Hmmm, Did I lose the Compression Release on my 19.5 HP OHV motor?

Jrork

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  • / Hmmm, Did I lose the Compression Release on my 19.5 HP OHV motor?
Hi guys. My father in law gave us his older John Deere LA 115 that has suddenly stopped wanting to start. He put a new battery in it but with no luck so he bought a new JD and gave his old one to us.
It seems to be dealing with the hard start issue like so many others. It rolls over great with the plug pulled but wont start with it in. I can manually roll the motor just past TDC and then hit the key and the momentum generated by the starter will often allow it to roll over enough to start but without doing that, it won't turn over.

So, I assumed that the valves were way out of adjustment so I pulled the cover only to find that the valves appeared to be adjusted fine. Regardless, I backed the rockers off and rolled it to the 1/4' past TDC approach and adjusted them 4 & 4. Tried to start it and no luck. Then I backed off the rockers and adjusted them with the EO/IC approach that I'm more familiar with. Still no luck. I then turned over the motor by hand and watched for the little "bump/wiggle" of the compression release mechanism function and was unable to see it which makes me worried that the mechanism has failed.

I also double checked all the electric connections just to be sure but they were fine. Sooo, am I looking at pulling the motor or is there another troubleshooting trick you would suggest trying first?

19.5 hp
Modell 31P677
Type 0832 B1
Code 080826ZD

The hour meter shows 233 and it once started, runs flawlessly

Thanks in advance for any tips or advice you could share........john
 

Tinkerer200

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  • / Hmmm, Did I lose the Compression Release on my 19.5 HP OHV motor?
When adjusting valves you should use the proper information. .004" is OK for the Intake which is the key valve for compression release on this engine .003" - .005" being the range. .005" - .007" the range for exhaust but that isn't causing your problem. Assuming you did the adjustment as you said and did not see any additional movement to completely close the intake half way or so up on compression stroke, you are probably right that the compression release is broken which is fairly common with this engine.

I can send you a Service Manual for your engine if you like, address below, put in proper format and remind me engine model number and what you want.

Walt Conner
wconner5 at frontier dot com
 

Jrork

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  • / Hmmm, Did I lose the Compression Release on my 19.5 HP OHV motor?
Thanks a ton Walt. Email has been sent
 
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  • / Hmmm, Did I lose the Compression Release on my 19.5 HP OHV motor?
Jrork if you do have a bad cam I think I have a used one that will fit your engine ~!~!

Plus Tard Mon Ami ~!~!
 

Jrork

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  • / Hmmm, Did I lose the Compression Release on my 19.5 HP OHV motor?
Well, it looks like I'm going to need to do something for sure. I wanted to make sure I was not missing something so I adjusted the valves once again with no luck. Just to make sure my old eyes were fooling me, I rigged up a dial indicator against both of the rocker arms and rolled the motor over looking for the little "bump" that would the compression release with zero luck. I'm really thinking that I lost my compression release and now need to look into pulling the motor.....
 

Jrork

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  • / Hmmm, Did I lose the Compression Release on my 19.5 HP OHV motor?
Well, popped the motor out and pulled the bottom plate off and sure enough, the compression release was laying in the sump along with the hardened pin and spring. Looks like a new cam and gaskets and we should be up and starting again...
 

Jrork

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  • / Hmmm, Did I lose the Compression Release on my 19.5 HP OHV motor?
Well, slapped it all together and it fired right off. So simple and this old mower is good for alot more hours. Thanks for the help.
 
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