John Deere Js20 won't start after i stop to take a 15 minute break.

chevyman984 said:

Ok I replaced the head gasket, put on a shut off valve, rebuild the carb, and oil the autochoke and I mowed for about an hour, stopped for a 15 minute break, same d*mn thing, I pulled five or six time and it started. When I pull it, I sounded like it was popping in the carb. And it does actually feel like it it turns over real easy when I pull it too.

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You have touched on it a few times "when i pul it it turns over easely" clearly compression lost and be hard to start. There is more methods to check like removing the sparkplug squirting a spoonful of fuel/oil mixture replace the sparkplug and start it. It is clear that compression is your problem. You are mowing a large area for the mower size it will need good maintanance

Good luck

PJ said:

You have touched on it a few times "when i pul it it turns over easely" clearly compression lost and be hard to start. There is more methods to check like removing the sparkplug squirting a spoonful of fuel/oil mixture replace the sparkplug and start it. It is clear that compression is your problem. You are mowing a large area for the mower size it will need good maintanance

Good luck

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I've always give it good maintenance. If something wasn't kept up, it wasn't me, it was jackleg that. I've got it from. When I got the dern thing the oil was thick as crap. Ill get a tester and check compression

EngineMan said:

Well you come back and let us know how you do, the only thing I will say is, just take you're time and look things over and do part by part, am sure you will win in the end, in the mean time all the best.

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Thanks engineman. I just got back from town and I got everything. Believe it or not I couldn't even find a air filter or precleaner. I replaced them both at the beginning of 2012 mowing season so I might be able to get by with not getting them quite yet.

Ok finnaly found a compression tester!!!!! It is 82 psi cold, and 46 after running an hour. I'm assuming 46 is low???

chevyman984 said:

Ok finnaly found a compression tester!!!!! It is 82 psi cold, and 46 after running an hour. I'm assuming 46 is low???

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46 yes very low even hot, cold should be up at around 100psi, what engine is it. not sure if you post it up I did have a look just didn't find it if you did.

Its either the 675 series briggs and stratton or the 6.75 horspower briggs and stratton.

If its a briggs they don't give you compression readings, but this may help you pin point the problem.

Check Compression
Use Leakdown Tester #19545 to check the sealing capabilities of the compression components.
Follow the instructions provided with the tester to perform the leakdown test.
NOTE: Any air leaks at the connections or fittings of the tester will affect the accuracy of the test.
Listen for air leaking from the cylinder head gasket, carburetor, exhaust system, and the crankcase breather tube.
Air flowing between the cylinder and cylinder head indicates that the cylinder head gasket is leaking.
Air flowing from the carburetor indicates air is leaking past the intake valve and seat.
Air flowing from the exhaust system indicates air is leaking past the exhaust valve and seat.
Air flowing from the crankcase breather tube or high oil fill dipstick tube indicates air is leaking past the piston rings.
Possible Causes for Poor Compression:
Loose cylinder head bolts
Blown head gasket
Burned valves, valve seats and/or loose valve seats
Insufficient tappet clearance
Warped cylinder head
Warped valve stems
Worn bore and/or rings
Broken connecting rod

I know the cylinder walls are worn because when I had the head off to replace the gasket, it was kinda dark looking and had no cross hatching left at all, and just got through adjusting the rpms. And I have a question enginman, when you hit thick grass, and the engine bogga down, shouldn't the governer pick the rpms back up, because it bogga down in the slightest bit of grass, a.d if I keep the mower mowing through the grass, the engine stays "bogged down" it does t pick itself back up.

Yes the governer should pick it up but engine has to be near 100% other things how come into play...! check the links and make sure the governer is working, check also the valves one or maybe two are staying open a little and that would give less compression, you never know. do other test this time with a little oil in cylinder if you get a higher reading its rings, and if you don't can be valves/head gasket etc.

Well I assume the governer works because it mowes, and never have any problems over revving. I will try oil in the cylinder in a minute