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motorcycle head bolt fix.

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  • motorcycle head bolt fix.

    Recently during a restoration of an old honda motorcycle I had a broken head bolt to contend with. It was broken down low and the break was at a steep angle. Drilling was out of the question and so was milling.
    After looking the situation over I notices the threads were raised on the shank of the bolt.
    I borrowed an idea from another post on here. I reinstalled the block on the crank case, then cut a sleeve.
    I will ommit measurements because they may be subjective to user and engine.
    Rhe O.D is cut to fit snug inside the bolr hole in the block, the I.D is cut slightly smaller than the thread I.D.
    I bade a hole saw/mill with a reverse tooth patern (borrowed from a post about bell repair). The the O.D is to be snug inside the sleeve.
    I made a depth stop to prevent boring into the block. So with all this I was able to bore the bolt out of the block without damaging the threads or block or crank used a dental pick to peel the bolt threads from the crank case threads.
    I appologise for being vague but the measurements will be subjective to the user of the idea.
    My bolt was 15mm thread O.D. with a shank O.D. of 13.5mm the block hole was 16mm on the xrank case the thread O.D. was 15.1mm the I.D. was 14mm.
    The measurements varied between the 8 head bolts.
    I will post pics the nexr time I ise thos process which should be in aboit 18 days when the next bike comes in.

  • #2
    Good fix - I had to do the same thing on an olds cutless sierra ( I think that's what it was called)

    blown head gasket and had a broken head bolt that was severed on an angle, bought the car as a basket case and you could see where the "mechanic" that took it apart tried to drill and got off angle and tore into the block,,,

    so much so that I knew it was either going to be heli-coil time or an oversize bolt.

    briefly gave thought to some kind of fixture I could build to guide a bit in - then -
    threw the head back on and lightly bolted it down with a few to use the head as the guide, but nothing I had (that length) would touch the hardened head bolt so I ended up modifying a cement bit, they have a carbide insert at the end and I spent allot of time on the grinding wheel coming up with a tip that was sharp and would bite,,,

    anyways - got the thing drilled and tapped and installed an oversize head bolt I had laying around from some other engine,

    long story short - car was a mint body and interior - needed a map sensor and threw that on - everything else mechanical was solid, great tires,
    8 hours work and had it sold the next day to a friend of the family and cut the guy some slack - still 25 hundred bucks profit, pretty good day...
    Car held up for over a decade to where the older gent I sold it too could no longer operate a motor vehicle...

    moral of story, sometimes the tools you need to fix things are attached to the thing your fixing...


    • #3
      I remember dealing with a cracked block on a Ford once. It was a 292 "Y" block, that had been bored out to 312 (.060") The block had cracked between #6 and #7 cylinders. The cylinder bores were pretty close together in that area. In fact, I've seen a lot of "Y" blocks crack in the same place. After doing a little research, I settled on "Irontite" steel plugs.
      The crack was cleaned out, and punch marked for drilling, with the drilled holes overlapping slightly. So, some kind of a fixture was needed. I ended up using a 2" square steel block, bored to be a close fit for the drill. It was clamped in place with a clamp head and some bolts from my junk box. Of course, I had to move it for every hole. An old Craftsman corded electric drill was used to do the drilling. After each hole was drilled, an "Irontite" plug was hammered in, to a depth of about 1". The plug was then roughly ground off flush with the deck of the block. Once the crack was completely filled, the tops of the plugs were dressed down even with the block surface. The normal cleanup was next, then the new gasket and cylinder head was reinstalled, and torqued. To insure complete sealing, a small amount of "stop-leak" was added to the cooling system. It performed well. And was still holding when I sold the car, a year later. Of course, an old mechanic told me you can't do that. And, in his opinion, you'd have to weld the block with a "low hydrogen" rod, then grind the crap out of it. I didn't have a welder at the time, so I tried this.
      No good deed goes unpunished.


      • #4
        I've heard "you can't do that" and "that won't work" from mechanics all my life. I believe it comes from a person believing that since they are either not resourceful enough creative enough or just plain smart enough to do some odd task then no one else can do it either.


        • #5
          Iv re-invented the wheel too many times to listen to too many people, confidence is high - they better immediately back it up with a very sound "why" or im off flying by the seat of my pants...


          • #6
            I think I've worn the seat out of mine. My next project on this particular bike os to base grind the cam for more lift.