Hello all

[Spiker1a]

I'm Steve
I'm a long time owner of a 1978 Lawn Boy 21" push mower. I received it 2nd hand in 1990 from my now ex mother in law who purchased it new.
It had no power when I first tried it and quickly discovered the exhaust port was almost completely plugged. I have used it almost exclusively until a couple years ago when I bought a new house with a larger yard and a John Deer Rider. Now I want to use it for trimming but it's running very poorly. I'm thinking the float may be fuel logged but still testing

 

[Spiker1a]

I believe I may have discovered the problem, the main jet seemed to be partially plugged. I'll have to test it tomorrow.

 

[Catherine]

Welcome to the forum, Steve!

:welcome:

I'm going to move your thread on over to the Lawn Boy section so you can keep us updated on your progress with that mower.

 

[ajwgator]

Hi Steve, just looking at your photo's of the carb & float it appears that the float is coated pretty heavy with something. If the stuff that is plugging your main jet looks like the same material that is covering the float, that is most likely where it came from. Most LB floats I have had experience with (only a couple) are cork and coated with a varnish covering. You can still see the cork material. Most fuels have ethanol mixed in them these days and this eats up the old varnish coatings on the cork floats and causes them to become fuel soaked and ends up not allowing the needle valve to close. The fuel will fill the bowl and keep running out the carb until the gas tank is empty.

Your float may have been painted with some type of paint. I have used epoxy to cover mine but it makes them a bit heavier so you have do a bit of adjusting. I recently purchased a pint of SIGSD105 SUPERCOAT CLEAR fuel proof paint from here Sig Mfg. Co., Inc. so I can do a better job next time.

Welcome to the forum.

 

[ajwgator]

Hi Steve, just looking at your photo's of the carb & float it appears that the float is coated pretty heavy with something. If the stuff that is plugging your main jet looks like the same material that is covering the float, that is most likely where it came from. Most LB floats I have had experience with (only a couple) are cork and coated with a varnish covering. You can still see the cork material. Most fuels have ethanol mixed in them these days and this eats up the old varnish coatings on the cork floats and causes them to become fuel soaked and ends up not allowing the needle valve to close. The fuel will fill the bowl and keep running out the carb until the gas tank is empty.

Your float may have been painted with some type of paint. I have used epoxy to cover mine but it makes them a bit heavier so you have do a bit of adjusting. I recently purchased a pint of SIGSD105 SUPERCOAT CLEAR fuel proof paint from here Sig Mfg. Co., Inc. so I can do a better job next time.

Welcome to the forum.

 

[Spiker1a]

Thinking back, I did coat the float with an adhesive sealant because I'd read about the problems with newer fuels.
I still had the same problem so I gave up for a long time as I had a full plate. I'll keep your theory about the plugged jet in mind.
I haven't had a chance to try out the carb yet. Thanks for the input.

 

[2smoked]

Hi Spike,

I noticed the label on the top of the shroud. I would disregard it and run it on 32:1. Just use a decent 2-stroke oil.

I have two mowers that use the early F engine like yours does. Lawn Boy had instructions on them that told you to run at 16:1 when using anything but Lawn Boy's oil. Forget that. You'll probably have less carbon too.

IMO, those F engines were Lawn Boy's best motor. I have had a 19 inch model like yours for 35 years and only had the motor apart to replace crank seals. Take care of them and they last a long time.

 

[Spiker1a]

Thanks for the info 2smoked, I would appreciate the reduced smoke.
I found the the coating I put on the float is indeed flaking off, I think the float is too deteriorated to use.
I've ordered a new float from amazon that looks correct. I'll check back in next week.

 

[Spiker1a]

New problem

I installed the new float, it does look like a perfect replacement. The bowl fills and shuts off so I know it's working.
The mower wouldn't start after priming and pulling a few times so I gave it a shot of starter fluid. It started the first pull and ran perfectly, for maybe 10 seconds and stopped. I tried again with the same result, only this time I was pushing the primer to try and keep it running but it didn't have any effect at all.
I can see fuel squirt into the carb when I press the primer bulb. I pulled the carb and checked that there is suction when I turn the engine over.
Any suggestions on where to look next?

 

[bertsmobile1]

replace the fuel.
If the mower will run continiously when you give it little blasts of starter fluid but wont run when you give it little squirts of gas, the gas is bad.
Double checking the carb is working by pulling it off and blowing air through it.
You should be able to see if not feel the gas coming out the engine side of the carb.
Works well for testing chain saw / leaf blower / trimmer carbs as well.
Needless to say, don't smoke while doing this, find a well ventelated area to do it preferably outside and away from things that go whoof when ignited.