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I purchased a JD mower with what I expect is a junk motor. (26 hp v twin)It has absolutely no compression at all. I'll post model n type tomorrow. Crank isn't broke what would the suspect be ,cam ?

RDA.Lawns said:

I purchased a JD mower with what I expect is a junk motor. (26 hp v twin)It has absolutely no compression at all. I'll post model n type tomorrow. Crank isn't broke what would the suspect be ,cam ?

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I don't mean this in a bad way but making those kind of statements leads to where it won't be long before some overzealous young mechanic (or a dealer looking to make a fast buck) telling you that you need a whole new engine. And again I don't mean to scare you but usually they're over a thousand dollars in that horsepower range with the two cylinders, plus labor it can get pricey quick... Please be more careful before self-diagnosing the worst-case scenarios or you'll be forking out unnecessary cash some days.

I mean how do we come up with a zero compression scenario...

I wouldn't even try to start an engine the history of which I am uncertain of.
First thing to do is check the oil, if that needs changing I likely would do so even on a cold engine, even if it needs it again later.

Then you need to see if the spark plugs are in there...
If they're missing you won't get compression, but you should pull them anyhow and spray some wd-40 in there to give the cylinders some initial lubrication.
Once you pull them, check their gap is .030 and then make sure they're snugged up.
At this point I would probably try and start it once, just to see if it will fire.
If it doesn't then you need a compression gauge with which to measure, and you have to be absolutely certain you're getting a good seal.

Never assume the worst, always start with the simplest.

Wow ok first off I'm not someone who knows nothing . Sorry for being blunt about that. It has zero compression on both cylinders . I think. My gage starts at 15 lbs. I've not tore it down not sure I will. Just fishing for opinions right now. It seems odd that I'd have zero on both cylinders . But I'm sure the crank isn't broke .

B&S engines have compression release bumps on the camshaft lobes, so at normal cranking speed it can fool most any compression gauge. (it fooled my compression gauge).
This is done to make the starter have an easier life. Then once started & running higher RPM's compression is restored, then the release bumps are never even noticed in power.

And when setting valve lash on B&S engines, one must find TDC for one cylinder, then rotate engine 1/4" past TDC to get off the C/R bump in cam. Then precise valve lash setting can be accomplished in that cylinder, then repeat procedure.

I've kinda been raised around B&S engines. & my last 2 tractors both had B&S power.

I can turn the motor by hand from the flywheel with very little effort. Its also low on oil. Purchased it from my cousin. He said it was running and died with no loud noises at all. I have very little intentions of tearing it down at this point. I may pull valve covers see if the rockers are moving at all .

Checking for rocker movement would be a good start. The cam in some of the Briggs engines are made entirely out of nylon. And some (I think smaller ones) they even used plastic camshafts.

You could squirt a tablespoon full of oil into each cylinder & see if causes any more resistance. My last B&S, I could not get C/R readings, but it did take a little effort to rotate to adjust the valves.

7394 said:

B&S engines have compression release bumps on the camshaft lobes, so at normal cranking speed it can fool most any compression gauge. (it fooled my compression gauge).
This is done to make the starter have an easier life. Then once started & running higher RPM's compression is restored, then the release bumps are never even noticed in power.

And when setting valve lash on B&S engines, one must find TDC for one cylinder, then rotate engine 1/4" past TDC to get off the C/R bump in cam. Then precise valve lash setting can be accomplished in that cylinder, then repeat procedure.

I've kinda been raised around B&S engines. & my last 2 tractors both had B&S power.

Kohler does not use compression releases, so testing that engine is like an auto engine, Kohler just uses extra strong starters.

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I have not pulled down every type of engine that Kohler ever made so there their might be some that do not have compression release, but I am yet to find one.
Courage engines have centrifugal compression release built into the exhaust valves very similar to the one Honda started using about 3 engine series ago.

Command singles also have the same cr system

Not sure with the Command twins but the Magnum series definately had one as did the Triads.

Kohler starters are no stronger than Briggs starters although they are geared little lower

Decided to tear into the motor this morning. The breather hose was broke . air intake is full of dirt and grass . and there is a noise in upper end of the motor.

Back on Topic: Briggs w/ no compression

RDA.Lawns said:

Decided to tear into the motor this morning. The breather hose was broke . air intake is full of dirt and grass . and there is a noise in upper end of the motor.

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Yeow!! That thing is polluted. Any movement in the valves ?


Bert-

The info about the Kohlers is straight off their website. But Back on Topic to this Briggs with No compression.

Valves are moving I've decided to not go any further with it. Parts starter coils fuel pump about it .

10-4 on that. I understand.