Too much compression. adjusted the valves and it got worse

[Albuck]

17.5hp IC
model 31C707-0154-E1

I bought this engine used and used it 3 seasons now. last year it became hard to start. turning the motor by hand past the compression stroke was difficult and thats where it would hang up when I tried top start it.
of the 5 times I started it this season it would only start 2 times on the first try. If I put my battery charger on it I can get it to start. Battery is testing at 12.8 volts and is charging close to 16 when its running.

I went to adjust the valves today. There was more oil then I expected in the valve cover. Maybe 1/2 a cup. The valves were very tight. No gap at all at top dead center. I re-gapped them. guy on you-tube working on the same engine said 6 thousandths on the top and 10 thousandths on the bottom. That's what I did. When I put it back together it did not start, it hung up in the same place as before in the compression stroke.

The motor was even harder to turn then before. almost impossible to turn it by hand.

What do I need to look at next?

Once you've verified your valve settings, remove remove your air cleaner and put a piece of cardboard or the like over the intake tube. If she cranks and starts, it's your compression release. Very simple to check without going nuts.

 

[Richard Martin]

Make sure that one or both pushrods aren't bent too. Both of these pushrods are bent. It's just that one is bent more than the other (obviously).

 

[Travlitt]

In My opinion there is no such thing as Too Much Compression , never saw it in over 50 years on working on all sorts of machine

I too would like to know how you can have too much compression.

 

[LMPPLUS]

17.5hp IC
model 31C707-0154-E1

I bought this engine used and used it 3 seasons now. last year it became hard to start. turning the motor by hand past the compression stroke was difficult and thats where it would hang up when I tried top start it.
of the 5 times I started it this season it would only start 2 times on the first try. If I put my battery charger on it I can get it to start. Battery is testing at 12.8 volts and is charging close to 16 when its running.

I went to adjust the valves today. There was more oil then I expected in the valve cover. Maybe 1/2 a cup. The valves were very tight. No gap at all at top dead center. I re-gapped them. guy on you-tube working on the same engine said 6 thousandths on the top and 10 thousandths on the bottom. That's what I did. When I put it back together it did not start, it hung up in the same place as before in the compression stroke.

The motor was even harder to turn then before. almost impossible to turn it by hand.

What do I need to look at next?

Once you get valves set right, intake .003-.005 and exhaust .005-.007 try it if still to much you may have a bad decompression release requiring a camshaft replacement.

 

[Dreaded]

17.5hp IC
model 31C707-0154-E1

I bought this engine used and used it 3 seasons now. last year it became hard to start. turning the motor by hand past the compression stroke was difficult and thats where it would hang up when I tried top start it.
of the 5 times I started it this season it would only start 2 times on the first try. If I put my battery charger on it I can get it to start. Battery is testing at 12.8 volts and is charging close to 16 when its running.

I went to adjust the valves today. There was more oil then I expected in the valve cover. Maybe 1/2 a cup. The valves were very tight. No gap at all at top dead center. I re-gapped them. guy on you-tube working on the same engine said 6 thousandths on the top and 10 thousandths on the bottom. That's what I did. When I put it back together it did not start, it hung up in the same place as before in the compression stroke.

The motor was even harder to turn then before. almost impossible to turn it by hand.

What do I need to look at next?

I service a lot of mowers and have had to replace several cams. If it had no valve gap meaning the valves were being held open, it should have turned over easy. The less gap you have the easier it should turn over. That being said which from your description it sounds like at some point someone before you got the engine, adjusted the valves real tight to make it start easier. Because cam wear makes the gap larger the only ways they could be too tight is someone adjusted them too tight, the push rod guides are worn, or the cam bearings/bushings have caused the case to wear and, in some way, caused the cam to be positioned closer to the head which is most unlikely. One other thing to check before tearing engine down is the push rod guides, if the (plastic in some cases) guide is worn it can allow the push rod to move out of position and tighten the valves. I have seen this too but, in most cases, it will come out from in under the lifter.
These engines depend on everything being right for them to run correctly.
What I would do in this case (if the push rod guides are good) is to remove the engine and take it apart so I could inspect the cam and can bearing/bushings. Also, if the cam is shown to be worn or the relief is not working you should check the oil pump to make sure it is pumping oil good and has no wear. Because something caused that cam wear or relief problem. Another thing is to look at the cam follower which is caps that ride against the cam and make sure they are free moving.
This sounds like a worn cam that the valves have been adjusted tighter or the push rod guides have worn and allowed the push rod to come out of the indent in the lifter and not completely out from under the lifter.

 

[Dreaded]

I service a lot of mowers and have had to replace several cams. If it had no valve gap meaning the valves were being held open, it should have turned over easy. The less gap you have the easier it should turn over. That being said which from your description it sounds like at some point someone before you got the engine, adjusted the valves real tight to make it start easier. Because cam wear makes the gap larger the only ways they could be too tight is someone adjusted them too tight, the push rod guides are worn, or the cam bearings/bushings have caused the case to wear and, in some way, caused the cam to be positioned closer to the head which is most unlikely. One other thing to check before tearing engine down is the push rod guides, if the (plastic in some cases) guide is worn it can allow the push rod to move out of position and tighten the valves. I have seen this too but, in most cases, it will come out from in under the lifter.
These engines depend on everything being right for them to run correctly.
What I would do in this case (if the push rod guides are good) is to remove the engine and take it apart so I could inspect the cam and can bearing/bushings. Also, if the cam is shown to be worn or the relief is not working you should check the oil pump to make sure it is pumping oil good and has no wear. Because something caused that cam wear or relief problem. Another thing is to look at the cam follower which is caps that ride against the cam and make sure they are free moving.
This sounds like a worn cam that the valves have been adjusted tighter or the push rod guides have worn and allowed the push rod to come out of the indent in the lifter and not completely out from under the lifter.

There is another problem you could have that you need to check if your tear the engine down and that is the valves themselves to insure they are not sticking and slide freely. To do this you need to remove the valve springs. the valves should not have to be pushed in and out they should fall using only their own weight. If you have to push them then carbon build up in the valve guide has to be cleaned out.
So there is a lot more to this than most people can achieve due to mechanical ability. I suggesttaking mower to someone who has experience with reworking small engines.

 

[Gord Baker]

It would appear that you have a Failure of the Automatic Compression Release (ACR) mechanism.
Simply put, it releases some compression during startup. The only cure is to replace the Camshaft to which this is attached to. First, be sure you can obtain a new one From B&S. Aftermarket ones can fail quickly.
There are many tutorials on changing the Cam and bottom Crankshaft seal. I admire your learning on Utube.
Just don't watch the ones where someone is doing a carb over grass!

 

[kjonxx]

When one valve is closed (down) then set the up one to .005. Repeat for the other. Never had a problem. Also you mentioned alot of oil under valve cover could mean overfilled.

 

[Michael72]

17.5hp IC
model 31C707-0154-E1

I bought this engine used and used it 3 seasons now. last year it became hard to start. turning the motor by hand past the compression stroke was difficult and thats where it would hang up when I tried top start it.
of the 5 times I started it this season it would only start 2 times on the first try. If I put my battery charger on it I can get it to start. Battery is testing at 12.8 volts and is charging close to 16 when its running.

I went to adjust the valves today. There was more oil then I expected in the valve cover. Maybe 1/2 a cup. The valves were very tight. No gap at all at top dead center. I re-gapped them. guy on you-tube working on the same engine said 6 thousandths on the top and 10 thousandths on the bottom. That's what I did. When I put it back together it did not start, it hung up in the same place as before in the compression stroke.

The motor was even harder to turn then before. almost impossible to turn it by hand.

What do I need to look at next?

If valves are set correctly and you still have high compression it's your compression release on the cam shaft.. with plug out and justbefore TDC your exhaust vale should bump open a tad to allow compression out for fire up.. if it's a briggs 17.5 intek they are famous for cam issues.. always be sure to check you don't have a snagged belt on transmission or deck too..

 

[justin@justintime]

17.5hp IC
model 31C707-0154-E1

I bought this engine used and used it 3 seasons now. last year it became hard to start. turning the motor by hand past the compression stroke was difficult and thats where it would hang up when I tried top start it.
of the 5 times I started it this season it would only start 2 times on the first try. If I put my battery charger on it I can get it to start. Battery is testing at 12.8 volts and is charging close to 16 when its running.

I went to adjust the valves today. There was more oil then I expected in the valve cover. Maybe 1/2 a cup. The valves were very tight. No gap at all at top dead center. I re-gapped them. guy on you-tube working on the same engine said 6 thousandths on the top and 10 thousandths on the bottom. That's what I did. When I put it back together it did not start, it hung up in the same place as before in the compression stroke.

The motor was even harder to turn then before. almost impossible to turn it by hand.

What do I need to look at next?

you got some wrong info too much clearance on your exhaust valve is what's causing "too much compression" and it's not that it's too much it's just not hitting the compression release set intake (aluminum push rod) to .004" that inches. set exhaust (steel push rod) to .006" INCHES......oil in the cover is expected. if your problem persists, the camshaft's decompression mechanism is probably broken. after you adjust the valves again roll the engine over by hand and you should see a "bump" on the exhaust valve as you come up on the compression stroke.