2004 Murray 13.5HP Stalling & Backfiring

[rrobertson]

Hi Everyone,

I inherited a 16y.o. Murray 405000X31B when I bought my house a few years ago. I changed the oil and spark plug when I got it as it wasn't well taken care of. It ran well for a few years before I hit trouble.

Last year I noticed that every time I went to mow the fuel tank was empty. Thinking it was a slow leak I replaced the fuel line, filter, and added a shut off valve. This seemed to fix the leak.
Carry on a few more months and the tractor will sputter, backfire, and stall. I had a newborn at the time (read: no time to work on it) so it sat in the garage all winter. This spring I pulled the carb, sprayed it down, and put some fresh fuel in the tank. The mower started up and ran OK, however as soon as I shut it down fuel spilled out of the carb overflow. I traced that back to a damaged O-ring on the fill side and have since fixed it.

Problem solved right? Wrong

Now the mower will start and drive (and occasionally let me engage the blades) but tends to stall out under load, and backfire like crazy. I can usually start it again on a low throttle setting but it still stalls out shortly afterwards. I have a feeling it's due to carb setup but it doesn't really respond to any changes I make. It's got the B&S 13.5 I/C series engine (2BSXS.3442VM 275112)

Does anyone have suggestions on how to fix? An idiot's guide to setting up a carburetor? Overlooked items?

Thanks for all the help!

 

[keakar]

not sure what you mean by "damaged O-ring on the fill side " but your issues are the float needle was leaking gas into the engine flooding it

a shut off valve doesnt fix the issue it just stops the leaking issue so replace the carb with a new one on ebay for like $12 and that will stop your fuel issues

as for the rest, i hope you replaced the oil since thats where all that missing gas went and if you didnt it can ruin an engine quickly if you have gas mixed in your oil.

the popping and backfiring could be a flywheel key issue or even a worn cam from running it with gas mixed in the oil or even just all that gas mixed with the oil inside the engine

start with your main problem first, replace the carb with a new one, then if its still having issues move on to checking the flywheel key position

 

[Scrubcadet10]

keakar has you pretty well covered, I just want to stress check your oil, if it smells of gas or is over the full mark, drain it and replace, New filter too if it has one. Gasoline diluted oil is a quick way for the engine to go to the great big boneyard in the sky.

 

[bertsmobile1]

Idiots guide to cleaning carbs

 

[rrobertson]

Wow! Thanks everyone for the help!

The oil level has always been good, however I drained, flushed, and refilled last night out of precaution. It was dark, but didn't smell like gas. I also pulled the flywheel - no damage and the key wasn't marked up or split. I pulled the spark plug (I know, should have checked earlier) and it's black with soot. Going to replace later today, but it confirms my suspicion of rich mixture.

The carb guide is fantastic - found mine (Nikki for B&S) and will use it tonight to double check all the jets and re-clean. Going to have the FIL come over this weekend and we'll try to get it adjusted in.

As for those 'cheap' replacement carbs - any leads on places to get them or is Amazon the best option?

 

[bertsmobile1]

A small mower shop that does repairs & sells used / reconditioned mowers.
I get my carbs from RGS or Stens or CTS because all of these come with a warranty.
If you are using evil pay click on the "other Items from this seller" link
If you get 50 pages with everny from condoms to air conditioners go some where else.That vendor is a surplus goods vendoe and has no idea what they are selling & no idea if they were overproduction or rejects to be scrapped.
If the vendor has all carbs or all lawn care items then there is a better chance that they actually know what they are selling.