Chesha Neko

I've been pretty good about keeping things greased, but I overlooked greasing the ring on the chain tensioner. I now find it is seized in place on the axle. It's only been a month or so since the last time it was removed so I was quite surprised to find it frozen, and at a weird angle at that.





Suggestions for breaking it loose?

FBinNY 

No suggestions for breaking it loose except for putting the axle in a vice, and trying to tap the tensioner around.

However, your axle is bent, and I suspect that it's related to the tensioner. I wonder if maybe you didn't use the tensioner to actually tension the chain, or even to take all the slack out. If so, the eccentricity in the sprockets, probably led to the chain being too short at the high spot and pulling the sprocket forward (the chain is the strongest part here).

Remindrr (disregard if it's not necessary) SS and fixed wheel chains must NEVER be tensioned. I cringe when people speak of tensioning these chains. Even when we all know what we mean, the term itself is misleading. The so-called chain tension you have there is misnamed. It's isn't a tensioner, but an axle position retainer, or axle anti-slip device. The correct tension for a chain is less than zero, or more precisely, enough slack so that in the tightest place, there's still clearly visible slack, that can be transferred from the lower to the upper loop by moving the crank back and forth a few degrees.

Chesha Neko

I run the chain fairly loose (at least an inch of slack), but thanks for pointing out the bent axle, that might be part of it indeed. Definitely explains why the "tensioner" is at a weird angle.

FBinNY 

1" of slack might be too much and the chain might have climbed up on a sprocket, jamming and bending the axle. Chain tension on an SS is a Goldilocks proposition. You don't want it too tight, or too loose, but just right someplace in between. The ideal is minimum slack, while ensuring that it's still slack at the tightest place.

Someplace between 1/8" to 1/4" vertical free play at the center of the slack loop, or as I do, the ability to visibly (and so you can feel it) transfer the slack from bottom to top. This is done at the tightest spot, and tested by pedaling while holding tension on the chain with a finger under the lower loop.

How much slack you'll have depends on the concentricity of your sprockets, with good track stuff having almost variation, while some lower end cranksets will have the slack loop rising and falling 1/2" or more at the center.

Airburst

Yeah, that axle won't be doing your wheel bearings a whole lot of good...

Personally, I'd be surprised if the chain tensioner had actually corroded onto the axle, I'd be more inclined to think it had just gotten jammed in the threads, possibly when the axle bent.

onespeedbiker

You also seem to have the tensioner on backwards, I believe the washer part belongs on the outside of the rear fork ends, not the inside (might explain why it's now wedged). Further, while the axle may be bent, photos can be very deceiving. Pick up the wheel by the axles and give it a spin; you'll know right away if the axle is bent. As far as loosening the mks tensioner, I would hold the axle with a cone wrench on the other side and give it a couple of whacks; I agree with Airburst, it looks more wedged than corroded.