I hardly call these issues really... The 125 is known for the shift stopper breaking, its so common i had two of them on hand for replacement! They are a ten dollar part brand new. They pop out of gear and won't always go beyond 1st or 2nd when they go, but if caught fast enough you just remove the broken piece and replace it and life goes on.
As for the filter and brakes, wear items that go bad, not much you can do to prevent it. After getting some riding time in it just jiggled crud around in the tank and the filter took it in the shorts, flipped the tank to reserve so the strainer on the carb was only thing inline and managed to go a little farther til that plugged up with sediment from the bottom of the tank as well. Pulled it apart, cleaned, and started back up first pull. Not a big deal for me.
The brakes were most likely due to not being used much, if at all. The shoes were almost full thickness but everything got stuck and wouldn't retract and the bottom shoe fractured from the stress and broke, jamming the brake up. I replaced the brake cable for the hand control, the cable was seized, after about an hour of riding she grabbed the brake hard and the rear was locked up, took all the linkage apart and the brake wouldn't move. Tore into it, removed the brake shoes and greased the linkage, everything moves fine so once i get new shoes this week i will put it back together correctly, for now its back together and running fine without the shoes in there.
Like i said, got to expect this type of stuff. The motor is strong though, compression tests good. She smoked a bit after an oil change, pulled the plug and inspected the cylinder and it looked good except for a bit of surface rust. After a couple hours she stopped smoking and isn't losing any oil. Just needed a good workout after sitting for a while, might need rings and a valve job eventually but for now its not worrying me any.
I don't buy a 27 year old machine and expect everything to perfect.... LOL!!
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1984 Honda ATC200ES "Big Red"
1982 ATC200E "Hondie"
1988 TRX300FW "Project Quad" Still in progress....