Export thread

446677
0470-E1
050310YG

Sears GT5000 917.276310 48in cut gear drive

Got this on trade earlier this year in the spring. Diagnosed it last year in of having 3 of 4 pushrods missing and the 4th one was bent. Plus oil leak also. Recently split crankcase and found loose crankcase bolt which is probably why it leaked oil. Found bent steel pushrod inside the crankcase but the other 2 are missing in action. Replaced all 4 pushrods and crankcase gasket. Set the valves to .005 on the compression stroke 1/4 turn past TDC as manual says too for each cylinder. When exhaust pushrod is in cylinder #2 the engine goes into a bind and bends it. Engine will roll over just fine by hand when its not in there. Exhaust valve will open by hand when using the rocker arm to open it. It will not open the exhaust valve with rocker arm instead it bends the pushrod. I set to .005 on loose side this last time when it bent the 2nd exhaust pushrod on cylinder #2. Timing marks are lined up inside the crankcase. Is it possible to have a bent exhaust valve in the guide?


Here's pics of the bent pushrods found tearing this engine.






Here's pics of the cylinderhead from cylinder #2 where it keeps bending pushrods.

Take out the cam and put up a few pics of the lobes.

Here's pics of the camshaft.

The one closest to the gear looks squirrelly, can you take some better pics of the lobe tip?

Fish said:

The one closest to the gear looks squirrelly, can you take some better pics of the lobe tip?

Click to expand...

I can get better pics but both exhaust valve lobes are borderline of the reject size of needing a camshaft. Intake lobes are 1.235 and exhaust are 1.225.

Check the location of the guide itself. When overheated, the exhaust valve guide will sometimes move. Sometimes it moves toward the head, holding the valve open, causing that cylinder to not fire. If the guide moves the other way, it will interfere with the rocker and cause the pushrod to bend. gregjo1948

gregjo1948 said:

Check the location of the guide itself. When overheated, the exhaust valve guide will sometimes move. Sometimes it moves toward the head, holding the valve open, causing that cylinder to not fire. If the guide moves the other way, it will interfere with the rocker and cause the pushrod to bend. gregjo1948

Click to expand...

Guide didnt move.

Here's pics of the lobes.

davbell22602 said:

Guide didnt move.

Click to expand...

In the picture showing the piston side of the head, the guide on the left looks like it is up in the head much farther than the other guide. gregjo1948

gregjo1948 said:

In the picture showing the piston side of the head, the guide on the left looks like it is up in the head much farther than the other guide. gregjo1948

Click to expand...

That's how it shows it in Briggs manual also. Briggs manual didn't say on how far out it can be.

davbell22602 said:

That's how it shows it in Briggs manual also. Briggs manual didn't say on how far out it can be.

Click to expand...

Just be sure the guide isn't interfering with the rocker causing bent push rod. gregjo1948

pauly50

picture of your valve guide shows the valve head side of guide flush ,(effect) it should be the same as the other valve guide protruding into throat the same amount, spring and collett retainer hitting top of valve guide and stops solid , camshaft and push rod continue to move upward and bends pushrods ,(effect) no choice but to replace cylinder head, sorry to say ,( cause ) is overheating and or insufficient lubrication

note the other possiblity is decompressor not working , check decompressor mechanisim on camshaft carefully

pauly50 said:

pauly50

picture of your valve guide shows the valve head side of guide flush ,(effect) it should be the same as the other valve guide protruding into throat the same amount, spring and collett retainer hitting top of valve guide and stops solid , camshaft and push rod continue to move upward and bends pushrods ,(effect) no choice but to replace cylinder head, sorry to say ,( cause ) is overheating and or insufficient lubrication

note the other possiblity is decompressor not working , check decompressor mechanisim on camshaft carefully

Click to expand...

How you know its suppose to be like that. Briggs manual shows it differently on the valve guide on the exhaust.

davbell22602 said:

How you know its suppose to be like that. Briggs manual shows it differently on the valve guide on the exhaust.

Click to expand...

I worked on 2 in the last month that happened to. The 2 I worked on recently, both had the exhaust guide move towards the piston. After moving too far, the guide will hold the valve open and the cylinder will stop firing. I was able to repair both and so far, they're still mowing. gregjo1948

gregjo1948 said:

I worked on 2 in the last month that happened to. The 2 I worked on recently, both had the exhaust guide move towards the piston. After moving too far, the guide will hold the valve open and the cylinder will stop firing. I was able to repair both and so far, they're still mowing. gregjo1948

Click to expand...

Do you have a photo of what one looks that hasnt moved so I can compare it with mine and use for future reference.

davbell22602 said:

Do you have a photo of what one looks that hasnt moved so I can compare it with mine and use for future reference.

Click to expand...

I have no picture. gregjo1948