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B&S 17.5 need valve work?


boutime's Avatar
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05-10-11, 08:31 AM   #1  
B&S 17.5 need valve work?

This might be lengthy but I want to give all the information first to try and find some help. First off, the engine is a 17.5 Hp Briggs and Stratton 31c707-0603-E1 on an MTD Yard Machine mower. I had to replace the steering shaft and so lifted the mower up to rest on its back end. Not able to break the screw loose I got the grinder and cut off the screw but also caught the mower on fire but just around the gas tank, and steering wheel, no damage to the engine. Now the problem, since I put it back together the mower will start but dies immediately, almost as if it runs out of gas. A few times it has started and I have been able to mow with it for 10 or 15 minutes and again it dies. So far I have replaced the carburetor, gas lines, gas filter, new air filters, fresh gas, new oil, and new plug, checked the gap on the armature, replaced the gas cap, and inspected the gas tank for damage. Gas flows freely through the lines when removed from the carb. If I take off the air filter and hold my hand over it to block all air I can keep it running by limiting the air flow into the carb, but it has to be very limited or it dies. It always starts easy but dies quickly. I wonder if it could be a head gasket or burnt valve and will tear into the next but really wanted to ask advice on anything else I might have overlooked. Before I tipped it up it ran great so I have to wonder what happened after I tipped it. I am at a loss and appreciate any advice on this.

 
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05-10-11, 11:42 PM   #2  
Blocking air to keep it running means it isn't getting enough fuel. When you remove the fuel bowl on the carb, does gas flow into the bowl area freely or is it just a dribble? You said you replaced the carb. A new carb or one off of another mower, or...?


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boutime's Avatar
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05-11-11, 11:05 AM   #3  
The carb is brand new complete with the solenoid. It was suggested I check the voltage of the solenoid as the wire may have been damaged due to the fire. Going to check into that this evening after work. As to the gas flow it if free as I checked into tht wondering if there was a problem with the float or needle. However it runs the same with the new carb as it did with the old.

 
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05-11-11, 06:31 PM   #4  
I'd want to take a look at the power to the solenoid. The lead comes from the ignition switch so I'm thinking that tilting it back or the fire (trying not to laugh here) may have damaged some insulation somewhere or the connection is intermittent.

 
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