Old engine not running, Craftsman brush trimmer

[pripyat]

My wife's grandfather died, he was a small engine mechanic, has worked on tractors since the 60s. I was told to get whatever I wanted out his shop and wound up getting a wheeled string trimmer. This is something he was working on for a customer, either it was never picked up or he was having a hard time fixing it. I pulled the carb and cleaned it, the engine starts first pull, every single time. The engine comes up to speed and then immediately shuts off. After it comes to a complete stop I pull the starter once and it does the same thing again - Starts beautifully then stops. I can overcome the governor linkage on the carb with my hand and keep the engine running by manipulating the butterfly valve. Interestingly there is a throttle cable assembly installed on the unit but I don't believe it goes to this piece of equipment. When I got the trimmer, the throttle adjustment was present on the push-handle but the cable was just hanging. He may have been trying to run the engine without the governor, directly connected to the throttle? Or possibly I am wrong and there is something else going on entirely. Can anyone point me in a direction?

Numbers off engine shield - 143294032 SER-9032E

Numbers off trimmer unit - 536.7735100 Code: 9112062922







Any help is appreciated. Thanks!

 

[RandyT]

Symptoms lead to not getting fuel after the initial prime. Sounds like a carb problem, Could be related to the bolt nut/jet. The other issues are you have a primer carb on an engine with a housing that says automatic choke. so we either have an engine that somebody has changed the blower housing which could cause issues having the incorrect model number for the engine, or somebody has put a primer carb on an engine that originally had a choke and possibly wrong carb jet size. I know the air filter isn't original to the engine. Also with the governor spring tab bent so far to stretch the spring makes me think there could be other issues as well.

 

[pripyat]

Thanks a lot for that reply. The main jet in the carb is massive compared to the other small engines I have around the garage. I used a set of welding tip cleaners in the carb ports, the main jet took the second to largest.

Any suggestions on where I should start? I'm assuming compression is good since it starts up so quickly. I can do a compression test if that would be helpful and report back. Would a video of what the governor is doing be helpful?

 

[Roadworthy]

As a last resort, I've had good luck sourcing new carburetors on eBay. With the engine number you can come up with an original factory carburetor for a surprising number of things.

 

[RandyT]

I don't remember the main jet in the nut being that big. I seem to remember that it is somewhat large as it enters the nut from the carb side, but tapers down considerable as it gets close to the bottom of the nut. Can you blow carb cleaner through the passages in the nut from both directions.

 

[pripyat]

My terminology may be off. I was referring to the diameter of the pickup tube or venturi being large. The orifice in the nut and the two orifices on the carb body piece it screws into are wide open.

 

[/pine]

Have you checked the float valve and the seat??
I too would search e-bay for a new carb parts...

 

[pripyat]

So I went out to make a video of the carb linkage. Each time I started the engine it would run a little longer before shutting off. After 4 or 5 tries it just kept running. I know nothing about these engines, I'm guessing I should manually pump the bulb to keep it running when cold? Manual choke LOL

BTW, I did check the float. I basically just made sure it was letting fuel in and wasn't overflowing into the intake when the fuel level in the tank exceeded the intake height.

I did a compression check, after 4 pulls it was up to 120psi. I'm interested now to see if I can lean the engine out a little, the plug looked really bad, dark black with lots of carbon deposit. I've got a tiny drill bit set specifically for jets, I'm assuming I can just JB weld the previous orifice and drill a new one a size smaller the same height up the bolt? Is this advisable or should I leave it alone?

I went ahead and pulled the oil drain, the oil looks and smells ancient. Going to run some full synthetic in it for a couple hours then change it again. Hoping to get a lot more years out of this little engine.

Any other advice as far as maintenance to keep this thing going for a long time to come? I'm assuming valve lash wouldn't be a bad idea..

 

[denchen]

There is usually a long, not very strong spring on the throttle butterfly, that keeps the engine running at full speed. Once up to speed, the throttle `flap` under the casing then pulls the throttle butter fly closed so slowing the engine. I carn`t see this spring on your pictures. As the engine slows, the wind pressure decreases on the flap and the spring open the throttle a bit further. What then happens is the engine settles down to its normal running speed. To control this speed, another spring is attached to the linkage and the wire speed control. By increasing the tension of this second spring, putting more pressure against throttle flap, and the engine will then run faster.

 

[pripyat]

Thanks for that reply, I am having a hard time finding a resource online that explains how the governor works. At this point it seems that the upper half of the unit is off some other piece of equipment as the engagement lever across the handle and the throttle cable is totally useless and unused.

Thanks for the input about the spring - So there should be a spring that holds the throttle open that the governor has to overcome?

I drained the oil, it was the worst I've ever seen. I let it drain for an hour and then replaced it with new oil. I ran the machine but I couldn't engage the trimmer portion without the engine dying out. I found that if I put my finger over the hole on the primer bulb, the engine rpms increased. I put tape over the primer bulb and was able to trim some weeds. I let the engine run for around 10 minutes then drained the oil again.



Sadly the second drain is pretty bad, too. The drain plug was covered in sediment, I imagine that after a couple hours of running I'll change it one more time.