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Hi all,

I want to start off by thanking everyone for any input I may receive.

I have a MTD- Yardmachine. 42 in cut model 13an775s000,
with a B&S 16.5 HP power built engine model 31A707 type 0874g5 code 12110920

Now I Want to say that I was stupid enough to not drain the gas from last season and I cranked my mower up with the old gas this season. I was cutting my yard then after about 10 minutes it shut off with a puff of white smoke. after this I tried to crank it, and all it would do is spin the motor without actually cranking and running. I did some research and determined that I possibly had a clogged carburetor. before I tackled the carb, I changed the oil and spark plug with no luck. I cleaned the carb and still no luck. I ended up buying a new carb and even that did not work. I checked the spark plug and it appears to be getting a spark (do ignition coils get weak or just die?). I even went as far as checking the flywheel key and it was ok. Right now all it will do when I turn the key is turn, the engine will spin, it seems to have compression, puffs of white smoke comes out the exhaust, and it spits out a little gas where the air filter is.

Any input or suggestions will be greatly appreciated.

Thanks,

Brandon

So it wont startup is what you mean? Try starting it a few times then take the spark plug out. Is it wet?

Right it will not start. I have replaced the spark plug twice after the first replacement it smelled of gas and was a little wet, after that is when i changed the oil and plug. the plug in there now after checking has a smell of gas but is not wet.

Just to rule it out put a little fuel into the cylinder or a little starting fluid. Reinstall spark plug then try to start. Anything?
Do you have a compression tester?

I do not have a compression tester but I can probably get my hand on one and i will do the gas in cylinder option to see if it works. It will have to be tomorrow afternoon though b/c it is now dark outside. sucks I don't have a work shed outside. FYI I did attempt to use starter fluid in the air filter intake if that makes a difference. I will try that out asap and give an update regardless of the outcome. Thanks

Yeah if it doesn't try to startup or act like it wants to startup when you put the fuel in the cylinder. Then that narrows it down to spark & compression.
It's dark here too.:laughing:

Hi Mikel1,

How's it going today? Sorry I am a little late getting back to you. I did a few things, I Checked the gap on the plug (can never be too sure) and it was at .30. from what I looked up that should be correct. I did a compression test and got around 35 PSI (still looking up to see what it is suppose to be.) I sprayed starter fluid in the cylinder and nothing changed. I also got a spark plug tester the light looked weak when trying to crank it ( I could barely see it). funny thing was when I put the plug wire back on the spark plug (I kept it in the cylinder) it backfired so it seems I am getting spark but is it weak?

Compression is low. Lets cover our other bases though. How is the flywheel key? What color is the spark when testing with spark plug? What spark tester did you get, inline or the spark plug looking one with the clip?

1. Key looks good looked straight and not bent.

2. when testing the plug it looks white

3. I got an inline tester. I actually forgot that fact so I retested with it inline :ashamed:and was able to see the light on the tester.

what is the compression suppose to be? Could it be something as simple as intake/exhaust seals around the carb or something internal?

Briggs doesn't list the compression, they only tell you to use a leakdown tester. I like to see at least 60 on a 4-stroke.
I would take the ohv cover off and turn engine over slowly by hand. Observe the travel of the valves and make sure there isn't nothing broken when your in there.

o boy that sounds like fun. I was hoping that I didn't have to mess with any of that but hey got to do what I got to do. if not I am going to need more than a lawnmower to mow my lawn with all this rain we been getting. so I guess I know what I am doing tomorrow after work.

Thanks for the input and I will plan on revealing the results sometime tomorrow after I am finished. :thumbsup:

I figured we might have to go down this road when you said after 10 minutes it stopped with a puff of white smoke.

Hey, hopefully we might be on the right track. I removed the ohv cover and had a little bit of oil come out. (i assume that this is normal.) I hand turned the motor and everything seems to function properly. I brought the cylinder to TDC and trying to figure out how tight the rocker arms are suppose to be. they feel like they are both loose but how loose im not sure.

Yeah oil in there is normal. I would check to see what the current valve clearances are at while your in there. I sent you a pm with the service manual link.