4502 Runs a short while and dies

Guys, I have a Lawn Boy 4502 with the F300 series engine, and a white plastic carburetor.

The engine will start usually within one or two pulls after priming (3 or 4 pushes on the primer bulb). Then I can cut the grass for about five or six minutes and then the engine begins to act as if it is running out of fuel - rpms rise and fall and then the mower will cut off.

I can prime it and sometimes it will restart, other times it will not. The float was replaced a while back, along with the float needle and valve. Also the fuel line was replaced and since the shut-off valve on the tank has a broken handle, I installed a HAK cut off valve.

I seem to remember it having this problem years ago, before I replaced the float, needle, and valve. I set the float level per the factory setting in the on-line manual: https://lookup3.toro.com/ttcGateway/...als/lball.html

I am using a 32:1 fuel mix and the engine doesn't seem to be running hot as sometimes after I get it to restart it will run for 30 or 45 minutes so I can finish the yard.

I have also replaced the coil (today) and are still having the same exact problem.

Thoughts?

Verify that gas cap is vented and operational (not blocked or clogged).

Well, I switched gas caps and it seemed to help. So, I took out the black liner inside the gas cap and found a piece of something that was bouncing around in-between the vent hole and the black liner. It must have bounced up and clogged the vent hole every so often and that caused the shut down. I removed the debris and it runs fine now.

Thanks for the tip!

Good job Russ.

and what is crazy is I followed the Trouble Shooting procedure:

https://lookup3.toro.com/ttcGateway/...ls/lball16.pdf

and I checked the vent hole in the gas cap (visual from the outside) and it wasn't restricted - who would have thought a piece of the inside of the cap itself could detach and bounce around enough to clog the vent hole.

LawnBoy4502 said:

Well, I switched gas caps and it seemed to help. So, I took out the black liner inside the gas cap and found a piece of something that was bouncing around in-between the vent hole and the black liner. It must have bounced up and clogged the vent hole every so often and that caused the shut down. I removed the debris and it runs fine now.

Thanks for the tip!

Click to expand...

It’s no secret that I am a fan of vintage Lawn Boys. And one of the things that I like about them is that, problems with starting or running are most often caused by a small issue that is easily solved. Persistence and patience helps, along with thinking through the problem. It also helps that older Lawn Boys have a simple, no fancy frills design. It’s no wonder you still see some out there that are over 40 years old cutting away like the day they were purchased.

Just the other day, I had to dispose of something on the local scrap metal pile and couldn’t help but notice a brand X mower thrown on the heap. It looked to be very new-no more than three years old. What an example of our wasteful, throw-away society. On the way home, I couldn’t help but notice a homeowner cutting his grass with a nice looking old Lawn Boy that I know was at least 45 years old. I also noticed that he also had an early F engine model in the garage and I’ll bet it was a runner too.

My compliments to you for keeping yours up and running.

Thanks, I am a big fan of Lawn-Boys. I have two of them, both from the early 80's and they are now both working great! With both of them being over 37 years old, I get strange looks from my kids because I won't replace them with newer mowers.

I love the light weight of them both - easy to push and work the yard with. And to me, they are worth keeping as opposed to scrapping them out. No point in throwing away good equipment that does the job.

And honestly, I really enjoy the "peace" I get when I'm working on one of them - it's almost therapeutic.

LawnBoy4502 said:

Thanks, I am a big fan of Lawn-Boys. I have two of them, both from the early 80's and they are now both working great! With both of them being over 37 years old, I get strange looks from my kids because I won't replace them with newer mowers.

I love the light weight of them both - easy to push and work the yard with. And to me, they are worth keeping as opposed to scrapping them out. No point in throwing away good equipment that does the job.

And honestly, I really enjoy the "peace" I get when I'm working on one of them - it's almost therapeutic.

Click to expand...

It’s not “almost” therapeautic. It IS therapeautic! You must be my twin.

Well said. You would not believe the looks I get. It's a Briggs engine but still a lawn boy to me. What I am so amazed and thankful is the amount of knowledge offered on this site and the men and women that provide it from all over the world. I cherish it.