3d ago

Advice requested: Repairing a mountain bike, can't calibrate rear derailleur

We are pretty stumped. My 11 year old outgrew his last bike, and rather than just buying a new one, we went to a local bike operation called the "Sacramento Bike Kitchen" that restores bikes and teaches bike repair. They sell refurbished bikes, but if you are getting a kid bike, it is free, and if you buy an adult bike for a kid, they give you $100 off. We decided to turn this into a learning opportunity and got a mountain bike for $70 (so free) that had a decent frame, but a lot of parts were in pretty rough shape.

We brought it home and went on Amazon and got new treads and inner tubes for the tires. The gear shifters were pretty broken (it is a 3x8). So we went to Amazon and got new gear shifters, handlebar grip shifters, but when we replaced them we could only get the rear derailleur to go the distance of six out of the eight gears, even with adjusting the barrel adjuster ane confirming that the low and high set screws were correct. No matter how far we used the gear shifter, it would stop at 6 gears; it's like the barrel adjuster would move the range up and down, so the shifter would go from gear 3 to 8, or 1 to 6, but would never reach 1 to 8.

I then started watching more YouTube videos, including everything by park tool, and found some advice that it's possible the derailleur is incompatible with the gear shifter. We then decided to replace the rear derailleur, but the new one had the same problem. We then got some advice that it's possible the rear cassette was incompatible, so we went and found a rear cassette that is listed to be compatible on Amazon and replaced that as well. From all the adjusting, we also mangled the cable and thought that a thumb shifter would be better, so we replaced the gear shifters again. As long as we were replacing everything we decided to replace all the cable housings as well.

At this point we have now replaced the rear derailleur, the rear cassette, the chain, all the cable housings, the gear shifters with thumb shifters, and then we have also replaced the seat, the handlebar grips, the kick stand, and the treads and inner tubes. At this point, the bike is in perfect condition except for the stupid rear derailleur. We are totally stumped and before we go back to the bike kitchen (which has limited hours and is kind of far from where we live) I am looking for some advice. Everything I read is pointing to the fact that it should be the barrel adjuster to get me where I need to be, but every time I do it, it shifts the gear shifting range up and down, but doesn't stretch it. This is with two different gear shifters we have tried.