mtd yardman, self propelled 22" mower
model #12A-26MBO55
serial#1E17K3124

it won't start..it wants to, but it just won't catch..it makes that "chugging " sound...it turns with the pull rope just fine, but just doesn't seem to catch...

i bought a spark tester and it has excellent spark
i bought a new plug, gap is correct .030
i took the carb off twice..it is really clean, float is working
it is getting gas to the carb..bowl on bottom had gas in it both times

my book said to put a teaspoon of gas in the where the plug goes, put the plug back in (put boot back on), and try to start it, if it starts for a second, then it is a carb problem..i did that and it didn't change a thing..still wants to start, but it doesn't

i checked my cables..they are opening the choke properly and the taking the brake off of the blade properly

i took the flywheel off(desperate)..book said it could be a partially broken woodruff key...woodruff key is fine..put the thing back together, set ignition coil gap at .010 (book), and still nothing...
my book is out of answers and if i could lift that thing i'd throw it..it is only 2 years old, and i don't think i've used it more than 7 or 8 times...
i am out of things to check...there just isn't anything else left to that mower, is there??????????????????
I looked for points when i took the flywheel off..i have an old repair book..i couldn't find any?? do the new mowers not have points??? My manual that came with the mower has an engine breakdown and it doesn't show points anywhere??
oh...and it's not old gas..i was actually mowing with it when it quit..seemed to lose power, dog out, then died..i bought new gas just to be sure...
any ideas you can give me on where to look next?? this can't be this hard, i have to be missing something obvious??? thanks.. It is ***of course*** out of warranty

I can't seem to find you mower at the MTD site, if you would post the engine numbers usually found on the engine shroud just above the spark plug it would help, however after reading your post it sounds like a bowl nut(main jet) problem. Tecumseh and some B&S have metering holes in the bowl nut, the one that usually creates the most problems is the tiny one at the top on Tec engines the link below will give you an example, there can be from 0 to 4 holes so look carefully, I use the wire from a twist tie to clean the tiny one. Have a good one. Geo
http://i190.photobucket.com/albums/z120/geogrubb/tec_bowl_nut.jpg

sounds like your flywheel key is bad, or you have a valve not working properly

just because a flywheel key doesn't look bad, doesn't mean a thing, I've replaced them where they looked great, mower wouldn't start, replaced it, it sat there running, it does not take much at ALL to get these out've time

now, if you have a tecumseh motor, I would be guessing camshaft, because I've been replaceing alot of camshafts on newer tecumseh motors because the plastic ring gear does not hold up at all

these are the numbers off of the engine...
lot # 060900330421
1P65FUA0610081A0276
this is the parts diagram my book has..
http://www.partstree.com/parts/?lc=mtd&mn=12A-26MB055+(2007)&dn=6902298B0002

i will go out today and get a new key and clean the carb again..hope something works. Thanks

oh my, you have one of THOSE motors

take the valve cover off and roll the motor over and watch the valves work, make sure they are moving the same amount

Also for good measure replace the flywheel key anways they are only $1 or so, Also make sure the center jet on the carb is clean. There is small holes up and down it run a the wire of a bread tie through the holes then clean with carb cleaner ( the cheap stuff in the blue and black can at walmart works just fine). Also do what pyro said check your valves under the valve cover, make sure there isn't to much space between the rocker arms and valves.

mtd yardman, self propelled 22" mower
model #12A-26MBO55
serial#1E17K3124

it won't start..it wants to, but it just won't catch..it makes that "chugging " sound...it turns with the pull rope just fine, but just doesn't seem to catch...

i bought a spark tester and it has excellent spark
i bought a new plug, gap is correct .030
i took the carb off twice..it is really clean, float is working
it is getting gas to the carb..bowl on bottom had gas in it both times

my book said to put a teaspoon of gas in the where the plug goes, put the plug back in (put boot back on), and try to start it, if it starts for a second, then it is a carb problem..i did that and it didn't change a thing..still wants to start, but it doesn't

i checked my cables..they are opening the choke properly and the taking the brake off of the blade properly

i took the flywheel off(desperate)..book said it could be a partially broken woodruff key...woodruff key is fine..put the thing back together, set ignition coil gap at .010 (book), and still nothing...
my book is out of answers and if i could lift that thing i'd throw it..it is only 2 years old, and i don't think i've used it more than 7 or 8 times...
i am out of things to check...there just isn't anything else left to that mower, is there??????????????????
I looked for points when i took the flywheel off..i have an old repair book..i couldn't find any?? do the new mowers not have points??? My manual that came with the mower has an engine breakdown and it doesn't show points anywhere??
oh...and it's not old gas..i was actually mowing with it when it quit..seemed to lose power, dog out, then died..i bought new gas just to be sure...
any ideas you can give me on where to look next?? this can't be this hard, i have to be missing something obvious??? thanks.. It is ***of course*** out of warranty

remove the cylinder head and see if the cylinder is scored IE chopped up and rough if it is it wonk run too much blow by, if it is its most likely in need of replacement