More on my bad running Massey 175

As I have previously written I picked up a Massey 165 Perkins gas. Runs but poorly. Good spark. No blowby but misses. It had been sitting for about 4 years. I have started and idled it but did not drive it due to a bad rim. Once again I have really appreciated the help. Thanks for being here.

This is what I have done. I can hear air leaking out the exhaust at idle. I thought stuck valve so pulled the valve cover. Everything at first glance looks good. I then started it and all valves moved and all had clearance from valve to rocker. Did not measure but when one valve open there was clearance.
I checked compression. My gauge appears ok.
1. 170
2. 65
3. 170
4. 175



As I said I can hear air hissing at exhaust. I did not look at the springs specifically. I tested it warm with all plugs out full throttle.
Will this come out of it as it might have some carbon or rust on it? Burnt valve? Broken spring? I hate to pull the head if I don't have to and no there is no blowby. Any ideas?

Thanks.
 

I had a broken valve spring on my FE35 that gave similar results . It was hard to spot easily and took a little rotation of the engine and poking around with a screwdriver to find .
I replaced it without removing the head . Remove the plug on that cylinder , rotate the piston to the lowest position , feed in as much clean soft sash cord as you can leaving a good bit hanging out . Rotate the engine[ by hand ] to compress the cord , this will jam the valve into the head and let you remove the collets to change the spring . Rotate the engine to loosen the rope and remove .
 
(quoted from post at 15:19:36 08/18/16)
I had a broken valve spring on my FE35 that gave similar results . It was hard to spot easily and took a little rotation of the engine and poking around with a screwdriver to find .
I replaced it without removing the head . Remove the plug on that cylinder , rotate the piston to the lowest position , feed in as much clean soft sash cord as you can leaving a good bit hanging out . Rotate the engine[ by hand ] to compress the cord , this will jam the valve into the head and let you remove the collets to change the spring . Rotate the engine to loosen the rope and remove .


To replace a valve spring with the head on the "cord in the cylinder" is the way I do them.
 
Just went out and looked at it again. I just can't see
a broken spring. Push down on it with a
screwdriver and feels as strong as the others. Only
difference is the others have a solid tink sound
when shut and this valve has a tunk sound. Maybe
valve head damages. It has some smoke but I
have been running it on gas from my 2 cycle boat
engine. When running no bubbles in radiator.
 
I'll bet the exhaust valve face and seat area are burned, or corroded away from setting. Diesel exhaust valves will do it too. Use a leak down tester on that cylinder with both valves closed, I'll bet you hear the air leak at the exhaust when the air is applied through the plug hole.
 
(quoted from post at 16:37:38 08/18/16) Just went out and looked at it again. I just can't see
a broken spring. Push down on it with a
screwdriver and feels as strong as the others. Only
difference is the others have a solid tink sound
when shut and this valve has a tunk sound. Maybe
valve head damages. It has some smoke but I
have been running it on gas from my 2 cycle boat
engine. When running no bubbles in radiator.



The exhaust valve was probably just off the seat after the tractor was last parked, and some rust formed around the valve face, and valve seat. On some engines it is possible to see a part of the valves through the spark plug hole, don't know if you can do that on your engine.
 

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