Craftsman mower - starting problem

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  #1  
Old 08-12-04, 05:48 PM
powerman
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Exclamation Craftsman mower - starting problem

My lawn mower is about 4 yrs old. Its a Craftsman Model: 917.377991; Engine: Tecumseh 143.996704. I had difficulty starting it. Once started..I had to hold the primer bulb pressed to keep it running. I replaced the plastic bowl kit - 730637A and also the primer bulb. Even after replacement it does not start right away. If I prime it, the starter rope is slightly hard to pull. I end up trying to start a few times, let the mower sit for about 5 mins and then try again. This process continues at times upto 60 mins or so, with each attempt to start spaced about 4 - 5 mins apart. After a while it will start but will run for a few seconds and then stop. Pressing the primer bulb to keep it running does not help either. Again after a few 5 mins intervals, it will start running for a few more seconds. Finally it runs, but seems to have a lot of backfires or misfires and then the engine speed settles and runs smoothly. After this final start, I can stop the engine and can start it back up with one pull. Checked the fuel supply into the bowl kit. It seems to have no obstruction. Air filter and spark plug are about 2 months old. I had a technician do the tuneup at that time. I tried starting the mower with air filter removed. That does not help either. Any suggestions would be appreciated. Thanks.
 
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Old 08-13-04, 01:16 AM
cheese's Avatar
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Hello powerman!

Is the gas in the mower old? Will it start and run if you spray some carb cleaner into the carb throat?
 
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Old 08-13-04, 04:25 AM
powerman
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HI Cheese,

The gas is not old. I was able to use the mower this season, so had to replace the gas several times. I am not sure what a carb throat is. But I did take the air filter off and sprayed some carb cleaner into a couple of openings behind the filter, replaced the filter and then tried starting it. That did not seem to help either, unless I have to spray it liberally between each attempt to start.

Assuming the mower engine is not receiving enough gas to start and stay running, that seems to be an issue only during startup. Once I manage to start it and keep it running, the gas supply to the engine does not be seem to be an issue. Its almost like initially there is not enough pressure to keep the gas going to the engine, but once its running it manages to keep the supply on. Thanks.
 
  #4  
Old 08-13-04, 03:15 PM
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It sure sounds like a carburetor related issue but I also wonder if you have a valve train issue. When you serviced the carb with the bowl kit, did you soak the main body of the carb in a bath solution? If not, you may well have to do this. As for the valve issue, the best way to know is to perform a leak-down test of the combustion chamber, but most DIY'ers don't have the tools for this. Which means the only way to know if you do have a valve issue is to remove the cylinder head and valve cover and do a clearance check of the valves. Another problem you may have is with the brake assembly. These are notorious for not pulling far enough from the engine kill mechanism. To check this, simply use a pliers to help the brake to pull further and then check for running. Good luck and let us know.
 
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Old 08-13-04, 04:57 PM
powerman
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Hi Puey61,

When you say main part of the carb, is that the part that contains the Venturi, welch plug, throttle shutter etc. If so I have not cleaned that. I only replaced the primer bulb and plastic float bowl assembly. As for the valves, how does one go about measuring the clearance? I could probably get to the intake and exhaust valves by removing the cylinder head. If it is the brake assembly, should it not prevent the mower from starting all together? After repeated attempts, eventually I am able to start the mower.

Thanks.
 
  #6  
Old 08-13-04, 09:53 PM
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loosen lower carb bolt on bowl. gas should flow through bolt hole with ease. if not needle sticking in seat. one of my tecumsehs is bad about this. if flow is good to bowl. i would take off breather housing, look into center of carb, push primer and watch for gas to squirt on each prime through the center. gas should flow through center on each prime. if not suspect blocked ports or vacuum leak through primer or elsewhere causing lean condition and hard cold starts.
 
  #7  
Old 08-15-04, 02:05 AM
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I agree, it's beginning to sound like you may have valves that are too tight. If it is a flathead engine, there is a valve cover on the side of the engine behind the carburetor/intake area. It is a rectangular plate held on with 2 small screws. Put the engine on TDC and use a feeler guage to check the clearance between the tappet and the valve stem.
 
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