QuestionQUESTION: 7 yr old John Deere LT155 w/ Kohler CV15S-41562. Many times it's hard to start. Sometimes while cutting it will lose power momentarily maybe even die. When it dies it's usually hard to restart with a very good chance of a nice loud muffler backfire. Let it sit a few minutes and it will usually start right back up. Followed the manual's troubleshooting guide, replaced the sparkplug, replaced the seat switch, replaced the air filter, cleaned the carb, still no joy.
Found a post from you on 7/30/07 with similar symptoms where you mentioned a sticking exhaust valve as a possible cause. Pulled the valve cover off and noticed if I compress the intake valve spring it comes right back. Compress the exhaust and it stays until the crankshaft is rotated.
Does this confirm the sticking exhaust valve? How do you recommend I proceed?
Should I completely pull the head off, remove the exhaust valve and clean the valve shaft off (choke and carb cleaner works wonders) then try and put it all back together? (I pulled the outer head bolts so far then realized the carb and muffler still need to come off to get the head all the way off, decided to take a break and obtain conformation I was going down the right path before I start completely tearing it apart)
Also, I noticed while rotating the flywheel that right after the intake valve closes the exhaust valve opens a small amount for a very short time. I assume this is normal since it did it every cycle and I'm guessing it's a form of EGR for exhaust emissions requirements.
Final question, the gasket for the valve cover is just a sealant like some RTV like stuff from a tube I can get at any local auto parts store?
ANSWER: Hello Paul:
You are Going in the Right Direction. I have a Question though. Have you Checked the Gas Tank Pickup Tube and Screen? On Some Model JD Mowers the Tank has a Metal Pickup Tube and Screen. If the Pickup and Screen are Collecting Trash and Rust at the Pickup Screen, then this can Cause the Problem of the Engine Shutting Off Also. From your Description, it Sounds like a Sticking Exhaust Valve and the Exhaust Valve should have Closed when you Released it Not Stay Open Until the Engine was Turned. Use Red (High Temperature) Form a Gasket for the Valve Cover. Any Automotive Parts Retailer Should Sell this. The Exhaust Valve Opening a Small Amount is the Easy Start Compression Release System. This is a Normal Part of the Valve Cycle on this Engine. You can View a Breakdown/IPL of this Engine at this Site Addy, http://www.smallenginepartswarehouse.com/parts.asp and Select the Shop Online Parts Look Up. Then Select the Model Tab. Then Select the OEM and Enter the Model Numbers (CV15S-41562). Then Double Click on the Model in the Results Area. Now you can Select the Section of the Engine you Wish to View. Hope this Helps. I am Here if You Require More Assistance. Let me Know What Happens, Please. Thanks.
Good Luck
Respectfully
John
PS: I am Allowed to Answer 10 Questions a Day. If you See I am Maxxed Out, then Try Submitting your Question at or Just After 9pm EST (US). My New Day Starts then. Thanks.
Respectfully
John
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QUESTION: Had to take it further apart than I wanted to. With the head removed both valves moved and returned smoothly with the same amount of pressure. Using the push rod, the intake valve's lifter internals could be moved in and out ~1/4" while the exhaust valve's lifter wouldn't budge. So out of the chassis it came onto the workbench to open up the crankcase.
Thanks for the link. Smallenginepartswarehouse.com had the lifters (might as well replace both) and a new head gasket. I assume the tube of lube included with each lifter is to be used as an assembly lube on the lifter and cam? Any specific things to look out for on re-assembly? The head bolt inside the valve cover near the intake valve looked like it might have had a sealant on it, did it? Is there a torque spec on the head bolts? Saw the weight & mechanism on the exhaust cam for the compression release, very neat & simple.
Thanks for answering all my questions.
Paul
ANSWER: Hi Paul:
Watch the Internal Governor and Make Sure the Governor Shaft Ear is Over the Internal Governor when Replacing the Sump (Oil Pan). The Torque Specs for the Head is 190 Inch Pounds. There is No Sealant Used on the Head Bolts. The Assemble Lube is Exactly as you Thought is for. The Cam Lobes and the Lifter Mating Surfaces. Hope this Helps. I am Here if You Require More Assistance. Let me Know What Happens, Please. Thanks.
Good Luck
Respectfully
John
---------- FOLLOW-UP ----------
QUESTION: Well I thank you very much, the stuck lifter was it. She starts right up now, no more extended cranking. Used it twice so far and not a single backfire or any loss of power.
I was a little concerned with the torque on the head bolts. All I have is a click style torque wrench and it's lowest setting is 20 ft-lbs (240 in-lbs) I set it where 15 ft-lbs should be, but with the first application of torque, 4 of the 6 bolts click over without moving after been put on and hand snugged with a standard wrench. Backed everything off, reset the torque wrench to 17 ft-lbs to get it closer to it's spec. range and this time snugged everything up with the torque wrench. Still seems a little light for such heavy bolts. But hey it's running fine so it must be right.
Again thanks.
Paul
AnswerHi Again Paul:
Great!! I am Glad it is Running. I Think the Torque is Light Also. However, it was Explained to me that the Aluminum Expands Quicker and Therefore the Head Bolt Torques Increases From the Aluminum Expansion. I Just Use the OEM Specifications Unless I have had Problems with their Specifications and have Found Something that Works Better, like the Valve Specifications. Thanks for the Update and Good Words. Till Next Time. May All Your Mechanical Problems be SMALL ONES and May the All Mighty Bless You and Yours. Thanks Again.
Best Wishes and Good Luck
Respectfully
John
