Hi, typically what is the compression of a 6.5 hp briggs engine? I checked mine and it was reading 30psi. It starts hard, but seems to run ok once started. I didnt think 30psi was even enough to start it. This engine,after priming 6 or 7 times, kinda chugs then dies a few times before it runs normally..any thoughts??
Hard starting
- Thread starter Jeff P51
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First it would be nice if you would post all numbers, you’re missing the code number so we don’t know how old this engine is. Yes, 30 psi is low, but there are many things that can contribute to this. Bad head gasket, compression release problems, valves sticking, bad rings, etc. From your description I wouldn’t jump to a compression problem. If it runs fine once started I would be looking for a different cause. When you prime the unit, have you looked into the carb throat to see if fuel is actually entering the air horn each time you push the primer? You just have a bad filter base to carb gasket.
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First if you known it was a head gasket why did you bother posting other than to harass someone.
As for the compression reading it depend on your gauge set as automobile compression testers usually reads lower due the stiffness of the check valve spring and hose length.
But it would not hurt to check the valve clearances while you are at it. L-Head (side valve) engines tends to close up the clearances leading to a lost of compression. Plus with an ACR which this engine camshaft has, once it starts the compression climbs closer to normal operating pressures.
Btw the date code is important as Briggs does make changes through the year; not just at beginning of a particular year so your part numbers can be different based on when they made the engineering changes.
Personally I get tired of people acting it is a crime to give us the info we to help someone... They act they have stolen equipment and afraid they are going to get caught.
As for the compression reading it depend on your gauge set as automobile compression testers usually reads lower due the stiffness of the check valve spring and hose length.
But it would not hurt to check the valve clearances while you are at it. L-Head (side valve) engines tends to close up the clearances leading to a lost of compression. Plus with an ACR which this engine camshaft has, once it starts the compression climbs closer to normal operating pressures.
| Intake Valve | .005-.007 in (.13-.18 mm) |
| Exhaust Valve | .007-.009 in (.18-.23 mm) |
Btw the date code is important as Briggs does make changes through the year; not just at beginning of a particular year so your part numbers can be different based on when they made the engineering changes.
Personally I get tired of people acting it is a crime to give us the info we to help someone... They act they have stolen equipment and afraid they are going to get caught.
Wow...I didn't know it was head gasket when I posted it. While waiting for a response , I hooked air up to block and found it leaking. Personally I dont appreciate your attitude. Then another guy says dont jump to conclusion that its a compression problem. Its got 30 psi...I think its a compression problem..
Also it was a general question what is the TYPICAL compression of a Briggs 6.5..not really a question requiring a model number..which btw was never answered
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With an ACR present normally it should be at least 70 psi but a compression test on ACR engines is usually useless due the ACR action. This why Briggs and others engine manufactures say to check cylinder condition you should do a leak down test. And there is a modified version of this test that can be use on OHV engines as the base test only checks the upper cylinder where the modified test on a ohv engine can check all levels of the cylinder. It requires disabling the valve train which you can not do on a L-head engine.
Again we had to know the engine as some didn't have an ACR
Again we had to know the engine as some didn't have an ACR