Dear Ole Mechanic;

Gasoline GeneratorI just bought an old gasoline powered generator at a local auction.  When I say old, I mean OLD.  I over heard a fellow talking about it before the auction started.  He said that because the spark plug was in the side of the head instead of in the top of the head, it meant that the engine was made prior to 1940 because that was when Briggs changed the spark plug to the top.  After I got the generator home, I cleaned the brass plate on the side of the engine and I found that the engine is in fact a Briggs & Stratton Model A, so I am inclined to believe what he said.

Once I got some time to tinker with the engine, I followed your advice.  I checked for oil in the crankcase, spark, compression and fuel.  It had oil.  With the spark plug out and grounded, I gave the engine a crank and got a nice blue spark.  With the plug back in, there seemed to be good compression when I cranked it again.  I did get a new fuel shutoff valve with a sediment bowl and checked the fuel tan--which was clean.  I checked the carburetor--which was also clean--so I put gas in the tank.  After a little cranking, popping and adjusting the carburetor, it fired up and ran.  Then came the problem.  The governor was not working.  After I shut off the engine, I found that the governor shaft coming out of the side of the engine is locked up solid,and there is no way to control the engine speed.  At that point, I knew that I was about to get in over my head, so I stopped.

Should I start trying to wiggle the shaft, or will that just tear up things?  What drives the governor?  How completely am I going to need to disassemble the engine to get to the governor?  I need HELP.

Tinkering

 

Dear Tinkering;

It is better that you gave me all of the information that you had rather than leaving me without enough info to help you.  Wiggle the shaft gently while applying penetrating oil.  If gentle wiggling doesn’t free up the shaft, then there are no two ways about it, you are going to have to open up the engine.  First, a little of the information you wanted.  There is a gear on the crankshaft that drives the camshaft.  The gear that drives the governor may either be driven off of the crank gear or the cam gear, because my reference book is not clear on exactly which one drives the governor.  The governor consists of a pair of spring-loaded fly weights that are hooked to and move a sleeve back and forth, depending upon engine speed.  The shaft that comes out of the engine contacts the sleeve inside of the engine and moves the carburetor rod outside of the engine to open or close the throttle as needed to maintain the engine at the correct speed to run the generator.

OK, so much for what should happen.  Now, how to get to the governor.  I would suggest draining the oil out of the crankcase and removing the crankcase extension from the bottom of the engine.  This will allow you to inspect the governor and shaft from the bottom.  Look for the correct positioning between the sleeve and shaft, as it may just take a little pressure to move the shaft or sleeve into its correct position to get things free and working again.  Should you spot a more serious concern like a bent or broken fly weight pivot shaft, then a more complete disassembly will be needed.  You will need to remove the flywheel cover, the flywheel (puller required), the crankshaft main support plate with magneto and possibly the camshaft--which will require holding the valve tappets in the open position.  If you do not have experience at disassembling small engines, I would suggest getting a service manual on the Briggs & Stratton Model A Engine or getting assistance from someone who does have experience working on small engines.  Better yet would be both the manual and someone experienced enough to explain things and--before you ask--sorry, but I am busy.

Oh, you may wonder how I knew that the engine had a crankcase extension and not a simple cover plate.  I was at the auction with a friend who was bidding against you.  Congratulations on your $27.50 purchase.  By the way, my reference book dates the engine sometime after World War II and before the mid 1950’s. 

Herr Professor Nuzanbolts




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