TurbineBlade

I have an older miyata with stem shifters, a boss on the downtube to fit the cable housing, and a boss on TOP of the right chainstay to fit the RD end loop.

However! There's no plastic guide under the bottom bracket (obviously because the next housing stop is on TOP of the chainstay) and there's no brazed on, half-moon type guide above the bottom bracket - nor is there a pulley or anything.

Any ideas here? I'm not opposed to drilling the bottom bracket for a plastic cable stop, but then I'd have to deal with the boss on the chainstay.

Recommendations? I tried using a long piece of housing to route the cable over the bb and toward the chain stay, but it bends like a SOB and just doesn't seem quite right when shifting. Plus it requires zipties and looks pretty stupid.

Thanks for any help

LesterOfPuppets

You'll need a guide that clamps onto the seat tube. There are two common types depending on your front derailer.

Front derailer with just a pinch bolt, but no cable stop need this type: (I haven't found any cheaper yet, surely they're out there somewhere)
https://www.lickbike.com/productpage....=%270567-00%27

Front derailer with a cable stop needs this type:
https://www.loosescrews.com/index.cgi...d=282969313384

FBinNY 

You could also mount a seat tube clamp on pulley of the type used for 3-speed internal hub cables. Anything that mounts above the bottom bracket to make a turning point for the wire will work.

BTW- many bikes of similar vintage to yours have 2 bosses, one near the base of the down tube, and one on the chainstay near the bottom bracket ans use a short section of housing to make the turn. If you see two unused bosses, that's what they're for.