Topic: New guy, new project - tank modification

[Hutch]

I'm planning on what I'll call an "elegant" modification to my 1982 CB650SC.  I'd like to eliminate the tab on the lower portion of the tank so that the tank has a relatively straight line across the bottom.  This will be paired with some custom side guards and a rear cowel I'll fab up.  I wanted to throw this out to the forum for ideas on how best to modify the tank.  My initial thought was to leave enough sheet metal so that I can fold over the flaps rather than make a small patch.  Does anyone have any thoughts/ideas/experience cutting a tank?

[calj737]

If I understand you correctly, you are intending to remove or at least, re-fold the factory pinch weld? To eliminate that weld, you'd have to either: extend the metal to fold it over, or cut it off and re-weld the sides directly.

The latter is a great deal of work to get right. Very possible, but at lot of work. Others have taken to replacing the tank with a custom, new tank absent of the weld in lieu of that metal/welding work.

Another idea to consider: re-install the factory metal trim but paint it the same color as your tank. Scuff off the chrome plating, then prime and paint with tank color. This will "hide" the edge better and eliminate the work.

If you are adamant about adjusting the lines of the tank, you'll want to be very good at metal shaping and TIG welding to guarantee the alignment and prevent leaking.

Keep us posted!

[Hutch]

I don't plan on removing the entire pinch weld only that portion of the tank marked in yellow on the original picture.  This crud diagram might help explain.  Basically I would make a small vertical cut (red line) after cutting of the portion of the tank I want removed.  Rather than adding a piece to fill the gap, I would fold over B then A after some trimming.  There would be overlap, so the next step would be to cut through both A and B after they're folded over to create a butt joint/seam.  I expect the resulting joint to be 4-6 inches plus any collateral damage to the factory pinch weld.  I'm OK with the tab from the factory pinch weld visible on the rest of the tank, although I may end up gently folding it over.

Love to hear from some guys who cut into tanks.  I'm trying to keep the effect on the factory weld to a minimum.  My hope is that the small new welded seem is not visible on the underside of the tank, although I'll hope to clean it up enough so that its not evident anyway.  I'm OK with the cutting and shaping, but plan to find someone far more skilled with a tig welder to make sure the tank seals properly.