Craftsman 19 hp, no compression, driving me nuts

16 years ago

Hello all, working on a Craftsman mower with a 19hp motor,model 31p877, type 0121-e1, code 060206ze. The owner stated he was mowing and it started to back fire and then died and would not restart. When I picked this unit up it would back fire thru the exhaust, ok I thought exhaust valve so I pulled the head off. Every thing looked ok, replaced the head gasket at this time also and reassembled. Now there is no compression at all. The push rods seem to be just a little deffernt in length and I have tried them in reverse order with the same result. when I tighten down on the lifter nuts so they are tight (on compression stroke) the intake valve appears to be opening a bit. If the nuts are not tight the lifters are to loose along with the nuts. Should these nuts be tightened down so they are not loose? I have had heads off to do valves and have not come across this before. any information will be welcomed.thanks Ray

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Comments (6)

canguy
16 years ago
The intake valve should open briefly on the compression stroke to release some pressure for easier starting. You should be setting your valve clearances on the power stroke, do the intake first.
raydecker
Original Author
16 years ago
hello all, today after work I tried something with the nuts that hold the rocker arms. I lossened them 1/4 of a turn each and BINGO the engine started right up. They must have been holding the valves open a bit The nuts are loose right now and I know thats not right. what is the clearence settings on both valves ? Next is if the nuts are still loose what would someone do? squeese the rocker to match the nuts hex so it acts as a keeper ? I am on the power stroke as you call it (canguy) ( i call it the compression stroke) Thanks Ray
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CaptTurbo
16 years ago
Seems like you might have to use shims to torque things down and have it all work but it doesn't make sense.
dewaynep
16 years ago
You have to adjust the valves with the piston 1/4" past TDC on the compression stroke. You also have to adjust the valve lash by turning the torx stud (it's in the middle of the nut) and then tighten it down using the nut. It may take a few adjustments until you get it to lock down at the proper lash. Also, make sure the rocker stud is tight in the head, I have seen them loosen up before.
raydecker
Original Author
16 years ago
hello all, Hey Dewaynep you nailed it on the head by telling me about the adjustment on the rocker side of the valves. I did not know about the set screw inside the rocker nut. What a great invention. This was my first bigger engine, so im still on the learning curve. I normaly dont do the bigger engines but it was a friends mower. Thanks Dewaynep I would also like to thank canguy for the input also, Thanks again Ray My friend will be happy he dosent have to push a mower. thanks again ray
baymee
16 years ago
canguy was correct. The compression stroke is the piston going up to TDC and the power stroke begins just after TDC, which is why the 1/4" measurement was given.