# Bolens ST 125 Hydro - Need belt



## GreenFlyer

Hello,

I am working on a Bolens ST 125 Hydro. The engine to transmission belt broke off. I can not find a service manual, or any link on the internet, that has the information for the exact size belt required. The belt is shredded and part of it is missing, so I can not tell what the required size is. Anyone on here with some info about the correct size belt would be of great help. Thanks.


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## js5020

Here's a couple of links for parts and service manuals for Bolens machines,,, Sonny's Farm & Home Supply Sam's Bolens hope it helps.


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## GreenFlyer

*RE: Belt search*

Thank you! I found the part number and belt I need. Thanks again! :usa:


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## GreenFlyer

I finally found a drive belt to fit the Bolens ST125 Hydro. It is an 84", 'A', drive belt. The Bolens' diagram lists it as an 84.5". This one fits perfectly. Now I have to get a new battery to start the darn thing. And why did Bolens have to put the grease fittings on the spindles BELOW the deck? Good grief. What were they thinking in the mid 1980's? It is a nice, simple little mower/tractor.


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## js5020

LOL ya I'm not sure why they put the fittings on the underside of the 36" decks, now the 42" and 48" decks have them on the top. The ST series to me, is a great machine as long as its kept within reason,, its no tubeframe for certain but it is an excellent mower and lawn chore machine. Is your 125 a twin cylinder or a single? I have a 160 gear driver and have an 18 in it now and recently accuired an 18.5 twin ll for it, yes pretty simple most parts seem rather generic or easily fabbed except the steering gears, which seem to be the weak area.


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## GreenFlyer

It is a 12.5 twin. It is a very simple machine. I have to get a new battery and it should be back up and running. I was told the kids left the key 'on' in the ignition for several days, and could have been as long as two weeks. My trusty multi-meter read 12.5 volts on the battery. I tried charging the battery with a trickle charger, but no joy, (the mm then read 12.8 volts. I tried 'jumping' it, battery-to-battery', with my pickup truck,(truck running at 2,000rpm). I let it charge for about 5 minutes before attempting to turn it over. It turned over twice, then would not budge. I think the battery has dead cells in it. I will post the results when I have them. Later...


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## js5020

An issue I had with mine once was a bad ground connection, another was the bearing in the pto clutch was "dragging" and was tryin to turn the deck a bit while starting, and just about every opposed twin I have ever gotten has had a bad starter on it, you might want to check the amp draw on that.


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## GreenFlyer

Thanks for the info. I did notice the starter smoking a bit while attempting to start it last week. I also noticed during a start attempt that the voltage on the battery dropped to between 8 and 9 volts. Is the starter an easy fix or something very involved? I can fix just about anything with a tech man in front of me. The pto clutch is not 'dragging'. Thanks again.


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## js5020

Nah, its not a big job as the starter itself is only on by two bolts, however depending on the particular unit there maybe a few other items that might need to be removed to get to it. My ground cable is attached right under the starter on a motor mounting bolt and got corroded a bit and caused problems.


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## GreenFlyer

Thanks. I will be working on the tractor tomorrow.


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## GreenFlyer

Well after a few busy weeks of doing other things, I finally got time to work on the 'ol Bolens Hydro. The starter was not as hard to remove as I thought it would be. I removed some sheet metal, and two bolts, and it came right off. It is mounted vertically. I cleaned all wires, including the ground, and had no problem getting 11.5 to 12 volts to the starter. But it would not turn. With the ignition key turned to 'start', I used my trusty multi-meter and it showed about 12 volts getting to the starter, w/everything grounded as required. I took the starter apart. Everything was clean on the inside. The (4) brushes were clean and in good shape also. I gave everything a good cleaning with a toothbrush and put it all back together. If anyone tries to do what I just did, you can use (wood) toothpicks to hold the brushes/springs while you are attempting to put it back together. Use the fat end of the toothpicks. Two of them on one side of a brush, through the back of the plate, will hold each brush recessed so that you can go on to the next one, and do the same. They will stay in place long enough for you to put the plate on over the shaft. I am sure there is a tool out there to make the job easier, but at the present time I do not own one. So I just used two toothpicks per brush to hold them back while I re-assembled the one end. I re-assembled everything on the starter and grounded it against the cylinder cooling fins, and turned the key. Just clicking at the solenoid. I tried a few more times and the starter shaft made an attempt to spin once, but it would not continue. So I took it to a local, trusted parts supplier. One of the guys took it into his shop and confirmed that the starter was bad. I ordered a brand new one for $103. Not too bad for a new starter I suppose. Again, it is a vertical mount and it has some weird indentations on the mounting block. I am thinking that because the starter is installed right up against the left cylinder,(twin, 12.5hp Briggs & Stratton), about 1/8" away, that the heat generated from the cylinder is probably not good for the magnets in it. There are no shields between the starter and the cylinder. Any thoughts?


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## GreenFlyer

Finally got the starter installed today. After I buttoned up the sheet metal surrounding the engine, I had to fix the front left tire. It was flat. It has had a leak all summer. I decided to try some yellow, fix-a-flat, 'goo' that my Dad had in his shop since the Spring of this year. After removing the tire, I noticed that the wheel/shaft had not been greased for a long time. The grease that was there, was a dark, hard, 'paste'. So I cleaned it off and spread some John Deere 'green goo', grease on it. After filling the tire with the yellow 'goo' that was left in the bottle,(half full), I figured that would do the trick. I pumped it up and installed it. Knowing what this wheel's shaft looked like, I thought I would err on the safe side and pull the other front wheel to check the grease situation. Good think I did. It was so dry the shaft had grooves wearing into it. I cleaned it off and greased it. After installing the wheel, I made a thorough check of everything I worked on. And then came the moment when I would see and hear if this new starter would work. I set the brake, choke, and throttle...turned the key and the engine turned over like a champ. The only problem was it would not start. It puffed a few clouds of smoke and hinted that it wanted to start. But no joy. I pulled the plugs just to see if anything was wrong with them. The left plug was a bit wet. I looked into the cylinder and could see some gray smoke swirling around. I checked the gap on the plug... .026. I was not sure if this is the correct gap, but I figured it had to be close. I pulled the right plug and it was bone dry. It had a little bit of gray smoke swirling around in the cylinder. I replaced both plugs after cleaning them with a wire brush and decided to give the engine another try. It started after several turns of the engine. The transmission drive belt's 'idler pulley', with the spring tensioner, in front of the transmission, was making a 'tapping' noise against the underside of the frame. I let it continue to run. As long as it was not tearing itself up or causing any real damage to itself or the underside of the frame, I let it go. I drove it around the driveway for a few minutes, checking out the controls. Then I went for the big test...engaging the PTO. I have never been a fan of electric PTO's. And I never will. This Bolens HST has a rocker switch to engage the electric PTO. I will say it again. I do not like them. I prefer having a lever attached to an idler pulley that provides tension to a belt that drives an attachment, (unless it is driven by a hydraulic motor). I think they are much simpler to use and easier to work on when it comes time to do maintenance or repair. Last year I was mowing a lawn for a relative who had a Cub Cadet ZTR. The damn electric PTO flew off the shaft. Literally. When I attempted to put it back together, the 'key' was still stuck in the groove, with about 1" of it bent into a 30 degree 'Y' shape at the end of the engine's shaft. I had no way to get a key at the time. So I grabbed a hammer and went over to the woodpile. I found the chopping block and began tapping on the key to try to bend it back into a straight line. Well, I did. It was not 'exact', but it was straight enough to get onto the shaft, and allow the electric PTO onto the shaft when I tightened it. So I ran the Bolens' mower deck for a few minutes. Ran it around the yard a bit and it ran just fine. The tapping noise the tension pulley made was gone. I let the engine run a few more minutes and then shut it down. I liked working on this tractor. Everything was pretty simple and straightforward.


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## mnj777

Anyone interested in a 42" rear discharge mower for a Bolens ST125? It is in very good condition. I am in Northern Ohio.


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## dangeroustoys56

GreenFlyer: I dont like fix a flat- proof that its bad stuff was on a set of chrome rims off my dads 79 f150 that i ran on my 89 f150 after he sold the truck . The tires were around 10 years old and tread thin, so i bot a new set of tires - the one pop had a leak in was actually the worst - the fix a flat made the entire rim rust badly- all the rest were still like new ( those rims were about 10 years old too). I use tire slime, it lasts alot longer and seals alot better .


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## GreenFlyer

I agree with you about fix-a-flat. I do not like the stuff either. But it was all I had at the moment. I have been using Slime for the past 5 or 6 years. That green stuff is great! My Uncle introduced it to me about 6 years ago when I was working on a JD 4400 combine. I put a bottle of Slime in one of the rear tires and it has held to this day. I picked up a Slime 'plug kit' at WalMart two weeks ago to fix a flat on my Mother's car. It is still holding. I used a slime plug on a flat over a year ago on the same car, different tire, and it held until about two months ago when it picked up another nail. I just went and got another tire. I did not want two plugs in the same tire. Normally I would not let a plug go that long on a car tire, but I used it as kind of a 'test' to see how many miles it would last. I used to work at an Exxon gas/service station and I plugged tires all the time with a mushroom-type plug. I do not remember the brand name of those plugs, or the gun-like device I used to insert them. After inserting the plug in the 'gun', I placed a small, plastic tip on the nose of the barrel and then pushed it through the hole of the tire until the stop, then pulled back and the mushroom end of the plug would seat itself on the inside of the tire. The plastic tip remains in the tire. Excess was simply cut off. Today I will stick with the Slime. If anyone knows of a better tire plug solution than Slime, please let me know.


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