Problem with a new mower.

[Salty]

Hello all, and thanks in advance for the advice.
Last fall we moved into this ranch home from a duplex. Needless to say I didn't have a mower so I was given an old used one that lasted for about 4 mowings. We then decided to buy a new Craftsman rear bagger, 21" with large rear wheels but NOT self propelled. That thing worked great for the rest of the cutting season. Because there was so much to do to get the house winterized I neglected to properly store the mower and left it with some old gas in it. Well, this spring it began to act up by surging and using way too much gas. The yard isn't very big and last fall I could mow the whole yard twice with 1 tank of gas. Now it takes more than a full tank for just 1 mowing. When it first starts it runs fine for about 30 seconds and then starts to surge and puffs small amounts of black smoke. It starts up fine, just as it did when new. Just 3 or 4 pumps of the primer and away it goes. It also restarts fine when hot. I have ran through about 3 tanks full of fresh gas, gas that was also put in my car and used in the trimmer and both those run fine. I also noticed that it runs really good for about 30 seconds just when it is running out of gas.
So, I am wondering if something got gummed up and is causing it to run rich.
There are no carb adjustments on these things so that isn't an option and there is no speed control as it is adjusted by the govenor.

Any suggeations as to what my options may be?

I did clean the air filter and that didn't help. I also ran it for a minute without the filter and it still surged. I pulled the spark plug and it was covered with black carbon. Cleaned it and finished mowing and when checked again it was again covered with carbon. I doubt that it needs a new spark plug this soon, especially since it starts up fine.

Dale

[Pappy]

Sounds like you need to clean the carb. They are pretty simple so it's not a hard job. Just make sure you have a good work space to keep track of small parts when you disassembly it. I generally cover my work surface with an old towel and work on that.

[Salty]

Thanks Pappy.
Should I go get a repair kit of some kind so that I have replacement gaskets and such?

[gerti]

This thing wouldn't have a choke stuck on open?

[Jim Boyd]

Thanks Pappy.
Should I go get a repair kit of some kind so that I have replacement gaskets and such?

On a newer mower just be careful and the gaskets should remain intact. Count the turns on your mixture screws so you can get them back close on re-assembly.

[JSUPreston]

Outdoordistributors.com will most likely have all the parts you might need, hopefully a little cheaper than Sears.

Hope it's not a Tecumseh engine. I've got a push mower that died that has one, and one of the high wheel weedeaters that has one. I'm tired of constantly fixing them. Give me a Briggs instead.

[rg32]

I'm a 2 cycle Lawn Boy person myself.
Does it have a Briggs?
Just from experience
Besides from a dirty fuel system and giving it a good cleaning
A sticking governor can make the automatic rev limiter jump back and forth and make the motor surge and even use more gas.
Check for sticks and leaves around the carburetor and governor links. If clear of debris hit it with some carb cleaner and then spray with wd40.

[Salty]

Thanks all.
It is a briggs, 4.5HP I believe. No adjustments or mixture screws at all unless they are inside the carb. It looks to be the same kind of 'no-thrills' version that I had on the used mower. Since it was/is rather new I hadn't looked at it to closely until it began acting up. The govenor spring seems to work fine and without obstruction. I was able to manually rev it up by moving the flapper, which must also be the choke on these things.
I noticed that the manual says not to use carb cleaner products on this. Possibly due to the extensive use of plastics. That stuff can be very agressive on plastics.
I guess I'll take it apart today and see what's up. I had the 2-cyle trimmer motor apart last year and reassembled it with the old gaskets. That thing starts every time now and usually without choking it first. Maybe I'll get that lucky on the mower.

EDIT.....
Just finished taking it apart and cleaning it. Fresh gas and an oil change. Didn't see any real problems but there was a small amount of dirt in the sediment area of the tank.
Runs much better. Still has a slight surge but it definately runs better. I'll see how much gas it uses next time I mow the whole lawn.
Thanks for all your help.

[Lee4847]

Test mow

If you want to test it... My grass needs mowed!!

[rg32]

Similar diagnosis
Salty soon after I read your post I went out and fired up my “back- up” mower which has a Briggs and started mowing. Almost immediately it started to serge and blow black exhaust.
I cleaned the governor and breather tube and drained the fuel and flushed the tank, reinstalled (It still acted the same).
This is when I completely disassembled the carb and soaked it.
Some observations and it is running well again.
The (diaphragm) between the tank and carb body was slightly sucked through in one area and possibly allowing air to be pulled in.
The “O”ring that seals the carb to the block was not seated well and possibly allowing air to enter.
Was it the thorough cleaning or the repairs I made, not sure?

[Salty]

Good observations rg32. How many parts did you replace besides the diaphram and the o-ring? Is the diaphram part of a second gasket between the tank and carb?
In my case the o-ring and gaskets looked good. My suspition is that there was, and still is, some deposits that gathered because I left it sit over the winter and did not winterize it.
If it does not mow the whole yard next time on less than a tank of gas I will rebuild it again with some new parts. I never went to rocket science school but these things don't seem to be that complicated and I just don't want to spend $50+ on a sevice job on a new mower.



And no Lee, I am not lugging that thing all the way down there to mow your lawn....but thanks for the offer!! :-)

[rg32]

Hi Salty.
Yup might just need a good cleaning.....
They are straight forward: just clean everything well, keep track of the parts and take your time.
Not that old either, my mower is < 2 years old and given to me by a neighbor and it looks show room.
The diaphram (I call it that?) is the bottom gasket of 2 between the tank and carb body, (flexible, paper-thin and fragile).
I did go searching (local hardwares) for the diaphram but had no luck so I carefully cleaned it and then sandwiched it between two pieces of ceramic tile weighted down to flatten it out and get its shape back. I used Vaseline to hold it in place then tightened the carb down.
I did replace the “O” which is a standard cheap hardware store item,
no other parts replaced.

The last Briggs powered mower I worked on had a cast metal carb body, good point about the carb cleaner as it is all plastic.
Good luck and hope this helps

[jhart]

There is a product called Sea Foam that you pour in with your gas and it does an amazing job of cleaning out old deposits without having to take the thing apart. Not sure if it is distributed nationally, but a search on the internet should come up with some places to buy it from if not available locally.

[frumper64]

Seafoam

Locally, the NAPA parts store carries Seafoam - I never tried it on a mower, but put some in my truck when I think about it. Seems to do a pretty good job

[Salty]

Thanks for all the responses folks. Apparently whatever I did worked. I just mowed again today and it is running like new. Filled the tank, mowed the whole yard and there is still plenty of gas left in the tank. Amazing!