Topic: Exhaust header flange bolts sheared off

[DammitDan]

When I got my engine that I ordered off of Ebay from UPS, it came with several things broken (note to self: DON'T EVER SHIP ANYTHING HEAVY THRU UPS).  The clutch cover and valve cover I had replacements for, but I also found that the #1 header flange bolts were sheared off in shipping.  And being over-excited about getting the engine, I unfortunately tried to drill them out to install helicoils. 

Unfortunately the drill wanted to take to the aluminum more than it wanted to drill the steel bolts, but I managed to get one installed (although dubiously).  The other wouldn't cooperate.  I got angry.  I kept drilling.  I pretty much ruined any chance of installing a helicoil on that side (note to self:  ANGER IS THE DEVIL).

So, now I have the #1 header held on with only one flange bolt.  It seems to be doing OK, but I noticed a good amount of exhaust coming from around the seal, which obviously is a bad thing.  Question is, what should I do?  Try to fix it another way?  Find a new head?  Keep riding?

It's a 1982 CB650 standard with an SC engine.  Runs like a dream after it heats up, good pull even past 7k, but it's the heating up part that is kinda bothersome.  It will bog down and sputter out if I don't keep a hand on the throttle with the choke full on.  This may also be attributed to carbs (I get some popping and gurgling at idle, and even more when downshifting) and I have yet to clean those out.

Thoughts?  Opinions?  Pointing fingers and laughter?

 - Dan-0

[oldbiker]

If you or a friend have access to a lathe, turn up a two diameter stud. ie. a stud having a short length of say 10 mm thread to go into the head and a longer length of 8mm to attach the header. Then tap the damaged hole in the head to take the fatter part of the stud. I have seen a repair like this last years.

[bryanj]

Try a "Keensert" if there is enough metal arround the thread

[KB02]

Worse come to worse, you could also take the head off, bring it to a VERY EXPERIENCED WELDER[/i][/u] and see if they cold refill the whole that was left so that it could be dilled out and tapped to the propper spec. I highted VERY EXPERIENCED WELDER[/i][/u] because any VERY EXPERIENCED WELDER[/i][/u] will know that aluminum will warp and melt and might cause more damage to the head in this process. If they know what they are doing, they should be able to do this without causing any extra  damage to the head.
I had the same problem with a bolt on the head of my '76 750. Except it was one of the #4 cyclinder header bolts. What I ended up doing was cutting it off at the base and drilling out the center of it with ever increasing diameter drills untill I got it to a point where I cold tap it out to the proper spec. It did, however, take me four day and allot of trying other things to get to that point. You're right: Anger IS THE DEVIL

[Tim.]

My friend had a similar problem with his 750K7.  One of the threaded holes for the exhaust bolt on cylinder 2 actually broke - a chunk of the area broke off.  Anyhow, we had our heads into a machine shop for valve work, and they built up the area with new aluminum and tapped it.  Worked like a charm.