Topic: Broken bolt hole

[VTCBike750]

I wish I knew how to weld.

So Im going through my K2 and stumbled on this previous PO repair. Broken bolt hole for the points cover with silicone. What are my repair options?

[Don R]

 I'm not sure how thick the metal is, could it be drilled deeper, tapped an get a longer bolt? Maybe also build up with jb weld and tap that?

[spotty]

maybe rather than fill and tap with jbweld, how about putting a oiled bolt into whats left of the threads and then build up the jb around that, when its set you should be able to unscrew the bolt, keeps it properly lined up and saves the hassle of trying to drill and tap a new hole in the right place

i'd oil the bolt so the jb doesn't stick to that when it sets

also you'll have to clean up the silicone really well to ensure the jb adheres properly

[jgger]

Spotty is close, just use epoxy putty. Comes in a stick, knead it then press it into place. Won't run and goes off fast.

[pjlogue]

I had a lower timing cover screw break off.  I ended up drilling it out and re-tapping the hole.  I believe the hole goes through the casting and is open on the back side.  You can do one of two things.  Clean all surfaces real well and use JB Weld and drill and retap or clean it up and see how much is left of the threaded bore.  You may be able to use a nut on the back side of the hole with a longer screw and not mess with trying to fill-drill-tap. 

-P.

[DaveBarbier]

Perfect candidate for jbweld or a similar product. And yes, put a screw in the hole coated in a LITTLE bit of anti seize and form the jbweld around it. Make sure the area is very clean first. Remove the screw before it sets up all the way. Then run a tap in the hole to clean it up. You’ll be done in under an hour.

[PeWe]

I have used JB weld for same problem as I described in your build thread.  http://forums.sohc4.net/index.php/topic,181076.msg2098230.html#msg2098230

There was some threads further in that was complete.
So I used a longer M6 bolt sprayed with teflon spray that dried, aligned it correctly and kept it aligned with block down missing piece up, a jar parked against bolt that could not move and filled the gap with JB Weld.

Bolt helped to shape missing threads. I needed to add JB Weld a few times to build up the thickness.
It should work now for the ignition cover. Not tighten too hard. Use long bolt filling the entire thread depth.

Surface filed flat after photo was taken. M6 tap carefully screwed down to bottom. Beginning of hole coned slightly by hand using a 10mm drill.
I think it will hold up if not overtighten that M6. If it crack I'll build up more JB weld, drill and tap for time-sert thread insert. The aluminium is very thin here.

[VTCBike750]

An overwhelming recommendation for JB Weld. It is the easiest and cheapest fix for a bolt that doesnt seal against oil and takes very little torque to do its job. Ill be honest, not overtly excited about the idea of using JB Weld. Id like to find a better solution. That's just me.

Been looking into TIG or MIG welding and may call around town to see if anyone can do it. That just seems like a lot of work, time, and effort for a bolt hole that doesnt seal against oil and takes very little torque to work. First have to weld it, then drill, and tap.

For the interest of education, experience, and doing something new myself, what about brazing with Aluminum repair rods? I've seen a few things on the forum about it. Probably a better repair than JB Weld. Has anyone tired that? I read about it on one of Terry's posts:
http://forums.sohc4.net/index.php/topic,165561.msg1996006.html#msg1996006

[rotortiller]

Why not clean the hole out and glue a threaded insert in with JB weld?

[PeWe]

The missing alu look like much less damage than my block. It look like plenty of good threads left.

[PeWe]

I had another look at my JB Weld fix of that broken hole.
If a Time-sert could improve. I do not think so.

JB Weld Epoxy is really good stuff!
It has hardened really well, bolt sit tighter in this thread than the other not broken.
When case is painted, this repair will almost be invisible.

[kerryb]

I can't speak for jbweld, but I've been very pleased with the results from epoxy putty (PC-7) on similar repairs.  Suggest an oiled screw and build up around it with E-putty.

[754]

I have used Devcon a lot on fibreglass hole filling, it's very tough, but pricey.

[scrambler]

I`d use JB weld only if you are not intended to tear down the engine. JB weld will fix it for now for sure, but next time when splitting the cases I`d get it done properly by welding.

[PeWe]

My cases are apart. I see no reason to weld that thread. No structural importance.  Not worth the risk welding it that might look bad outside.

Different with cracked case like after a drive chain. Here only part of the boss for ign cover bolt thread that now is fixed