Rebuilt engine hard to turn over, but then loosens up?

[Dreaded]

Did you use a ring grove cleaning tool to clean the ring groves before installing the rings? If you did not it may be the rings to tight after sitting overnight. Carbon build up in the groove will cause the ring not to compress all the way.
The cylinder is not perfect, it will have areas the rings compress in more and decompress out as the piston moves up and down. When the engine is hot and has been run some the cylinder has oil on it's surface and so is easier to turn over. But sitting overnight the oil will drain away and leave the cylinder dryer. Usually the engine will stop at about the same location but the tightness of the rings because of carbon build up will cause more friction and stop the piston at it's tightest point.
To clean the ring groves without a ring grove tool I us an old ring. I break off a peice and use it like a scraper to scrape out all the carbon build up in the grove. This way I was taught by my father which was a master mechanic.

 

[kjonxx]

Valves not set right

I have a JD D140 lawn tractor with a B&S 22 hp V Twin engine. I just over hauled then engine and replace the rings because of oil loss. I reinstalled the engine and cranked it over a number of time trying to start it. Wouldn't start got that figured out and started it and ran for a while at varying speeds to break it in. I tried to start it yesterday and it wouldn't turn over. Thought the battery was low on charge. Put a booster battery on and it would crank over. To the top off so I could get to the flywheel. I put a socket on it and it was hard to turn over for a couple of revolutions then got easy. Cranked it over and it started right up. Today it did the same thing. Runs good once I get it started. Any suggestions on what I should do? The first thing I thought was I got the wrong rings, but the end gap was within specs and it cranks over easy after a couple of revolutions. Is it just that tight and will loosen up over time?

Bob

 

[bodean]

I had this happen on my older Vtwin B&S engine that had about 350 hours on it. It became worse over time until it finally got too aggravating to try and start it. I mentioned this to an old retired lawnmower mechanic. He told me this was common and that the valves we’re throwing the timing off and needed adjusting. After re-adjusting the valves a bit looser, everything was back to normal.

 

[DeadmanRoss316]

I personally would check all air gaps, flywheel, pushrods, etc.

 

[Gord Baker]

Wouldn't it be flooded then? Starts right up after I spin it.

What He said. Cylinder(s) may be full of gasoline. Stuck needle valve.

 

[perimeterlandscaping@comc]

as are the vagaries of lawncare business, my 21 mower was run without oil. somoene drained the oil out fo the machine on the trailer. I put new oil and now it starts hard just the way your talking about and then after it warms up it starts on the first pull. the engine sounds like it was run without oil, too low oil. the splash lubrication style crank has to coat itself in oil on a cold start before it can turn freely

 

[Gord Baker]

Too tight of a ring gap

0.004-6" per inch of bore for ring gap.
Check crankcase for fuel contamination of the Oil

 

[unioncreek]

I'm the OP.

You really need to read the posts from the beginning. As I've state three times already the problem has been solved.

I replaced #1 connect rod and the engine is back in the mower and running.

Bob

 

[The Specialist]

There are a few concerns that I have. 1) did you fit an oversize ring? If you did, did you deglaze the cylinders with your ring gap being equal at the top, middle and bottom. 2) if you did number 1 correct, are the timing marks lined up correctly on the crankshaft and the camshaft? 3) if 1 and 2 are done correct, did you set the values just after the compression stroke (so at the beginning of the power stroke) on each cylinder? You might have one cylinder correct, but incorrect on the other cylinder. The fact that it runs, tells me that you did 1 and 2 correct, but your valves are not right

 

[1bbford]

There are a few concerns that I have. 1) did you fit an oversize ring? If you did, did you deglaze the cylinders with your ring gap being equal at the top, middle and bottom. 2) if you did number 1 correct, are the timing marks lined up correctly on the crankshaft and the camshaft? 3) if 1 and 2 are done correct, did you set the values just after the compression stroke (so at the beginning of the power stroke) on each cylinder? You might have one cylinder correct, but incorrect on the other cylinder. The fact that it runs, tells me that you did 1 and 2 correct, but your valves are not right

Come on people if you're going to respond to someone's question, at least take the time to read everything, especially when it is numerous pages of posts. As stated by the OP several times this has been solved with the OP commenting on his progress since day one. And to top things off most of your suggestions and several others were already answered by the OP during the build or during troubleshooting.