96 GT Karakoram Chain suck marks - is there a reasonable fix?

[ThePrivateer]

Dear community

I am in the process of rebuilding a 96 GT Karakoram.
The frame has quite some patina- which I am ok with. But the situation behind the crank is a bit messy


what I did so far
- remove the obvious rust with sandpaper
- use phosphoric acid on it

what I consider to do:
- repaint a 10 cm part of the chain stay (grey primer or black). The yellow hue is hard to get right, as proven by my experiment close to the mavic decal on the left.
- repaint the whole chain stay ?
- only use clear coat on the bare metal parts?

any suggestions ?
thanks in advance

 

[vtwinvince]

I usually do the bare minimum, touch up as best I can and leave it. The rings usually hide a lot of that anyway.

 

[ishaw]

The area that's marked seems to have a nice, natural section that's flat. I'd sand it a bit, build up some primer to help creat a flat surface (unless you want to flat it first), then I'd mask an area just larger than the flat bit. Spray in as close a colour as you can find, fine sand the over spray on the stay so it's flat and blended in. You may not notice the difference in colour much at all. I'd perhaps clear cost the whole stay. Fit chainset, stand back and see if you can notice much.

 

[minor_LEGEND]

Getting some primer under your chosen colour is vital. Anything dark under the yellow will make the match worse. I would get some zinc primer on it, flat that down with wet n dry, use a yellow or white primer next, flatted down before the yellow.

 

[ThePrivateer]

BTW the crank that caused this is an fc m569. Which is an oddball construction anyway …. As the teeth are worn out as well and there seem to be no spare parts, this will have to go - am thinking of going 1x9 for this bike.

 

[minor_LEGEND]

Not one of Shimano's finest creations.

 

[Oldtat]

I like the look of that crank. Escheresque.

 

[enigma]

Thats an ideal shape with an edge to brush paint... model paints are decent enamel paints and will last better than any spray for touch ups like that in my experience, I would use some rust converter as it also gives a good etch to overpaint.
Enamel cannot be spray laquered but you dont need too, and avoids having a scratched but shiny weird chainstay...
I have done similar and used an old school wrap round neoprene chainstay protector to help disguise the paint, and obviously reduce chain clatter and future damage along the rest of the stay.

As for the chainset, I don't like four bolt chainset's, but those things I never liked either, that was the groupset with the shiny shifters I actually do like! From memory not particularly light so a weird design really.

 

[ThePrivateer]

I like the look of that crank. Escheresque.

The look is fine. But it doesn’t seem to keep the chain on. And try to find a spare chaining

 

[ThePrivateer]

Thats an ideal shape with an edge to brush paint... model paints are decent enamel paints and will last better than any spray for touch ups like that in my experience, I would use some rust converter as it also gives a good etch to overpaint.
Enamel cannot be spray laquered but you dont need too, and avoids having a scratched but shiny weird chainstay...
I have done similar and used an old school wrap round neoprene chainstay protector to help disguise the paint, and obviously reduce chain clatter and future damage along the rest of the stay.

As for the chainset, I don't like four bolt chainset's, but those things I never liked either, that was the groupset with the shiny shifters I actually do like! From memory not particularly light so a weird design really.

They did not like the design either it seems. The one next year was “normal” again in my memory serves me well. And yes, the Karakoram also had the bling shifters.
As for the paint job. I will post the result
Thanks for the advice