Briggs Vtwin Turnsover and Bumps Back

[slomo]

No both were pretty clean in black carbon build up.

Pictures would be helpful.

 

[davbell22602]

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.

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.

 

[davbell22602]

Tried posting pics but too large when posting from phone.

 

[davbell22602]

20220713_192018.jpg

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Cylinder #2

20220713_192049.jpg

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[davbell22602]

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

 

[slomo]

Camshaft doesn't have compression release on it

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

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

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.

Camshaft doesnt have compression release on it

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.

 

[slomo]

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

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.

 

[davbell22602]

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.

 

[davbell22602]

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.

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.

 

[slomo]

Part number for the camshaft is 790562

Briggs 790562 shows a compression release.

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