Topic: Frame drain holes. How important? Pro's and Con's

[Jerry E.]

My CB750 K3 has no drain holes in the frame, although I hear there should be some from the factory just in front of lower/front engine mounts. Should I drill some? My frame is solid, no rusty area's. I also just installed a "Gordon Frame kit", and the inside of the frame tubes I cut were perfect, no signs of any corrosion. Should I put a hole in my frame, opening it up to the elements? Opinions?

[phil71]

it has made it 39 years as is, and you sound like the careful sort.. let it be.

[lucky]

If you can keep the tubes closed up no air can get inside, so no corrosion would be possible.

[HondaMan]

They are vital. Check closely around the section of the frame where the front lower bolsters are: in the late K2 a hole was incorporated there to vent things. Before that, most of the frames had a hole drilled right into the bottom of the frame right there, each side. Many are painted over (or corroded in, with road grime) and invisible, so poke around to see if yours is there. If not, drill one each side, just ahead of the bolsters, don't be surprised if water comes out. I do this with every 750 that comes to me: many were not drilled at the factory, and most of those have rust inside the frames. A 3/32" hole is adequate: spray a bit of CRC or Liquid Wrench (don't use WD40, it attracts moisture) up inside the frame and let it drain. This will pull out most of the condensation.

Some of the worst culprits were the later K4 thru K6 frames.