Well howdy folks. First time posting here, but been a lurker without an account for a few months now..

I have run into an issue! I received a push mower from a co-worker that was a "POS that never ran right" according to him... and so far I am agreeing! Long story short the mower refuses to run correctly and I am at a loss to what is wrong.

Below are the details:

Equipment Type: Push mower
Name brand of motor: Briggs and Stratton 450E Series
Model Number: 08P502/0047-F1 / 150CC
Issue: Sputtering/Backfiring, Smoking out of Filter/Carb area, Dying while running

Attempted solutions and thoughts.. At first I figured this was a simple gummed up carb, new filter and spark plug job.. So this is where it all started:

• Sponge filter was cleaned, dried out in the sun, fresh small amount of oil added to it per manual and reapplied.
• Checked old spark plug, which was still in good shape so reused for now.
• Drained the old gas, grabbed a higher octane gas and refueled.
• I ran some seafoam through the carb, blew it out with compressed air, and made sure all connected parts where free from debris.
• I emptied the gas, re-blew out the carb, fresh gas again.
• Performed an oil change after hot soaking the motor to make sure the oil was clean.
• Took the head gasket off to find the gasket seal was cracked (Co-Worker cracked when replacing spark plug.. he for some reason took the whole head off... ), so replaced that and cleaned up carbon deposits while in there.
• Purchased and Changed spark plug with proper gap. (.20 I believe)

All of this, for it to run as bad, if not worse! So again.. I am lost. I have went to the liberty of recording the mower for y'all to hear what is going on.... (If this is not allowed please remove link!)

FAIR WARNING THE VIDEO IS LOUD!!
Youtube: https://youtu.be/eKSAgKKu6I0

Any help you can all give me, would be fantastic. I would love to get this working as besides the repairs it has been free!

 

Check to be sure the zone cable is completely pulling the on/off switch. Sometimes if they stretch, they make intermittent weak contact and cause erratic running. Also make sure the o-ring is in place where the carb seals against the intake.

Thank you for providing full details in advance!

 

Cheese! Thanks for answering first.. Second, Its no issue to include details when asking for help.. saves time and effort

Onto the mower! I did a quick measure on the Zone cable where it connects to the motor.. Handle "clutch" decompressed its about 2 inches long at the motor. Compressed it is about 1 inch long. I am not sure what the standard is, does this sound about right?

As for the O-Rings, the ones that connect from carb to head, are a hard plastic O-Ring, and even when pushing hard on the carb towards the head, it still sputters.. I checked them for cracks and such and did not see anything.. I will double check though.

Edit: I checked the wire from the ignition coil back to the on/off switch... everything SEEMS in order there. The wire is undamaged, and free of debris on both sides of the connection.

You can see how I am stumped here

 

Inside that hard plastic should be a soft rubber o-ring.
Are you sure you have the auto choke correctly hooked up?

 

Howdy BFHFixit,

As far as I know all of the O-Rings where good in/on the carb. I checked all of them and noticed no deterioration on them. After a double check, all still seems in order.. I even pulled the hard rubber and soft rubber out of the carb and resealed them.

As for the auto choke, I *believe* this is still correctly hooked up. I took as much care as I could to not stretch out the tension spring, and made sure the control arm was re attached at both sides (never came off one side, only on the carb side)..

Today, after sitting over night the mower doesn't even want to stay on. It has half a tank of gas, starts up, runs alright.. then shuts back off.. The only thing Ive done is remove the carb, put it back on (without shaking or spilling any gas around) and reattach the pull rope.

 

This is the one I believe cheese was referring to and I was.

 

On page 4 of this IPL, should be your carb. The o-ring I thought cheese mentioned and I was confirming is 724 which is surrounded by 617-623 which is plastic.

These carbs IMO are pure junk, we have a rental push mower that will plug with everything being proper simply sitting for a day or two. Have another return as the customer had the same problem.

From your video it sound to me like it is running rich and with that carb, would mean the fuel transfer (117 on the drawing) is the problem or associated o-rings.

I am as cheese is, thinking it is a carb issue and one you may not resolve other than replacing. These things are all cheap plastic depending on tiny o-rings to work.

Absolutely no offense to you but since my volunteered time here is often derailed by mods of other forums on this site, I can not contact Briggs on your behalf however, I would suggest if you still have problems, that you do so...they do have an Excellent customer support.
https://www.briggsandstratton.com/na/en_us/support.html

 

Edit: Interesting topic. I was debating replacing the carb and seeing if that fixed the issue.. The strange part about this is; I have soaked this carb part by part in MMO, then blew compressed air through it verifying every port is unblocked (Not to say it isn't still lol)

So in your opinion, Replace the carb and see if that solves the issue next?

 

I would say yes. If any of those tiny o-rings are not sealing properly, the fuel is not routed through the jets correctly and properly vaporized which results in a rich condition evident by sputtering and then the backfiring as un-burnt fuel passes through the cylinder and into the hot muffler igniting.
As I said from your video, that is what it sound like to me and I have found many carbs that are using this type of plastic fuel transfer, Nikki carbs are terrible as well. I gave up kitting them also as my success was a mere 25%.
MMO is not a carb cleaner, the basic spray cleaner you get at wally world or any parts store is all I would use on these plastic junk.....the big thing is the o-rings though...if they don't seal right, your done.

 

I have used MMO, and seafoam directly into the carb, as well as generic carb cleaner spray. To no avail. So I believe my next step is to get my hands on a car and throw it on there.

It will probably be a few days before I can get one, however I WILL post back once I replace it with an update.

Thanks so far for the help guys.

 

I have not had much luck trying to get these carbs to work well at all. They are easily replaceable and are $23 and change at home depot with free in store pickup.

 

Howdy folks,

Got the new carb in the mail today, popped that bad boy on there.. pulled 3 times for no startup.. primed it.. pulled again and on she came! She sputtered a bit for a minute.. but I added some fresh gas (this has been sitting a week in a humid garage) and it cleaned right up.

It looks like it was the dang junk carb all along.

Thank you so much for your help everyone, I believe this is good to go!

 

Glad you got it fixed, thanks for the update!

 

Howdy again folks,

So I am back. Sadly.

The mower worked great for two mowings, Fresh gas and oil change with the Carb and everything was peachy. But a few weeks later, I started the mower up and it just isnt working right again.

Its sputtering, popping much more than it was, and shutting off every now and then. With intermittent time of working great.. Im not sure what to do next.

Any more help? lol