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Well I purchased a 1981 LawnBoy 4502 to use as a weekly mower. I fell in love with this style LawnBoy when I was young because my father and grandfather both owned LawnBoy Scamps and I mowed countless yards with those mowers.

Anyways, after I purchased my 4502 I replaced the spark plug and air filter, put in new gas, and have been using it ever since.

The last few times I have mowed it has started surging as if someone is turning the ignition "on" and "off" at about one second intervals. Today it started to die intermittently and became difficult to start.

I decided to take the top cover off and check things out. The gas lines need replaced and the carburetor is beyond filthy both outside and in the float bowl. The gasket between the carb and the cylinder is in terrible condition and fell apart when I removed the carb. The coil pack also looks a bit worse for wear. This mower definitely has some "acres" on it. Ha!

Anyways, I am new to lawn mower mechanics and have never really messed with carbs. What do I need to look for and make sure is clean inside the carb? Also, can I soak this plastic carb in some sort of parts solvent? I don't want to damage the plastic.

Are replacement carb gaskets and carb base gaskets still available? If so where can I source them. Also, is there any kind of maintenance I should do to the coil like setting a gap or cleaning the surface where it meets the flywheel? Should I just replace the coil as preventative maintenance and if so where can I locate one?

Sorry for all the questions. I have searched online and haven't found much about this mower specifically.

Any help is appreciated!

Nice looking machine! My best suggestion to help with all your issues/maintenance would be to find yourself a mechanic's handbook. Yours is an F series engine. Yes, many parts are available, and eBay is a good source. Go to Lawnboy.com and enter your model number to find parts diagrams.

I'll bet the problem is in the fuel system (clogged carb, etc.) I wouldn't change anything on the ignition system until the fuel system has been cleaned up and fitted with new gaskets. You can use solvents on the plastic carb parts -- no problem.

Check out this page on Lawn-Boy's website. It has links to many manuals for free download, including one about the F-series carb.

I fully cleaned and reassembled the carb last night. The engine is still surging even though the float, needle and seat, and jet are clean as a whistle. I also removed the altitude adjustment screw and needle and cleaned it.

The motor now seems incredibly hard to start. It was a bit difficult to start before. Sometimes if I play with the kill switch by putting it in the "middle" position (between on and off) and pull the starter rope, it will act like it will start, then start after placing it back to the "on" position.

Could I have a bad kill switch? When it is hard starting it is getting fuel but acts like the plug isn't firing at all. Symptoms tend to get worse after the engine is warm which is one of the reasons I think the coil could be problematic.

I went ahead and ordered a new needle and seat for the carb just to rule that out since it is so cheap.

scrible said:

I fully cleaned and reassembled the carb last night. The engine is still surging even though the float, needle and seat, and jet are clean as a whistle. I also removed the altitude adjustment screw and needle and cleaned it.

The motor now seems incredibly hard to start. It was a bit difficult to start before. Sometimes if I play with the kill switch by putting it in the "middle" position (between on and off) and pull the starter rope, it will act like it will start, then start after placing it back to the "on" position.

Could I have a bad kill switch? When it is hard starting it is getting fuel but acts like the plug isn't firing at all. Symptoms tend to get worse after the engine is warm which is one of the reasons I think the coil could be problematic.

I went ahead and ordered a new needle and seat for the carb just to rule that out since it is so cheap.

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How did you make out on this? I like that mower. Does it come with the steel deck?

Rudedog said:

How did you make out on this? I like that mower. Does it come with the steel deck?

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Yep its a steel deck.

See this thread for more info: New (to me) 1981 LawnBoy 4502... lots of questions! - MyTractorForum.com - The Friendliest Tractor Forum and Best Place for Tractor Information

:biggrin:

you might want to check and clean the exhaust ports.

I got it figured out, exhaust ports are clear. See the thread I posted from My Tractor Forum. There is a great group of Lawn Boy guys over there.

Two-Stroke said:

I'll bet the problem is in the fuel system (clogged carb, etc.) I wouldn't change anything on the ignition system until the fuel system has been cleaned up and fitted with new gaskets. You can use solvents on the plastic carb parts -- no problem.

Check out this page on Lawn-Boy's website. It has links to many manuals for free download, including one about the F-series carb.

Click to expand...

If these are 2 stroke engines, (oil/gas fuel mixture) The exhaust can get plugged with carbon deposits. If muffler comes off then clean it out by scraping carbon off. I had the last model 2 stroker sears offered, for a few years. Pretty much identical to the old Wizzard from Western Auto. My muffler was plugged up and it was powerless. I got out my drill and went after the outlet ports in the muffler. Holy Cow now the thing ran like a CHAINSAW ! Amazing. I was lovin it . . . .for about half an hour when the piston rod exited through the side of the crankcase. I must have unwittingly took off a few thousandths from the holes and let the engine breathe easier. My Bad, turned out to be real bad for that mower. Dont remember it surging before i worked on it though.

I sure do like the old Lawn Boys... When you passed in front of somebody's house that was cutting grass it smelled so good........

I remember when Briggs and Stratton Kopy Katted the starter system from Lawn Boy... The straight up style system.... They had a young lady doing the ads on TV..... "If she can start it anybody can"... I think that was the slogan they used...

Well that system didn't go over well. Too much compression on a 4 stroker than a 2 stroker I think was the issue... I have 2 of the upright starter Briggs engines made back in the day with the cam shaft sprocket sticking out for the rear wheel drive self propelled models..... Future projects to get running if I can find some frames to match......

Great mowers like they used to build as they say ...........

Plus Tard Mes Amies ~!~!