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Discussion Starter · #1 ·
Greetings,

I'm trying to help my father repair his lawnmower, a Craftsman 21" high-wheel push mower with a 625 series Briggs & Stratton engine (4-cycle). The mower is Sears catalog # 917.388114. The manual & engine info is here: click

Hopefully we can save this one from the graveyard as cheaply as possible. I'd appreciate your advice on what things to do.

The problem is that the mower doesn't stay running. Dad says it'll start, but then the engine stops shortly after starting. The spark plug was replaced sometime last year, but unfortunately (please don't shoot the messenger) it's never had an oil change and he keeps old fuel in the mower, even over winter. I'm pretty sure the engine is need of a good cleanout, but I'm not sure what/how to do it.

My thoughts on things to try:
  • change oil
  • dump fuel tank
  • change fuel filter
  • change air filter
  • inspect & possibly change muffler (?)
  • pull spark plug & crank motor to clear out cylinder

Are there other things I've missed or worth trying? I'm particularly interested in methods for cleaning out the fuel system and carburetor components. Is there maybe an additive that I can put in the tank to do the job, or does it require disassembly?

Do you think this thing is gummed up beyond hope?

Thanks!!
 

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Discussion Starter · #2 ·
Oh, also, if I wanted to pressure test the cylinder, does anyone know what the spec is?

I have an automotive cylinder pressure gauge. There should be a fitting to fit the spark plug hole on the mower (hopefully). However, I don't know what to do about the oil/fuel... don't want to bugger up my gauge.
 

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change oil Yes
dump fuel tank Yes
change fuel filter Yes
change air filter Yes
inspect & possibly change muffler (?) Inspect OK Changing probably not necessary and very expensive in some cases.
pull spark plug & crank motor to clear out cylinder Change plug. Only thing to clear would be fuel if it is flooded but nothing to clear short of removing the head to de-carbon the head, piston and valves which may not be necessary at this point

I think the main thing to concentrate on would be to get the fuel system in order. Clean out tank, check or replace fuel lines if any signs of being hard or weather checked (Dry Rotted), replace in-line fuel filter and rebuild the carb. You'll probably have to clean it out so you might as well re-build it with new gaskets and seals.

Do this first and you may not have to go any further and this would need to be done to accurately diagnose other issues.

Seafoam would be a good additive to put in your fuel if you have a little dirty fuel issue but sounds like this one might need a little more attention. ;)
 

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:ditto:Sounds like all you need is some general cleaning and maintenance. Often, with dirty fuel with corrosive ethanol in it, the fuel system will get pretty gummed up. Usually, a carb rebuild and cleaning will remove the varnish and solve the problem.
 

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Discussion Starter · #5 ·
Thank you both.

As I've never done it before, is there a procedure posted here for rebuilding the carb? I'm assuming that if I walk into a local Sears service center they'll be able to get me the parts needed.
 

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It's not hard to rebuild the carburetor. You just take it apart, clean the metal components with carb cleaner(be sure to keep the cleaner away from plastic or rubber), and replace the parts that come with the kit. If you want, there are many youtube videos about carb rebuilds to watch. As to parts, you'd probably be better off going to a local engine repair shop and ordering the kit. Sears is not known for stocking parts. You'll need the B&S model/type/code numbers stamped onto the metal engine shroud.(some of them have it on the front of the engine under the plastic shroud, and some have it on a plate on the side of the engine)
 

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Discussion Starter · #8 ·
Got the mower running again! I didn't see a fuel filter on this particular model. The fuel line from the tank ran straight to the carb, so I just cleaned out the carb. Also changed the oil, air filter, and spark plug. Used fresh fuel with stabilizer. It ran a little rough for a couple minutes and had some smoke but it settled down and the smoke went away.

Only thing left is to change the throttle control cable because it's worn and not giving enough tension to keep it running. Had to pull on the cable to start it.

Thanks for your help!
 

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Discussion Starter · #11 ·
So I think I might have introduced a fuel leak somewhere when I was working on the mower. I won't get a chance to go over my dad's house for a couple days to look at it, but apparently now it leaks fuel when the mower is tipped over or forward.

I suspect that there's a leak in the carb, maybe a bad gasket? Just wanted to get some ideas about where fuel could be leaking from besides the tank and the fuel line going to the carb. Thanks again!
 

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Do you mean that the engine leaks when the mower is on its side or upside down? A lot of mowers will leak anyway, cause the gas caps are rarely that great.
 

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gas...carb problems

I notice that the gas now days (as you all know) is bad for all small engine's..in year's past you had a 75% chance that your lawn mower's would start up next spring when you put it up for the winter...BUT now days I've notice that if the gas is left in your mower's for more than 30 days you have a great chance of it not starting or running rough...as a mechanic for 40+ years i'm telling you that a real light film hardens in the carb's jets...and float..so gas can't flow...this is a gravity flow, so no pressure on fuel flow. most of the time just take the carb apart and blow it off with air and down the carb throat will fix the problem.....hope this help every-one:2th:
 

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Discussion Starter · #14 ·
motorhead12, you were exactly right... the gas cap is allowing fuel to flow out when the mower is tipped. I guess it's nothing to worry about, but makes me wonder what the point of the gas cap is.

Amity Pete, thanks for the tip!
 
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