5hp Briggs has 20# compression

B

ba_50

Well-Known Member
I replaced the head gasket and nothing changed. It was running but getting harder to start than wouldn't do it at all.
There doesn't seem to be any gasket between the cylinder head and base. So what does that leave? I cleaned the valve seats and top of piston. There is no scoring in the cylinder. This motor is on a tiller.

Are these motors only supposed to last a couple of years?

Thanks for any advice.
 
Lets starts with a model type and code off of the engine so we can see what you are looking at. 20 psi is very low, there is suppose to be a gasket between the head and the block. Most are a graphite type material, but the older ones where metal.
 
primerbulb120 said:
Your compression tester may be inaccurate. Make sure it is for small engines and not for cars.
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What is different? I have two compression testers and have used them for many years on anything with a gas engine from a scooter to a large truck and they have always told me what I wanted to know. Not that I am arguing here just curious? because you must have a reason.
 
I have a Harbor Freight car compression tester that gives me inaccurate (low) compression readings on small engines. I figured that the tester needs the larger displacement of a car engine to work correctly. The larger the engine, the larger the compression reading. A leaf blower gets no more than 60 psi, while my 9 HP ATV gets 120 psi. It could be that my compression tester is just low quality, but I think that you should use a tester made for small engines when testing small engines if you want accurate readings.
 
primerbulb120 said:
I have a Harbor Freight car compression tester that gives me inaccurate (low) compression readings on small engines. I figured that the tester needs the larger displacement of a car engine to work correctly. The larger the engine, the larger the compression reading. A leaf blower gets no more than 60 psi, while my 9 HP ATV gets 120 psi. It could be that my compression tester is just low quality, but I think that you should use a tester made for small engines when testing small engines if you want accurate readings.
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First of all my tester is top of the line Snap-On. Just never looked for a different compress tester because never felt a need to. What you are saying dose make sense. but never came across a tester for small engines only compression tester, not saying there isn't such a thing because I haven't looked. I said I have two tester and the other one is just a real old antique off name tester I picked up at a flee market and both tester read the same.
 
I don't have the numbers with me right now.

I tried the tester in an Evinrude 8hp motor and it was about 95# so it works.

Can't remember where I got it or who made it but it is probably a cheap one.

I'll get back with you tomorrow.
 
ba_50 said:
I replaced the head gasket and nothing changed. It was running but getting harder to start than wouldn't do it at all.
There doesn't seem to be any gasket between the cylinder head and base. So what does that leave? I cleaned the valve seats and top of piston. There is no scoring in the cylinder. This motor is on a tiller.

Are these motors only supposed to last a couple of years?

Thanks for any advice.
Click to expand...

How did you clean the valve seats?
 
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