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I need help.....

#1

A

Affordable in Indy

I'm working on a B&S two cylinder engine 44K777-0125-G on an Exmark zero-turn. The exhaust valve seat came out of one of the heads. The valve got stuck open. That allowed the push rod to pop out of position. It ended up twisted and mangled inside the engine which also destroyed the camshaft.

I installed a new OEM camshaft and tappets. I got the valve seat pushed back in. I also tapped around the exhaust valve seats on both heads with a center punch to create small divots in the aluminum to keep the valve seats from coming out again. That is a procedure recommended by mechanics I follow online. I installed new head gaskets, push rods, rocker cover gaskets, sump gasket and sump oil seal. The valve clearances are set at .004

When I tested it out, It did not go well. The engine was making some sort of a popping noise, not really backfiring. When I drove the mower around, it seems sluggish. When I engaged the blades, the engine completely died. It has no power. Compression test shows 52 PSI on both sides. I checked the flywheel key. It's fine. I double checked the valve clearances. They are still at .004. My only guess right now is that the aftermarket head gaskets I used could be bad. Does anyone have any other ideas?


#2

D

digr

Isn't .004 a little tight for a exhaust valve?


#3

B

bertsmobile1

Do a leak down test you may has shifted one of the seats just enough to prevent the valves from seating
Now check the cam timing because it is easy to end up being 1 tooth out .
1 tooth advanced = won't start
1 tooth retarded starts well but no power & won't rev out
Also try with the kill wires removed from the coils
Let us know what you find .


#4

Tiger Small Engine

Tiger Small Engine

Affordable in Indy said:
I'm working on a B&S two cylinder engine 44K777-0125-G on an Exmark zero-turn. The exhaust valve seat came out of one of the heads. The valve got stuck open. That allowed the push rod to pop out of position. It ended up twisted and mangled inside the engine which also destroyed the camshaft.

I installed a new OEM camshaft and tappets. I got the valve seat pushed back in. I also tapped around the exhaust valve seats on both heads with a center punch to create small divots in the aluminum to keep the valve seats from coming out again. That is a procedure recommended by mechanics I follow online. I installed new head gaskets, push rods, rocker cover gaskets, sump gasket and sump oil seal. The valve clearances are set at .004

When I tested it out, It did not go well. The engine was making some sort of a popping noise, not really backfiring. When I drove the mower around, it seems sluggish. When I engaged the blades, the engine completely died. It has no power. Compression test shows 52 PSI on both sides. I checked the flywheel key. It's fine. I double checked the valve clearances. They are still at .004. My only guess right now is that the aftermarket head gaskets I used could be bad. Does anyone have any other ideas?
Click to expand...
A job like this can end up to be a very time consuming deal. Sounds like you will be removing engine and going back in deep. Chalk it up to be a great learning experience. Definitely do a leak down test, because excessive leaking from intake or exhaust valves sounds like a real possibility in your case. Peening valve seats is an approved repair method from Briggs and Stratton. However, it must be done correctly as your results may vary.


#5

R

Rivets

If you peened the valve seats in you also need to at least relap the valves, if not recut the valve seats and faces. Valves seats can be easily cocked which will not allow them to seal properly.


#6

A

Affordable in Indy

Thank you for the replies. Here's an update:

I did the leak down test. This was my first time doing that. The pressure pushed the piston down. It was do longer at TDC and the exhaust valve was open. Is that normal? I had to use a wrench on the flywheel nut to hold it at TDC. At that point, the test was in the green on the meter on both cylinders. 20% loss on one side and about 30% on the other. I sprayed soapy water on the heads while under pressure to check for leakage from the head gaskets. Honestly, I've never heard of people doing that. I just made it up. I figured that it couldn't hurt. I didn't see any bubbles from that.

At this point, I think I'll reconfirm that I have spark on both sides and recheck valve clearances. Besides that, I think I'll have to check the timing on the camshaft. Does anyone have any other ideas?


#7

I

ILENGINE

Could of got the camshaft 1 tooth off and that would cause issue. May be worth going back and checking the flywheel key because if not properly torqued at the onset can shear on start up and make you want to pull your hair out.


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