QuestionQUESTION: I have a MTD snowblower with a Tec HSSK50; family YTPXS.195 that will take 15 pulls to start then will only run @ high idle. It began last winter by backfiring and loss of power in 1" of snow. I Replaced: Carb, fuel line, plug, cleaned combustion chamber (thought is was lean from too much carbon), new Head Gasket, Checked Flywheel key (Not sheared), adjusted Governor. (Inet search), still will not run. It may run, but dies when I try to idle, and will backfire. It gets spark, begins to run slow at first then speeds up and has no power. Nothing I have done has helped, nor has it made it worse. What did I miss? Thank you, I appreciate any help!
ANSWER: Hello Jeff:
From your Description it Sounds like a Burnt Valve or Improper Valve Clearance. The Following is a Basic Instruction File for Setting the Valve Clearances on Non OHV Engines. Any Input is Appreciated. On this Model Engine I Usually Suggest Reseating the Valves if the Valve Clearance Requires Adjusting. The Following is a General Instruction File for Setting the Valve Clearance on Non OHV Engines. **Remove the Carburetor and the Crankcase Breather/Vent and the Valve (Stem) Cover so you have Access to the Valve Stems, Springs and Keepers. Set 1 Cylinder to TDC on the Compression Stroke. Using a Blade Style Feeler Gauge, Check the Clearances. The Intake should be .005in - .007in and Exhaust .008in - .010in. If the Feeler Gauge will Not Slide Between the Valve Tip and the Tappet, then you Must Reset the Clearances. **You Will Require a Small Engine Valve Spring Compressor to Remove the Springs and Keepers from the Valve Stems.** Some Engines Use a Valve Keeper that is like Automotive Keepers (2 Cone Shaped Keepers that Set in the Valve Retainer/Rotocoil Assembly)and the Other Style is a Slotted Retainer that is Moved (once the Valve Spring is Compressed) to the Larger Opening in the Retainer and the Retainer Slips Over the Valve Stem Tip for the Valve to be Removed. Remove the Heads. Set 1 Cylinder so the Piston is at TDC on the Compression Stroke And Check the Clearances Between the Valve Stem Tip and the Tappet. The Clearances are as Follows: Intake Valve Clearance is .005in - .007in and the Exhaust is .008in - .010in. You have to Lightly Grind the Valve Stem Tip and Place the Valve Back Into the Engine (you can Hold the Valve Seated by Hand) and Check the Clearance Until you Reach the Required Clearances. **++** For this Engine Model I Suggest you Reseat the Valves while you are Setting the Correct Valve Clearance. For this you will Need a Small Valve Seat Suction Tool. This can Usually be Purchased for $10.00us and has a Suction Cup that Hold the Valve Head so you can Turn the Valve Back and Forth and Dress up the Valve Seat. Valve Grinding Compound is Approximately $5.00us a Tube and a Tube Last the Shop About a Year. It Doesn't Take a Lot to Reseat 1 Engine.**++** Once the Valve Clearances are Reached and the Valve Seat is Nice and Dull; Re-Install the Valves on that Cylinder and Turn the Other Cylinder to TDC on the Compression Stroke and Set that Cylinders Valve Clearances. Once that Cylinder is Set, then Re-Assemble the Engine.** You can View a Breakdown/IPL of this Engine at this Site Addy, http://www.outdoordistributors.com/ and Select the T. Then Select Tecumseh. Then Select Don't have Part Numbers. Then Enter the Model Numbers. Then Select your Model and Download the File for Online Viewing. If you Hit a Snag or this Does Not Correct the Problem, I am Here if You Require More Assistance. Hope this Helps. Let me Know What Happens, Please. May the All Mighty Bless You and Yours. 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 8pm EST (US). My New Day Starts then. Ratings and Comments are Greatly Appreciated. Thanks.
Respectfully
John
---------- FOLLOW-UP ----------
QUESTION: John, thanks you were right on! Intake was to spec, exhaust was 0 gap. I removed both valves and cleaned and polished the shafts. I ground the exhaust to be .0085 gap. Put all back together and it started on the first pull!! Awesome!! I cannot thank you enough. My follow up question is what would cause the valve to either gain in length, or is the tappet deforming? Will I need to do this again soon, or should I replace the tappet assy as well?
Thanks again, Jeff. P.S. it ran from WOT to idle for teh first time since last winter!
Thanks again.
AnswerHello Again Jeff:
Great!! I am Glad it is Running. Over Time the Valve Stem Stretches Due to the Heating and Cooling of the Metal. The Exhaust Valve is the Worst for Stretching as the Temperatures are Hotter on the Exhaust Valve Stem than the Intake Stem. Usually Once or Twice During the Life of a Small Engine will you have to Set the Valve Clearance. This is Not So with the OHV Engines. The OHV Engines Require the Valve Clearances to be Set About Every 3 Years. Do Not Replace Anything, All will be Good. 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
