On the positive side, I fixed the two top gears on the recumbent

On the negative side, I've had this exact problem before and forgot about the cure.

Turns out that waxing the chain makes the cassette "fill up" easier so the chain cannot sit properly in the cog's teeth. The 11 and 12 tooth suffer most because they're so low - the caked-up wax fills the valley and compacts, holding the chain off the teeth,

I guess having triple the length of chain that a regular bike has also brings more wax to the party.

Someone likes small wheels.

Odd maintenance task. The FD shifter was completely stuck while trying to lift the chain to the larger chainring. It felt as if I was going to break the shifter. (Then, oddly, when I did push too hard, it snapped in without actually pulling the cable. It seems it has a failsafe mechanism after all.) In any case, it turns out that the cable (bottom of the picture) was stuck in this groove (bottom of the bike).

There was no mud or sand. Just somehow stuck. Simple enough: I sprayed WD-40. Waited a minute, then hosed it with water at maximum speed. Dried. The added some dry lube.

Questions: 1- Dogma says never use a water jet, but if you aim at a specific location, it's alright, no?

2- Is it my imagination, or do road shifters actually have a mechanism that yields without pulling the cable, rather than destroy the internals?

This seems minor, but I could ask as a formal question if you think it's worth it.

(and why am I certain that the cable was stuck at this location? Because I could pull the cable by hand ahead of it, but not behind it.)

(ahead = closer to the front derailleur)

@MaplePanda Thanks for all the details. IIUC Powerspline BB is a category, not a particular product. Are you saying then that they don't last because of poor design in some place, such as the crank to spindle connection? Or are the bearings the weak points? If the latter, there must be someone who does it well, no?

@Sam It's kinda just an implementation issue. There are a few models of mid-tier hardtails (eg Trek roscoe 7) from various brands which all seem to use the same crappy BB from the factory.

Like, die in 500km crappy

@MaplePanda I want to see this data on Strava immediately!

You can buy me the power meter :)

@MaplePanda Unclear... The Trek Roscoe 7 has "Shimano SM-BB52, 73mm, threaded external bearing". That's not a powerspline BB; is it?

@Erlkoenig does "Kett Err Alu Rad" mean anything special or just the original name on the frame ?

I bet the handling is super-twitchy

I note this bike has a trailer hitch with a trailer connector dangling in it - like the trailer's draw-bar fell off at some point

@Sam Only the 2019 and 2020 models I think.

There must have been a lot of warranties

Also do note the 2023 roscoe is an entirely different bike now

You did the right thing by freeing the cable, and lubricating it. That should work fine for a couple years more.

@MaplePanda 2023s are out already? I thought we had to wait until October.

@Criggie The modified rule that I intend to follow is this: As long as I am certain I am not aiming the jet (from a nozzle at full throttle, not actually from a power washer) at any bearings (headset, BB, hubs) or any stanchion (dropper, suspension), that that's perfectly good.

I just tried it on stubborn rim brakes, and for the shifter cable. No bad side effects so far.

@Criggie Both front and rear shifters were shifted, a bit excessively even, to keep the cadence within a very narrow interval. Then I thought I'd loan the bike to a friend as an introduction to road cycling. Though the test ride was only 3km, and I was following on another bike, the cable was stuck afterwards. Lesson learned: test rides are to be done at cycling stores.