Topic: 75 CB550F - Are missing bolts in the oil pan a crime?

[Mr B]

Hello,

During the past weeks I did some work on my '75 CB550F. (New piston rings, gaskets, contact points, condensors, fork seals, stearing head bearings, clutch, brakes, lots of rubber parts, cylinders honed, valves lapped, carbs cleaned,...)
Almost done with the "major maintenance" and all went pretty well, until...
One of the last things I did was removing the oil pan to replace the rubber seal. I broke off all 10 bolts... aheum
Normally no problem, just some work, but I managed, with my removal set for broken bolts, only to remove 7 of them... (drill a small hole in them, left hand tap and so on)
For the three remaining, some things went wrong (also out of frustration). When drilling, the drill went into the aluminium... for one bolt, the carter broke to the outside, for the other two, it is just a mess a and everything seems to melted in each other, resulting in broken drill bits still stuck inside. It is a crime scene. As it is a hard place to reach and I was having a bad day, I really ****** it up. (I should have done it better, but now the situation is what it is, I cannot rewind time.) I do not know it if even a helicoil could solve the problem and I am not equipped for welding.

Therefore, is it really a problem if some bolts are missing in the oil pan? Will it leak oil, or will it just sweat a little? Does anyone have experience with bolts missing in the oil pan?
(It is not a rebuild or super clean bike, the complete disassembly will be something for the future.)

Thanks a lot for the advise.

[RAFster122s]

If you can find someone whom has experience repairing aluminum castings you may be able to salvage things by heating and cleaning the oil from the case where you have the damaged areas. First extracting the broken bit and broken screws. Lay cardboard and some blocks down and put the bike on otsside so you can access the bolts and areas without having to work upsidedown. Tig welding the holes and then drilling and tapping holes in the damaged three areas. Breaking off an ez-out you want to avoid at all costs.
Pulling the motor and removing the bottom case a machine shop can do a clean repair.

Time serts are going to be a better repair if you cannot redrill and tapping the holes.

Worst case you tear the motor down and transplant it into another set of cases if it goes pear shaped.
But, you will want to do a rebuild if you go that route.

Find it surprising that you sheared all 10 bolts. Were you tightening instead of loosening the bolts? Easy mistake many have made when working upside down.

[754]

You should post your location.. help might be nearby...

[JLeather]

I suppose that if it doesn't leak there's nothing else that missing bolts could cause.  If you had just one missing you'd probably be ok, but I'd expect 3/10 to cause a leak and a leaking oil pan goes right onto the back tire (not good).  I would yank the engine and have it fixed.  Taking the engine out IMO will save you in the long run when you start paying someone to weld and tap those holes.

[754]

IMO the best way is make a drill guide out of at least 1/2 steel plate..use oil pan to lay it our.
 Holes smaller  than the bolt. Then drill thru the CENTER with a smalk CARBIDE DRILL.  ...right thru, then you can get penetrating oil in from the back.....NOW THAT YOU ARE IN THE MIDDLE, it gets way easier.
  Can be done with bike on its side.,