old lawnmower service?

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May 6, 2014
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i got an old flymo lawnmower from my brother it uses a briggs and stratton engine, its not been used for over a year so was wondering what i can do to service it. i dont have the owners manual for it any more so dont know what so of oil i can put in it. also it doesnt seem to have a oil drain plug so not sure if im supposed to suck the old oil out or not?
i tried to start it but didnt fire up, iv put fuel in it and gave it 4 pulls on the cord. it spins freely but didnt fire up, dont know if i just got to keep giving it more pulls or something. my chainsaw has a on off button but i cant see on on the lawn mower.

IMG_20200624_101302.jpg
 
Oil is typically drained through the fill port by tipping the mower on it's side.
I prefer to perform this operation when warm/hot - and immediately after running out of petrol.

Berryman's B12 is a popular fuel varnish solvent/cleaning agent - it is basically Acetone, Lacquer thinner, & Methanol.

The safety brake band that wraps around the flywheel needs to be adjusted properly -
as does the interconnect to the ignition kill switch (it is integrated) - it is a very thin black wire.
 
Carburetors are almost always the issue for mowers that have been sitting. You can clean with Berryman's, as Linctex mentions, or other carb cleaners. You may need to take the bowl off, too, and clean it out.
 
Did a service on mine.... That one is basic L-head 3.5 hp classic... 3.75 hp.... 4hp engine...

Carb membrains p/n #795083

O-ring on maniford p/n #270344s

Sparkplug: champion rj19lm.... Ngk br2lm... Denso w9lmrus...
 
i think the engine should have around 10 hours of run time maybe less in total. i switched over to a manual push mower for a few years so i think this lawn mower has been sitting for atleast 2 years in the garage unused.
will try and fire it up later today.
 
Definintely sounds to likely be a carb issue. Was it stored with fuel in it or dry? I'd strongly consider replacing the spark plug and air filter while you are messing around as they are pretty inexpensive and can avoid extra headaches later. I recently purchased a low hours Husqvarna mower that everything checked out, just needed a new coil for some reason and then oldly the kill switch cable housing was gummed up so I replaced that as it wasn't letting the safety bar pull the kill switch far enough. I was pretty surprised about that- they actually used compressionless housing which was poking through the plastic end ferrules.
 
My SOP , each spring is check air filter , change oil , drain gas , refill with pure gas and install a new spark plug .
 
Make sure there is oil. You can worry about changing the oil later. Take the air cleaner off (big flat-head screw on top) and drop about 1/2 teaspoon of gas into the intake. Pull cord and see if it fires at all. The "deadman" bail on the handlebar needs to be held down for the engine to start or run. Usually the starter cord is extended up to the handle so it can be started while standing behind the mower and holding the handlebar.

If it runs for a few seconds (burning the gas you put in) then stops there's a fuel problem. If it doesn't fire at all you'd go on to check the ignition system. Almost always it is a fuel problem though.

It is a diaphragm type carbuerator. Do not put B-12 or other solvent in the gas tank expecting a miracle, it's just going to ruin the rubber. You'd have to tear down and clean it. The big problems are dirt and/or water in the tank or bowl, the rubber diaphragm hardening, and the main jet (well, the only jet) being clogged. The jet is under the tubular screen on the bottom.

To disassemble carb remove the tank / carb assembly from the engine then take out the 4 or 5 screws holding the carb body to the top of the tank. Note that most of the parts are plastic, so be careful not to break them.
 
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^ Covered above about how to diagnose and the membrane part number 795083, which should cost less than $4. Another way to confirm the presence of spark and compression is to squirt Starting Fluid into the air intake after the air filter is removed. It should run for a short while if you have spark and compression and then you know it is time to rebuild the carb. Carb rebuild on this is simple.
 
Its working!
2 pushes of the red button got fuel in and it fired right up.
Oil was on lower mark of dipstick so topped it up. Oil looked very clean on the paper towel.
Will cut grass tomorrow then look to change air filter spark plug and oil
 
Originally Posted by WyrTwister
My SOP , each spring is check air filter , change oil , drain gas , refill with pure gas and install a new spark plug .



You are much better off draining the gas at the end of the season. When everything is dry there isn't a chance for it to cause issues.
 
what oils best for these engines? says to use sae30 or in colder climates to use 5w30 and if used for prolonged periods of time like commercial grass cutting to use 15w50.
so thats a large range. would i be safe with something like synthetic 5w40?
 
Straight 30 Weight oil will work, but most use 10W-40/15W-40 oil.
Synthetic oil is great too.
I prefer a 40 weight oil in air cooled equipment.

My 2¢
 
Originally Posted by jeepman3071
Originally Posted by WyrTwister
My SOP , each spring is check air filter , change oil , drain gas , refill with pure gas and install a new spark plug .



You are much better off draining the gas at the end of the season. When everything is dry there isn't a chance for it to cause issues.

Or let it run untill it runs out of gas . To empty the carb .
 
Originally Posted by slybunda
what oils best for these engines? says to use sae30 or in colder climates to use 5w30 and if used for prolonged periods of time like commercial grass cutting to use 15w50.
so thats a large range. would i be safe with something like synthetic 5w40?



There is a large range because pretty much anything within the range would be safe, as small engines are more picky about the oil level being full than what actually goes into the crankcase. Like stated in the manual, it's more dependent on climate and usage. A good HDEO like Rotella 15w40, 5w40, or 10w30 will literally cover all the bases which is why it's a popular choice.
 
Ahh thats handy. I got left over 5w30 and 5w40 from the cars is mixing oil ok?
 
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