# Bad Day for the ST120



## Brother-Al (Jul 22, 2011)

Well, My Beloved Bolens ST120 Hydro is telling me she's not too happy with me. Perhaps its the mostly complete ST110 11hp/manual sitting next to her, or the fact that she was worked too early back in March... either way, its been one thing after another with her for the past month. After sitting dormant from November thru to Mid-March, I pulled her out, put in the battery and she fired up after two cycles... 
Worked her easy and let her run at low idle for about 15 minutes then gradually worked her up through the RPMs over another 15 minute span, then changed her oil. Oil looked pretty good actually, running B&S full synthetic through her and couldn't be happier with the results I've seen. I hitched up the lawn cart and took her around the yard a few times, picking up debris from last winter, leaving her running the whole time. Maybe was another 15 minutes or so... I took her out to the front yard and began to clean up a pile of thatch I had raked up earlier in the day. As I was finishing, I heard her start to miss and sputter, then she coughed hard, died, and backfired loudly... WTH?!? I went over and tried to restart her.. she fired up and then immediately died again as soon as I brought the RPMs down and adjusted the choke. (she prefers a medium throttle and choke adjustment combo to run happy at start-up). I checked the gas and still had an almost full tank (gas cap guage has become impossible to read). I checked the fuel filter and it was full of crud! Hmm, odd, shouldn't be anything in there  Ahh well, who knows.... Cleaned the line out, new fuel filter, she fired right up... ran her a good 10 minutes, but she had a slight stumble now but was running ok, but nowhere near as nicely as I'm used to. took her out back to dump the thatch and turned on the electric PTO to test out the mower deck... she stumbed even worse, barely had a chance to get her to my compost pile, where she fell flat on her face and refused to restart... had to drag her back to the house... manually :dazed:
Fast forward to today, finally good weather and free time coincided in my schedule, so I got to work on the 'ole girl...put a fresh charge on the battery, rechecked the fuel line... tried to start her... nada, shot of ether, "Varoom", came right to life then promptly crapped out... Hmm, ok rechecked that the fuel pump is working, yup... hmmmmm, I dunno. so I go to try again and the damn ignition switch breaks, the key actually turned all the way around 180 degrees without doing anything...
So I go over to the carcass I bought as a possible winter plow/snowblowing tractor, pull the ignition and swap them, turn the key and I'm rewarded with a "POP", 30 amp ignition fuse blew.... Grrrr! OK, time to call it quits for the night.
And so here I am, wondering why she wont run with good air, fuel, and ign/spark... and that I will need to get a new ignition...
If anyone has any thoughts/ideas about my issue, please let me know.
for the record, she's a 1988? Bolens ST120, Briggs and Stratton 12 HP, 4 cycle, I/C, with the Hydro trans... 
(No, Thankfully, MTD did not own them back then, Troybilt did tho).


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## jhngardner367 (Apr 5, 2011)

Our "Ladies",can be temperamental! Any chance some of the crud got into the jets?A shorted coil,or a bad wire?


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## Brother-Al (Jul 22, 2011)

much delayed update...

She's running better than ever now that I sorted her out...

I was suspicious that E10 Deathanol was to blame. Unfortunately, all we have up here in Mass is E10... My suspicions were proven to be correct. I opened up the fuel bowl and found that notorious clear, jelly-like substance on the float, pickup, and in part of the bowl... also found in the bowl was a thin layer of rust that was not there last Spring... 

Rewind, Last fall, in anticipation of the 2011 late-October Snowstorm, I had treated the gas tank with Startron and also added some fresh gas treated with Sta-bil's new Ethanol Treatment, but had I had not run the engine after treating it... I had intended to, but that snowstorm's level of destruction here in Southern New England was crippling. I had no power for almost 2 weeks myself and the last thing I thought about was my Bolens... until March anyway... never remembered that I had not run her, so the bowl sat full of E10 deathanol.

So anyway, I pulled the carb off and realized that my rubber fuel lines were disintegrating from the inside out and that is what was in my fuel filter... Deathanol strikes again... I replaced all of the fuel lines with deathanol-suitable lines and cleaned out all of the crud from the carb... then I polished the inside of my fuel bowl to remove the rust, before it became worse.

All said and done, she runs beautifully. My ignition is still fubar. The "replacement" units have a different polarity and that is why they were blowing fuses... damn good thing Bolens/Troybuilt still engineered quality machines back then, (pre MTD buyout).


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## jrtepperary (Mar 7, 2016)

I have a st120 also. I am looking for a ing switch or part #, its not a round switch, the wire plug is like a "w2" any help?


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