the rings is normal If the cylinder is holding around 85 psi I would consider it good to go. This is were the leak down tester comes in handy, because you were only getting like 55 psi with the compression gauge, which means it has compression release.

 

[bluemoon11]

The Illustrated Parts List for the engine show a compression release. When I slowly rotated the engine looking directly at the exhaust valve through the spark plug hole, there was no "bump" with the valve. So I assumed there was no compression release and 55 PSI to be a "bad" reading. Is this engine worth $15 for the carb rebuilt kit? With a weak engine, I would say no. Another $10 for a head gasket, should I pull the head? Lap the valves? See if a broken ring has damaged the cylinder wall.

 

[bertsmobile1]

If it is a 2003 model the decompression is most likely on the inlet not the exhaust.
It got moved due to the EPA Nazis protecting us all from having children with 6 arms cause by all those toxic unburned hydrocarbons escaping out of the cylinder during starting.

One the B & S guru's could probably put a serial number on it but it looks to be around 2000 ish.

 

[bluemoon11]

I was told the compression release was moved from the intake to the exhaust valve because the "bumped" intake valve made the engine hard to start when hot.

 

[bertsmobile1]

I was told the compression release was moved from the intake to the exhaust valve because the "bumped" intake valve made the engine hard to start when hot.

Yes it does.
But just like the fuel cut off solenoid, the inlet valve decompressor is to satisfy the EPA shinny bums who live in apartments.

 

[bluemoon11]

Just did a leak down test on my 2000 Craftsman 6HP Briggs (Model: 12H802). 99% holding, 1% bypass (or leaking). This was with vise grips holding the flywheel cooling fin against the magneto just past TDC with the engine cold. Held flywheel against the magneto with the next cooling fin and got the same reading. Not going to do any more compression checks on lawn mower engines.

I'm going to assume with a 16% bypass on a 13 year old engine is not worth investing money.

 

[Mikel1]

I have the otc leak down tester, works well.