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cylinder head guard bolt drill-out


bacos

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So, a previous version of me went to mount cylinder head guards on my wife's rockster... and discovered that the bolts that you'd use were rusted in place.... by twisting them off. Yeah, why didn't I use more penetrating lube first...

 

Life then happened in various unpleasant ways, and the bike sat there for a few years and I forgot about the whole thing. I got reminded of it recently because wife decided to try to ride again. I sent the bike to the dealer with instructions to drill/tap. They wouldn't do it, claiming that it was just too complicated - they'd have to take the heads off and mount them in a CNC machine to do the job. On reflection, yeah, it's probably a pain in the ass job.

 

So it's probably just wishful thinking, but does anyone have any bright ideas or is this another case of "it'd be cheaper to just replace the bike"? (Might have an issue with that though.)

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11 hours ago, bacos said:

So, a previous version of me went to mount cylinder head guards on my wife's rockster... and discovered that the bolts that you'd use were rusted in place.... by twisting them off. Yeah, why didn't I use more penetrating lube first...

 

Life then happened in various unpleasant ways, and the bike sat there for a few years and I forgot about the whole thing. I got reminded of it recently because wife decided to try to ride again. I sent the bike to the dealer with instructions to drill/tap. They wouldn't do it, claiming that it was just too complicated - they'd have to take the heads off and mount them in a CNC machine to do the job. On reflection, yeah, it's probably a pain in the ass job.

 

So it's probably just wishful thinking, but does anyone have any bright ideas or is this another case of "it'd be cheaper to just replace the bike"? (Might have an issue with that though.)

Morning  bacos

 

Depending on what bolts you are dealing with  it can be a real pain & be pretty precise work to drill them out straight then either re-tap or add heli-coils.

 

My standard answer to most questions about drilling out broken bolts in difficult areas is: If you have to ask HOW then you are probably not the best person to be doing the job.

 

Drilling out broken small bolts that are rusted tight in blind holes is not a job to learn on, or a good first time project. In fact more things can usually go wrong than go right when it comes to a job like this. 

 

I have probably removed or drilled out well over a thousand bolts in similar locations & in similar locations in my long life & very few go exactly as planned. 

 

So my suggestion is to find a local machine shop or qualified technician that has done this type of work before. For someone that has done this sort of thing many times it shouldn't be a difficult job. 

 

If you are intent on trying it yourself then we will need some good clear close up pictures of the broken bolts & area around the bolts to give you guidance.

 

Having done many similar projects I don't have a game plan for you until I can see EXACTLY what you are working with & what kind of straight access you have.

 

My usual (but not set in stone)  response to broken bolts that are/were rusted tight is to precision tig- weld on a flat washer over the broken bolt (unless it is broken off below the surface), then weld a nut to that welded on washer. The heat of welding usually breaks the  bolt loose in the blind hole then the broken piece will usually spin right out (well most of the time anyhow).

 

If I end up having to drill the darn thing out  I FIRST determine how deep the blind hole is so I can make a drill depth stop so I don't drill too deep & drill through the bottom of the blind hole (this step is important).

 

Next step is to dill a very a small pilot hole that is PERFECTLY straight & centered as this is the guidance for the next step. 

 

Once I have the small pilot hole that is centered & straight I then switch  to left hand drill bits in progressively larger sizes & core drill the broken bolt out in increasingly  larger steps up to drill size for a tap used on that bolt size. I presume the bolt size that you are working with is 6mm x1 so a number 9 (L/H) drill bit would probably be as large as I would drill with. (maybe not even quite that large).

 

Using L/H drill bits opens up the chance that the drill bit will catch in the broken bolt as you drill then back the broken piece out on the drill bit. 

 

Even IF you manage to drill the broken bolt out to proper tap size you then risk breaking off the tap as you re-thread the hole as the hole will still have pieces of the old broken bolt threads trapped in the existing threads. (so I usually use a small dental pick to remove as many pieces of the old threads as possible)

 

When doing a job like this you need good  common sense, a good feel for something going wrong BEFORE it actually goes wrong, & willingness to quickly change direction as many times as it takes to complete the job without making the situation worse. 

 

 

 

 

 

 

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3 minutes ago, Skywagon said:

Hey DR you left out one of your most sage pieces of advices. No easy outs 😁

Morning  Skywagon

 

Good catch, definitely no easy-out's (better known as easily-broken-off-but-very-difficult-to- remove out's).

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It's gonna be a PITA but you will never know that until you try. Doing it on the bike with a hand held drill is rarely a recipe for success. The part must come off the bike into a vise grip/drill press to get that starter hole centered. Once you have this basic equipment and a lot of patience, you are in control of the problem. Watch some Youtube videos to improve your technique.

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Yeah DR, I *know* I'm not the best person to be doing the job. :)

 

My only concern is that the piece of plastic that saves the lower plug from getting banged/broken off by a rock is also gone; if she drops it and bangs up the valve cover, well, ya know.

 

It occurs to me that I only really need the front location (that bit of bolt sticking out for the bottom would locate that location), and if I can just deepen the hole another 1/8-1/4",  I can put something in the hole in the bracket to create a stud that could sit in the hole; the natural tension in the plastic of the bracket (there's quite a bit of push to get it on) would hold it in place just fine til winter when I can afford to leave the bike in pieces for the weeks it'd take me to pull/reinstall the head and get it drilled.

 

 

One of the up - or down - sides of coronavirus and 100% WFH is that I no longer have the excuse of "I'm in the city and never home enough to work on this stuff" .... so apologies in advance to everyone for whatever dumb-ass stuff I come up with trying to remember how to work on things...

 

 

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Looking at photos, the bolt in the front looks "easy" because the break is indented within the cylinder and will guide the correct size drill bit accurately if you have straight access. 

 

The bolt on the underside seems non-accessible for most drill tools even with the bike on its side. Since it is broken with a stub showing, you might want to try penetrating oil, mild blows with a hammer and turning it with extra large pliers. It is possible that the bolt head was bad but the bolt threads itself might be in better shape. Perhaps spot welding a nut on the exposed threads. I was thinking Loctite red but don't think there is enough to bite.

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39 minutes ago, bacos said:

Yeah DR, I *know* I'm not the best person to be doing the job. :)

 

My only concern is that the piece of plastic that saves the lower plug from getting banged/broken off by a rock is also gone; if she drops it and bangs up the valve cover, well, ya know.

 

It occurs to me that I only really need the front location (that bit of bolt sticking out for the bottom would locate that location), and if I can just deepen the hole another 1/8-1/4",  I can put something in the hole in the bracket to create a stud that could sit in the hole; the natural tension in the plastic of the bracket (there's quite a bit of push to get it on) would hold it in place just fine til winter when I can afford to leave the bike in pieces for the weeks it'd take me to pull/reinstall the head and get it drilled.

 

 

One of the up - or down - sides of coronavirus and 100% WFH is that I no longer have the excuse of "I'm in the city and never home enough to work on this stuff" .... so apologies in advance to everyone for whatever dumb-ass stuff I come up with trying to remember how to work on things...

 

 

 

 

 

 

Afternoon bacos

 

Depends on how accurate you want to be & what you expect as far correct goes.

 

That broken bolt that is sticking out would be a real good candidate for welding a washer/nut on as it would probably come  out fairly  easy that way. If you fool around & mess with it using vise grips or other ways trying to grab it  trying to  get out you will probably mess that little stub up then you lose the option of getting a good weld to a washer. A welded on washer then welding a nut on the washer is probably the most practical way to get it out easily. 

 

That bolt is rusted in there firm enough that it broke the bolt head off so it won't come out easily (or at all) without using heat. Welding on  a washer not only protects the alloy head but at the same time the welding  is super heating the bolt to release it from being corroded in the hole.   (at least that is the way I would do it & I have done  plenty of broken bolt removals of steel bolts from alloy holes)

 

On the front one broken off below the surface that is definitely a drill out then re-tap. But the exhaust is in the way so you would either need to remove the exhaust or use expensive long drill bits. (L/H drill bits are your friend here but long L/H drill bits are expensive. 

 

On the front  & rear you could drill the bolt on center, best you could, to 3/16" then drive in 3/16" roll pins That would hold the guard in place if you get the lower bolt repaired to hold the bottom on tight. Just don't drill too deep as the holes are blind holes.

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No welding kit. Dad had welding kit, but for whatever reason he never taught me how. Mom never taught me Japanese either. I regret both of those things.  :( and no LH bits either. Might oughta get a set.

 

Turns out I do have a drill bit extension. Grabbed a very small drill bit to see if I could freehand it. Figured if you keep the hole really small, and aim within the mass of the bolt, worst that happens, the bit starts to wander, and you give up before you start hosing up alloy. Center punch, drilled a 1/16" hole into the center of the bolt, marveled for a bit that I got away with it, bored it out to 1/8" (again figuring to keep it within the mass of the bolt), tapped it as a #8 (since I only have SAE taps), created a small bushing out of a piece of 3/8" rod for the guard so the #8 "fits".

 

The front and rear hold the guard well enough that the bottom stays in place well enough to guard the spark plug (the bottom hole sits on top of that stub, which locates it).

 

It's not pretty and I'm not proud of it, but it'll do until winter when I can afford to take the head off and do a better job. In retrospect I should have waited and bought the LH bit set to see if I'd get lucky - not like I was really in a hurry. But I suppose that's how we learn.

 

thanks for the info, learned a lot just thinking through what you said.

 

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Find a good welding or muffler shop

show them the pictures and see what thy say

The lower one is definitely doable with the "weld a nut on method" just remove the tank  drain the oil  and lay the bike on its side

The front one is not a huge issue either

Muffler shops deal with this frequently

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