Swingarm eating chain adjuster

[Kookas]

I've got one, it's a good tool but too expensive. Can't believe some Chinese factory isn't copying the idea and selling it for $10. It's a dot laser in a rectangle.
Doesn't really suit the sprocket on the GS500 but you can make it work.
My one needs a new battery so when I get my carburettor back from the shop, I'll go and pick one up.
I just counted the threads on the adjusters for now. I had them out and they have the same number so I'm hoping it will be good enough.

I did some hunting, and I did find a cheaper laser tool called Laser Monkey going for nearly half the price (£25 at Halfords). It seems to be a UK-only product though unfortunately, some Dragons Den thing (I don't get it because, like you say, it's just a laser in a box). I don't know if it's any good but it has good ratings. Might buy it, eventually.
https://www.tru-tension.co.uk/product/laser-monkey-motorcycle/

I can only assume the stuff is expensive because it's kind of a niche market? Bikers, but also those who want to do their own wheel alignment, but also want to do it accurately. I mean, I have a laser thermometer which cost me about £15 and it's got not only a laser in a box, but a thermometer and a screen too.

[user11235813]

...I did find a cheaper laser tool called Laser Monkey going for nearly half the price (£25 at Halfords)...

There's an old saying that goes something like "I can't afford cheap shoes", that laser monkey looks like a POS. the laster is mounted in plastic and the plastic mount is connected to a plastic gantry with large jaws that straddle the top of the sprockets. You may as well throw your 25 quid down the toilet.

The proficat is a small solid machined piece of aluminium. It's designed to work in a greasy area, thus there is no switch for the laser just the large knurled knob that you unscrew to change the batteries. It acts as a switch when it is screwed in fully the laser is off, when you back it off just a bit it allows the spring under the batteries to push the batteries up a bit where they then make contact and turn on the laser. 

It works perfectly on the GS sprocket.

I just had my wheel off today to clean some rust and I see that those metal bits that bent are 1/8" thick with pressed indentations to increase the strength. That would take *a lot* of force to bend in fact it's difficult for me to see how enough force could be applied to bend that metal without stripping the thread off the bolt or nut first!

I have clipped the first few seconds of their promo video and you can see the whole thing wobbling from side to side which sort of defeats the whole purpose of it.