QuestionHi John,
I have a Troy Built Rototiller, vintage 1976, that won’t run at high speed after
it warms up for about 10 minutes, and not too well at low speed either when
it’s hot. I let it cool down and then it runs fine for another 10 minutes the
next day, although it does sputter a little at high speed. I just replaced the
carburetor, piston rings, cylinder head, cylinder head gasket, points, spark
plug, condenser, fuel filter and air filter. The fuel tank filler cap is not on too
tight (no vacuum). There is always spark although I honestly can’t vouch for
the quality of the spark. The spark appears to be the same whether the
engine is hot or cold. All new gas in the tank. I notice that when it does start
running badly and quits on me that it will sometimes backfire when it quits
running. It is not sucking any air around the carburetor joints. Compression
drops from about 115 PSI when it’s slightly warm to around 55 PSI when it
won’t run. Not sure about the compression at cold until tomorrow. I’m really
pulling my hair out on this one. Is it possible the new piston rings/cylinder
is/are the problem. The cylinder was de-glazed and there where no gouges
in the cylinder wall. Any ideas? If you think it’s valve related, then could you
give me an idea what I need to do to correct the problem. If I need new
valves, should I buy standard or 1/32 inch OS? Thanks in advance for your
help! Model number of the Tecumseh motor is HH60-105102F.
AnswerHello Chris:
I Noticed you Did Not Mention Setting the Valve Clearance. Did you Set the Clearance between the Valves and the Tappets? **Remove the Carburetor and the Crankcase Breather/Vent (# 8-1) and the Valve (Stem) Cover (# 8-2) 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 .004in - .006in and Exhaust .007in - .009in. 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 .004in - .006in and the Exhaust is .007in - .009in. 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. Once the Valve Clearances are Reached, 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.** What was the Piston Ring End Gap? Was it Less than .030in? 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. Thanks.
Respectfully
John
