Too Much Compression

loneeagle

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Have a JD L100. Starter will not turn engine over. New starter and battery. It's like it has too much compression. Is there a pressure release on engine? Gets to a point I can't even move by hand.

Thanks
 

ILENGINE

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The compression release operates off the camshaft, opening the intake valve slightly before top dead center. I am assuming it is a Briggs engine. It is a fairly common occurance for the valves to get out of adjustment. Remove the valve cover, remove the spark plug, position the piston slightly past TDC with both valves closed. Set the valve gap at .004-.006 for both valves, and see what happens. If that doesn't fix it post back and either me or Rivets will help you out.
 

loneeagle

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Tried adjusting the valves and it still has the high compression spot. Could you please instruct me on the next step?

Thanks,

mack
 

Rivets

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Post your engine model numbers and I will find you a manual which will explain how to adjust valves.
 

loneeagle

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Hi Rivets,

Adjusted the valves as descrived by ilengine above. Is there more I need to do as far as valves?

Thanks
 

Rivets

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When you adjusted the valves, did you look to see if the compression release was working? I do valve adjustments the same way ILengine does with one change. After each adjustment, I rotate the engine through three complete cycles and then recheck each gap again until I get the proper reading twice in a row. Only then do I go to the other valve. While doing this I watch the action of both valves to make sure that I see the exhaust valve open slightly before each compression stroke. By doing this, I can make sure that the compression release is working and that I get the proper gap on each valve. The one thing that ILengine did not say, but I think he assumed, that you must make sure that you do the adjustment slightly passed TDC on the compression stroke only. If the valves are out of adjustment, both valves could be closed between the intake and exhaust strokes. Finally, does the engine turn over smoothly, using the starter, with the spark plug removed?
 

ced

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Does anyone know for sure which valve, intake or exhaust, is used for compression release? I have seen both mentioned in this thread. I am having the same issue in a 19.5 single cyl briggs in a JD la115.
 

Rivets

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Older engines used the exhaust valve, while the newer ones are using the intake valve. I may be wrong when I said exhaust in my last post.
 

ILENGINE

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The one thing that ILengine did not say, but I think he assumed, that you must make sure that you do the adjustment slightly passed TDC on the compression stroke only.

I alluded to it, but didn't explain it very well
 

ILENGINE

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Does anyone know for sure which valve, intake or exhaust, is used for compression release? I have seen both mentioned in this thread. I am having the same issue in a 19.5 single cyl briggs in a JD la115.

the compression release works of the bottom valve of the engine, which with the briggs OHV cross flow head is the intake. Part of the compression release on the intake valve as compared to the older exhaust valve engines is due to emissions. Don't want to spit raw gas out the exhaust. The older flat head engines, the exhaust was used for the compression release, but if you think about it the exhaust valve was closer to the side cover on horizontal engines, or the oil pan on verticals. Compression release mechanism located next to the camshaft gear.
 
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