Topic: cb550 top end, new threads for middle front bolt

[BigBird]

I was torquing down my top end [first 10lb ft, then 15] the last bolt at the middle front overturned and the thread in the aluminium cylinder block was gone with bolt intact. I can't thread it without taking the cylinder block off again. I left the engine torqued 24hr ago, and now I realise i have to take it apart again. Is it necessarily bad for the bottom and head cylinder gasket? They were put in dry and clean.

Thanks in advance!

[CBGhia]

It won't hurt anything.  Take it apart and put a case saver insert or whatever. 

[DaveBarbier]

Isn't the recommend torque for those bolts 8 ft lbs? I just use a 1/4" ratchet and choke up on it then give it a firm twist. But again, as everyone knows I have baby hands.

[alacrity]

It's possible you can get a bit extender to allow you to drill tap and then fit a helicoil (or similar) without pulling the head back off.   Try sliding the bit extender into place, then fitting the bit into it?

[strynboen]

can you not use a vaccumcleaner(støvsuger)..and drill and tap helicoils in the 4 holes..

[MickB]

Plug all the openings with rags, and tape over the bearing surfaces and use a helicoil and as you use the tap have a mate with a vacuum cleaner to suck up all the metal shards that come out of the tapped hole.
It works, I had the same problem with my head and didn't want to have to pull the cam out, I had rags blocking the bearings and other openings, used a hand held vac and no problems.

[BigBird]

Thank you very much for response. I pulled the head off, tapped a size up and put in a steel thread that matches the old bolt. Head mounted and torqued for re-torque and startup in a few hours.

Will now be skimming through build threads to look for first startup tips