Hi Guys, I was wondering if anyone could tell me the correct or at least acceptable compression on a Briggs 2Hp. Engine number is 60102 from a SB45 14inch. I'm currently getting around 50psi.
Hi Towney, Welcome to the forum. 50 psi is a too low for my liking, although i don,t know the exact comp, i like to see 80-90 at a minimum. Before you rush off and strip the engine for a rebuild, i suggest you check the valve clearances(inlet 6 thou, exhaust 8 thou) and lap the valves. Hope this helps.
As Bigted said the compression seem a little low. The actually compression reading is not possible due the decompression system but I use 70 psi as a base line. These engine like most Briggs L-head tend to close the valve clearance over time leading loss of compression as does carbon on the valve seats. So as Bigted suggests check the valve clearances first.
Briggs recommends using leak down testing to find leaks and to determine the cylinder condition. Even it will not find all the problem at times. Now to get a true compression reading you must be able to spin the engine at idle or above speeds at which normally over rides the decompression system.
With doing leak down tests on L-heads it not possible to check the cylinder other than at TDC. What worst is that Briggs says that the leakage rate of up to 40% is acceptable. Personally if it is over 20% I look for problems,
With OHV it is possible to check the rest of the stroke as you can disable the valve train by removing the push rods. A good example of the modified OHV test is one I did back in December where I an oil burner here. It pass the standard leak down test with 10% leakage rate but after I disable the valves and checked BDC it had 60% indicating a severely taper cylinder. Now this modified test is not in the tester manual.
Just something to note with compression testers, when using compression testers like the RYCO one in the image below the black hose and the fitting that screws into the plug hole adds to the combustion chamber volume in the head ,this gives you a false compression reading.The compression reading is 20 PSI lower than what you will read on a short compression tester like the one below with the green scale.
Both compression testers were used on the same mower the Ryco reads 50 psi and the short comp. tester reads 70 psi.
I use 50psi as a minimum reading when using the RYCO gauge.
