Author Topic: Broken bolt on crankcase oil pump cover  (Read 669 times)

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Offline AdminPete

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Broken bolt on crankcase oil pump cover
« on: November 27, 2008, 06:05:46 pm »
Anyone had any experience extracting one of these when it has broken off flush to the crankcase?  I've attached a photo of what I'm talking about.
I've read up on extractions in general and am looking for a real case scenario.

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From: bsa_C11G Sent: 06/02/2007 21:50
It all depends on the location of the bolt.
I have a Dremmel so now days my favourite method is to put the diamond bur in and make a small locator hole in the center.
Swap that for a drill and drill down at least 1".

From here I can go a few ways depending upon just how critical the bilt is and what are the consequences of stuffing things up.

In a really critical spot, I go the bigger & bigger drill route till I am nearly at the root depth of the thread. If it is still stuck fast then out with the Dremmel again using the parrallel cutter and take the hole out till there is nothing left of the bolt but the threads. Usually you can then just pull the last spiral out but on a few occasions I have had to resort to using a tap to chase the last bit of the bolt out from in between the threads.

In a less critical spot I tap the new hole with a left hand thread and fit a loose left hand bolt in and extract it that way. It needs to be a bit loose so that the broken off bolt can "collapse" a bit back into the hole.

In a "dosen't matter" suitatuion I go for the easy outs.
The problem with easy outs is the fact that they are tapered and as they bite & dig in, tend to spread the bolt ( like a rivet) that you are trying to remove thus making the broken bolt even tighter in the hole.

I always start with the Dremmel because the broken off end will never be flat and you really need to get the hole as close to dead center as possible and drill bits will tend to wander all over the surface following the surface contour.

Bike Beesa

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From: bsa_C11G Sent: 07/02/2007 08:46
Had a look at your pickie.
That is an easy one.
Drill a series of holes in the center of the broken bolt at increased diametes till you have a hole that is 1/2 to 3/4 of the diameter of the broken bolt and then go with an easy out
\Bike Beesa

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From: floydpiper Sent: 08/02/2007 01:28

First, Trevor has given you good advice.

I would simply add that if you are going to go with an easy out, spray penetrating fluid (It DOES get in), and VERY carefully heat the area OUTSIDE the bolt with a propane torch. Be careful because you are dealing with aluminum; but if you just wave the heat back and forth around the area you'll be fine.

You will NEVER get that thing out with an easy out without using heat, no matter what anyone tells you. In fact, without heat you'll likely break the easy out in there, and then you will be in Fubarville.

The only other alternative is Trevor's suggestion of drilling away at it until you can practically pick the old bolt out of the threads. I do it that way when I am dealing with brass bolts broken inside aluminum Amal carburetors. And carbs have much thinner aluminum than a crankcase, so please believe me that you CAN heat it up with a torch. JUST BE CAREFUL, that's all. You want to get it just barely too hot to touch, and no hotter than that.

You know that part of your brain that says: "Let me heat it up just a little more."


You need to ignore that part of your brain!

Good luck.


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From: shuswapkev Sent: 11/02/2007 20:21
  for these types of drama, try heading into your engineering supply and picking up a few left hand drill bits. they turn backwards  ...first they are new ,n sharp and can only be used in these situations and best of all when they do catch (and often do,) will unscrew your bolt leftovers.  the dremel tricks above and the heat  are where your success will be found.    played with too many japanese sodermikels

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From: FYoF Sent: 23/02/2007 04:13
THX folks, setting up for it, warmed it up today and it leaks less, preparing for extraction.

sunny days a 'commin