Nearly everybody who has ever ridden a SOHC Honda CB750 at freeway speeds has lost a left side cover. It’s an affliction they have been cursed with since day one. You may notice all the “customs”, “cafe racers”, and “brats” running around with pod air filters and no side covers. That is because without the factory airbox in place your legs direct high pressure air into the empty space behind the side cover. It has to go somewhere and often times it blows the side cover off.
Because of this left side covers are at a premium. The right side has the oil tank & cap to prevent being blown off, so there are plenty of those around. My current 1972 Honda CB750K2 build is almost done, but I was in need of a good cover on that side. Ebay came thru with a beat up cracked cover with 12 coats of paint on it but 3 good mounting tabs. I had a clean, slightly damaged cover which was missing 1 tab, so we will attempt a tab transplant!
First thing you need to do is get the right glue. I have had luck using flexible parts repair made for things like bumper covers on cars, and my favorite for healing cracks on the back side where they can’t be seen is any of the Goop or even Shoe Goo products. Crazy Glue and Super Glue doesn’t work, J.B.Weld and fiberglass tend to be too inflexible and crack over time. A trip to the hardware store yielded 2 plastic bonder products. Since I needed to fill in a little space, and wasn’t just gluing a broken piece back on I ended up using the Loctite Epoxy Plastic Bonder. Side note though: who spends $5 on glue to fix a $10 plastic lawn chair?
First cut off a piece to transplant, leaving it bigger than the hole you have to fill. Then cut the hole slightly bigger until the 2 pieces are almost exact mates to each other. The CB750 side cover makes it pretty easy. I just cut a straight line where the crease is between the round & flat sections, then 2 small cuts at the ends. The way I did it means a lot of surface area being bonded, which is better if you want it to last.
Sand the 2 pieces until they match with a tiny gap, to be filled in with the epoxy.
Mix the epoxy, spread a little on the edges and just stick it on there. Twenty minutes later…
…and the Loctite Plastic Bonder Epoxy is hard and the bond is so solid you can pick it up and wave it around by the tab you just transplanted. Only time will tell how strong it is, but for now it seems about as solid as if it were never broken at all.
A little sanding to blend the edges, a little primer, some more sanding and some paint and your never know (from this side) that it was ever broken. Its such a shame though that I could not get the last 6 coats of paint off the donor side cover and keep the fabulous candy metallic lacquer underneath in good shape.