New to forum...D series problem...need help

[TJM_70]

I have a 19" D-series mower that I saved from a friends house. I've been a life-long Lawn Boy user and picked this one up for my wife to use...it's a 1976 5274.

It ran fine for the first few uses...but started to stall like it was starving for fuel a few days ago. I can start it and get it to run by hitting the primer, and keep it running if I increase the engine speed with my hand on the throttle...but it won't stay running on it's own.

I don't have diagnostic experience...I did the typical carb cleaning, new gas, air filter cleaning, spark plug.

I cleaned the exhaust ports a few years ago for my friend and I don't know how much it's been used since then...but I don't think this is an exhaust port issue?

Any tips or direction to search it out? Worn governor? Carb problem? Something simpler?

 

[Fireman 123]

You probably just need to completely disassemble the carb, thoroughly clean all passages, and make sure the float & needle aren't worn.

 

[TJM_70]

Any diagnostic tips to help me determine it IS in the carb?

If I need to do a rebuilt, I will...but I don't want to do it if I can't tell it's my problem.

 

[Fireman 123]

Any diagnostic tips to help me determine it IS in the carb?

If I need to do a rebuilt, I will...but I don't want to do it if I can't tell it's my problem.

You kinda described all the symptoms that would point me to the carb. It's a very common thing you have to do in order to keep any old lawn boy going. Very simple to fix, and parts are inexpensive.

 

[Rivets]

Fireman's got you on the right track. Rebuild the carb.

 

[robinb66]

You might also while rebuilding the Carb make sure to check the reeds, they should be flat against the plate sometimes they tend to gain space and quit working g as efficiantly seen it several time easily fixed by removing them and flipping them. There should be no clearance between them Ann's the mounting plate if there is.it should.not exceed 11 thousandths of an inch. You would be surprised at how.many I've worked on running the same.way and it was all on the Reed valves!!!

 

[TJM_70]

Thanks guys...I appreciate the advice. I suspected carb but it's nice to have some backup before tearing into something. I'm a good technician but a poor diagnostician.

My father is still using a 1972 19" to do the trimming every week at his house. When my brother and I were kids we mowed 30+ lawns a week with our two Lawn Boys - the 19" my dad uses and a 21" that has gone to the graveyard already.

I had a '96 Duraforce until the wife hit a rock while mowing and trashed it. I scrapped it and the cash from the junkyard bought went toward an early 80's 21" to replace the Duraforce. Craigslist - $50!

The 19" in this post was given to me by a friend who moved into a personal care home. The wife has her own vintage LB and seems to appreciate it. I'll post back once I have it running again.

 

[TJM_70]

Disassembled and cleaned the carb tonight...no improvement.

It will still start but the idle seems like it's too slow to keep it running. If I start it and just touch up the throttle an eighth of an inch, it runs strong and steady.

I tried to check the rpms tonight but couldn't get my automotive meter to work on the 1 cyl. Any way to do this?

If it was my chain saw, I'd adjust the idle up a little and go back to work.

Any other thoughts? How can I get the idle speed higher and what would be the cause of slow / low running speed?

 

[Fireman 123]

I'm assuming the hi / low speed knob is intact? It should be located below the rear side of the shroud / fuel tank. If it is, and functioning, the next thing I'd do is remove the flywheel, and check the governor assembly. I highly recommend finding an old lawn boy mechanic's handbook to help with this procedure as there's several parts to the gov assembly.

 

[Rivets]

Have you tried loosening the governor spring. You may have set it to tight when you rebuilt the carb.