QuestionI am working on a B&S 3.5 HP motor - Model 92908 Type 5071-01. I originally purchased this motor new around 1985. Has "Pulsa jet"? carb I believe. Motor quit while mowing, had been working fine. Began working on it; was able to get motor running at slow speed but would not accellerate to working speed. As the motor had been sitting for 15+ years before I revived it recently (started on 4th pull and lasted me through 8 months of mowing until recent issues)
I have just finished replacing the rubber diaphragm/gasket between the tank and the carburetor - which among other things apparently serves as an automatic choke - on the assumption that the gas-drawing capability of the old one had been compromised due to age, etc. Made sure to install as per instuctions with choke plate positioned to pre-tension the diaphragm.
Mower now starts quite readily on slow speed (previously would start at any speed, usually full speed) and will run for 2-3 min easily, on very gently throttling up it will sometimes gain a little bit of speed before slowing and stopping. Quick throttle means immediate stall. I can usually re-start it right away with one mild pull. While running with air cleaner removed, as motor begins to slow down (getting ready to stall) I can begin to see smoke (I think it's exhaust, smells more like that than fresh gas, though hard to be certain) coming out of the carburetor where the air cleaner goes; smoke increases as engine slows & runs rougher, then stalls. Do I have a bent valve or something?
Thoughts? Thanks!
AnswerHello Jonathan:
From your Description it Sounds like the Valve Clearance May Require Resetting. 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 .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.** 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
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Respectfully
John
