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445777
0263-E1
031229YG

Turns over fine when sparks plugs are removed
Camshaft doesnt have compression release on it
Already has a new starter
Battery has 12v and 12v load
valves adjusted to .004 to .005
Someone on facebook group page said bad camshaft but not following how it could be bad camshaft since theres no compression release.
Im down to replacing the cylinderheads unless theres some else im missing here.

Bad camshaft lobes are a possibility but easily check for by comparing rocker movement. They should be equal for both intake and exhaust. Also check for a sheared flywheel key which would ignition timing problems.

Could you do a compression test? What do the spark plugs look like?

StarTech said:

Bad camshaft lobes are a possibility but easily check for by comparing rocker movement. They should be equal for both intake and exhaust. Also check for a sheared flywheel key which would ignition timing problems.

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Flywheel key is good. I removed both heads. Exhaust valve on cylinder #1 is catching/sticking when i open it my hand while valves still attached to the head.

ESully said:

Could you do a compression test? What do the spark plugs look like?

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Both heads been removed. When customer dropped mower off they to keep turning it on/off to get it to start. Came with deck belt issues. Now it wont even start for me. Spark plugs are normal.

Here is what I think Star Tech is talking about. Note the lobe closest to the gear.

Fish said:

Here is what I think Star Tech is talking about. Note the lobe closest to the gear.

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Yes I understand. Both valves on both heads opened and closed the same before removing the heads. I guess i have to open it up and visually look at the camshaft and measure the lobes and compare to what the briggs spec is for this engine before replacing the heads.

Was there a buildup of carbon on the heads?

Fish said:

Was there a buildup of carbon on the heads?

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No both were pretty clean in black carbon build up.

If I read you correctly, sounds like an overheat condition. Valves and guides got hot. You said exhaust valve (hot potato) was sticking.

Block and cooling fins clean and clear of all grass, oil, grit and bugs? I mean all the way around each cylinder, behind mufflers and such. Clean as in clean. Clean as in a new engine clean.

davbell22602 said:

No both were pretty clean in black carbon build up.

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Pictures would be helpful.

slomo said:

If I read you correctly, sounds like an overheat condition. Valves and guides got hot. You said exhaust valve (hot potato) was sticking.

Block and cooling fins clean and clear of all grass, oil, grit and bugs? I mean all the way around each cylinder, behind mufflers and such. Clean as in clean. Clean as in a new engine clean.

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Yes its pretty grassy in the front where the carb and linkage are. Still doesn't solve it not turning over. When I force it by hand it doesn't bend any pushrods.

Tried posting pics but too large when posting from phone.

Cylinder #2

Any thoughts on the pics? heads or more likely camshaft without opening the crankcase with measuring the cam lobes?

davbell22602 said:

Camshaft doesn't have compression release on it

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On a 25hp twin engine? Sounds rather odd. I bet it does.

davbell22602 said:

Exhaust valve on cylinder #1 is catching/sticking when i open it by hand

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Not normal. Hot exhaust valve alert. Again I would look at the cooling fins and block. Are they shiny silver like a new engine as in super clean?

Pull the valves on the sticking head. Might have to reem the guide and do some polishing. Get the sticky exhaust valve moving proper again.

davbell22602 said:

Camshaft doesnt have compression release on it

Click to expand...

Is it laying in the bottom of the oil sump now?

Battery been load tested? Solenoid good? You said it cranks fine with the plugs removed. Put one plug in and see slash LISTEN to it crank. Sound normal while cranking? If so repeat on the opposite cylinder. Then install both plugs.

Symptom being a kickback normally is timing off or valves out of proper adjustment. Engine loaded up with carbon...... Or a sticking closed, overheated exhaust valve.

davbell22602 said:

Yes its pretty grassy in the front where the carb and linkage are. Still doesn't solve it not turning over.

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What is grassy? Dirty, oily, stopping the fins from cooling the engine?

I know the above doesn't stop it from turning over. It could be what caused it to do what it is doing now. You reported a sticking exhaust valve.

Dude, you have to clean the block and cooling fins all the way around each cylinder. As in spotless looking like a new engine. These are air cooled engines. Aluminum block and heads..... Keeping the fins clean is critical. It's a yearly maintenance item in yours and every other mower engine manual out there. Meaning we ALL must clean these fins and block yearly or more often if you bag.

This is a screen snap of your engine manual. See where it says clean cooling system? This is what I am talking about. Notice the interval?

Also notice the last item? Remove combustion chamber deposits? That means pull the heads. Clean the carbon off and all around the valves too.

I can turn over hand when forcing it but its not bending any pushrods. Part number for the camshaft is 790562, All the pics shows no compression release.

slomo said:

On a 25hp twin engine? Sounds rather odd. I bet it does.

Not normal. Hot exhaust valve alert. Again I would look at the cooling fins and block. Are they shiny silver like a new engine as in super clean?

Pull the valves on the sticking head. Might have to reem the guide and do some polishing. Get the sticky exhaust valve moving proper again.


Is it laying in the bottom of the oil sump now?

Battery been load tested? Solenoid good? You said it cranks fine with the plugs removed. Put one plug in and see slash LISTEN to it crank. Sound normal while cranking? If so repeat on the opposite cylinder. Then install both plugs.

Symptom being a kickback normally is timing off or valves out of proper adjustment. Engine loaded up with carbon...... Or a sticking closed, overheated exhaust valve.

Click to expand...

Wont turnover with plugs installed. battery is 12v load tested. yes solonoid good, If the solonoid wasnt good it wouldnt crank reguardless if the plugs were installed or not.

davbell22602 said:

Part number for the camshaft is 790562

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Briggs 790562 shows a compression release.

I confirm what you said per Briggs parts list for your engine. Briggs 790562 IS the correct cam.

Your date code - 031229YG

All pictures online doesnt show a compression release on the camshaft.

My pictures came from the Briggs and Stratton store. Even put the link up for you.

It was the first hit on Google.

Both pictures show a shaft, 2 lobes, 1 gear and this funny finger like metal part with a spring.

This is vtwin engine not single cylinder.

I used what you wrote for your engine numbers

445777
0263-E1
031229YG

Found your cam at the briggs store. Unless they posted the wrong pic??? Could be......

Just hit me. Thanks for the correction. Your twin should have more lobes. My bad.... Wrong pics from briggs store.

This is the cam pic from your parts diagram at the briggs store. More lobes all around.... Again MY BAD. Sorry for the poor detective work.

So can worn cam lobes cause it to not turnover with plugs installed?

Well & good Slowie,
But that is a single cylinder cam & Dave has a V twin
AFAIK the biggest B & S single is 20Hp
Right at the start Dave posted
445777
0263-E1
031229YG

Dave,
Try closing down the gap on the inlet valves , one at a time
This means they will open latter so let less air in thus at full compression there will be less in there to compress
Some cams actually have a bit of a bump in them to decompress usually through the exhaust that at running speed the follower passes over
An idea originally used by Levis motorcycles from memory
If tightening the valve lash works then you know the cam is on the way out
I have customers mowers with a lash on the inlets are down to 0.001" because the cam / followers are wearing down & the owners does not want to pay for a replacement .

Try powering the starter by jumping from the battery + directly to the + terminal on the starter
Starter cranks the engine over means that one of the power cables or solenoid is faulty
Do the same with the - side to a good ground
Starter turns the engine over = high resistance on the ground cables

If the starter can still not turn the engine through compression, try jumping directly from your car / truck
If it turns the engine over properly then you battery is cactus

bertsmobile1 said:

Well & good Slowie,
But that is a single cylinder cam & Dave has a V twin
AFAIK the biggest B & S single is 20Hp
Right at the start Dave posted
445777
0263-E1
031229YG

Click to expand...

All correct.

Again I disclosed MY mistake to all on here.

Sorry the web site thebriggsstore.com got me astray with their pictures.

No longer have this mower. I narrowed it down to something electrical. Thanks for the help.