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Blowing compression out of carburetor. 10HP 28B707

#1

K

kh0432

I have a 10 HP Briggs (28B707) in a rear engine Toro. It was running fine then started to loose power and after shutting it off it would not start. Now its blowing air out of the carburetor. Applied air pressure to the cylinder at TDC and air comes out of the intake. Pulled off the head. Put a flash light into the intake port and can see light around the intake valve seat. The intake valve opens as it should on the intake stroke but doesn't completely close on the compression stroke until the piston is at TDC. Since the exhaust valve seems to be working ok and the camshaft is driven by a gear on the crankshaft, why would the intake valve not be closing properly?


#2

S

shiftsuper175607

kh0432 said:
I have a 10 HP Briggs (28B707) in a rear engine Toro. It was running fine then started to loose power and after shutting it off it would not start. Now its blowing air out of the carburetor. Applied air pressure to the cylinder at TDC and air comes out of the intake. Pulled off the head. Put a flash light into the intake port and can see light around the intake valve seat. The intake valve opens as it should on the intake stroke but doesn't completely close on the compression stroke until the piston is at TDC. Since the exhaust valve seems to be working ok and the camshaft is driven by a gear on the crankshaft, why would the intake valve not be closing properly?
Click to expand...

Did you check the valve clearances?


#3

K

kh0432

It doesn't look like there is an adjustment. According to the parts breakdown the valves work directly off of tappets driven by the camshaft. That's what has me stumped.


#4

Boobala

Boobala

Check your engine breather operation, also this manual may be helpful..........

https://drive.google.com/file/d/0B6NaqjIxWV1ycG8wd0s3Z2Q2X00/view


#5

tom3

tom3

Compression release for easy starting?


#6

B

bertsmobile1

kh0432 said:
It doesn't look like there is an adjustment. According to the parts breakdown the valves work directly off of tappets driven by the camshaft. That's what has me stumped.
Click to expand...

You adjust the valve lash by either grinding some metal off the end of the valve stem to open it up or grinding the valve seat to close it down.
Grinding in these cases is done with wet stones not your angle grinder.


#7

K

kh0432

So would this be caused by wear on the valve face and seat?


#8

T

Tinkerer200

kh0432 said:
So would this be caused by wear on the valve face and seat?
Click to expand...

Sounds to me like the valve seat may be loose in block. Unusual for the Intake to do that. IF that is the case and the block isn't badly wallowed out, the seat can be peened back into place per instructions found in the Service Manual for this engine. First you might want to remove the valve (tappet) cover and make sure that the Intake Valve Keeper has not come off. I think you were given a link for a manual IF you have a problem finding what you want, I can send you a Service Manual.

Walt Conner
wconner5 at frontier dot com


#9

Boobala

Boobala

Tinkerer200 said:
Sounds to me like the valve seat may be loose in block. Unusual for the Intake to do that. IF that is the case and the block isn't badly wallowed out, the seat can be peened back into place per instructions found in the Service Manual for this engine. First you might want to remove the valve (tappet) cover and make sure that the Intake Valve Keeper has not come off. I think you were given a link for a manual IF you have a problem finding what you want, I can send you a Service Manual.

Walt Conner
wconner5 at frontier dot com
Click to expand...

Check post #4 Walt, ... I already sent him the Manual ...... Boo


#10

K

kh0432

Boobala said:
Check post #4 Walt, ... I already sent him the Manual ...... Boo
Click to expand...

Took the intake valve out and ground down the end to get proper clearance. Went to do the exhaust valve and found it was easier to just push the valve off of the tappet with a screw driver and file the end of the valve stem. Runs great now. Thanks for all the help.


#11

K

kh0432

Mower is running great now but I think I took a little too much off of the intake valve as I now have a ticking noise in the valve cover. Do I bother to get a new intake valve and go through the trouble of taking off the head again or just run it as is?


#12

T

Tinkerer200

kh0432 said:
Mower is running great now but I think I took a little too much off of the intake valve as I now have a ticking noise in the valve cover. Do I bother to get a new intake valve and go through the trouble of taking off the head again or just run it as is?
Click to expand...

Run it.

Walt Conner


#13

Boudreaux In Eunice La.

Boudreaux In Eunice La.

You have the L head style engine .............. Did you lap the valves ???? If not you can lap them again or that one valve to get to the proper clearance if it's not but a thousand or 2 out of whack.........

Let us know Mon Ami ~!~!


#14

T

Tinkerer200

"go through the trouble of taking off the head again or just run it as is?"

"If not you can lap them again or that one valve to get to the proper clearance if it's not but a thousand or 2 out of whack."

Run it

Walt Conner


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