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 Sheared Engine Mounting Bolt

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Guzzi Cat
Biondino
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PostSubject: Sheared Engine Mounting Bolt   Wed May 17, 2017 2:39 pm

I just noticed that the front left side engine mounting allen head bolt has sheared (M12 x 50mm) on my Stelvio. Evil or Very Mad  Has anyone encountered this on the GRiSO or Stelvio before?

I was having a look around when the bike was on the lift for a tyre change and spotted that the bolt was missing, It is sheared off flush with the engine block and I don't know how long it has been like this as I never noticed it before!

I am hoping that I can drill it out in place (through the frame where the bolt is missing) and re-tap it to take a new bolt. If any one has done this before I would be interested in hearing how it worked out? Does the bolt go right through the casting of the alternator belt housing or is the bolt threaded into a blind hole in the casting?

It may be prudent for members here to do a visual on their own bikes to make sure that no engine mounting bolts are missing (broken) Exclamation

Thanks,
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Pete Roper
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PostSubject: Re: Sheared Engine Mounting Bolt   Wed May 17, 2017 3:07 pm

Yeah, Wyno's GRiSO had the same problem. We just swapped out the timing chest cover during the rebuild and will fix the busted bolt when we get round to it.
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guzziownr
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PostSubject: Re: Sheared Engine Mounting Bolt   Thu May 18, 2017 5:02 pm

Hey Cat, it goes straight through.  I stripped mine and had to pull off the engine cover and put in a TimeSert.  I bought a used cover from a Norge to use as a practice piece.  Very similar but not identical to the GRiSO. Timesert was easy, even for a novice. I bolted it to a drill press to keep it straight.

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Guzzi Cat
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PostSubject: A Ball Breaker but its done   Sat May 20, 2017 1:43 pm

A right bollox of a job but turned out good in the end, I will give a few details that may be of help to some other poor misfortunate Laughing

Well I assembled all the bits that I figured may make the job a bit easier, I got a buddy of mine that has a lathe to turn down 3 guide bushings 12mm OD, each with a centered hole to guide my drill bits, 5mm, 8mm and 10mm. I even got left hand drill bits in the hope that it might spin out (NOT A CHANCE) and a couple of 12 x 1.75mm taps if I couldn't get the broken bolt out.

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The plan was to try and line the frame mounting bushing and the timing chest as centered as possible and then drill a hole with the smallest of the left hand bits (kept centered with the guide bushing) and then to hammer in a spline drive and try and twist out the bolt (No JOY) Sad

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I then moved up to the 8mm left hand bit and hammered in a spline drive, it really got a good grip and I tried to turn it with a socket (NO JOY) and then an air impact gun for about half an hour (NO JOY) Sad  and then I went Nuclear and tried a 3 ft breaker bar (thinking that the splines would just round out the hole)" WRONG AGAIN". Crack and there goes the the top of the spline drive and it is now buried in the hole Evil or Very Mad (I used spline drives because I didn't want to risk breaking an Easy Out)

I thought I was screwed and was trying to find a small long Dremel grinding tool long enough to grind out the broken spline. Idea  But thankfully I calmed down and studied all the options and realized that I should be able to drive it out from the inside of the timing chest (thanks Guzziownr for the picture of your timing chest) so I took of the cover and punched it out cheers

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At this stage I realized that that bolt wasn't going to move so I drilled and tapped it (taking great care not to break the tap)

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It worked out great in the end and I stuck in a new bolt temporarily until the new one arrives from TLM. cheers  cheers  I know that I could have took of the timing chest but tried to avoid it if I could and was afraid that the other mounting bolt would shear off as well Exclamation

Check your mounting bolts because I have no idea how long that has been sheared study
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Bill Hagan
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PostSubject: Re: Sheared Engine Mounting Bolt   Sat May 20, 2017 4:51 pm


Impressive.

I am torn between being awestruck at what you did ... and annoyed that I couldn't have done that with all the tools provided in an a/c shop, a detailed video ... AND Pete Roper on call. Rolling Eyes

Seriously, nice work ... and, yes, I'm going to check minre.

Bill
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Pete Roper
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PostSubject: Re: Sheared Engine Mounting Bolt   Sat May 20, 2017 5:30 pm

Nice work. I still think I would of pulled the timing chest but it proves that it can be done. Well done. Thumbs Up
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