Sheared header bolts | GTAMotorcycle.com

Sheared header bolts

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tricky

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Sheared not one, but two header bolts. One is about 1cm out of the hole, and I dremelled in a deep slot in it to try to manipulate it with a flathead screwdriver.

I sprayed it with PB blaster, and tapped it a bunch with a hammer to try to shake all the crud in the threads loose. I heated the bolt with a propane torch. I think it budged a bit when I tried to torque it with the screwdriver... leading me to believe that plenty of PB blaster, heat, prayer and clean living will get that bolt out.

The other is not so good. It is closer to flush with the header. I failed at dremelling a slot in it, and there isn't much to grip on to.

Ideas?

How does one go about drilling out a bolt without ruining the threads on the header?

The area isn't exactly easily accessible, as the engine is still in the bike and I'm trying to avoid removing it
 
Depends on the type of bolt or condition.

They are usually steel,...I like to remove the rad for stuff like this. Drill a hole for a extractor bit - and get the bolt extremely hot.

Use a ratchet with the extractor bit and feel the threads....if it is budging go ahead with it....

Post pictures - we might have more ideas.
 
Even if you wreck the thread you can use a thread insert to make it as good as new, so don't worry too much.
 
frekeyguy said:
Depends on the type of bolt or condition.

They are usually steel,...I like to remove the rad for stuff like this. Drill a hole for a extractor bit - and get the bolt extremely hot.

Use a ratchet with the extractor bit and feel the threads....if it is budging go ahead with it....

Post pictures - we might have more ideas.
Click to expand...

Thanks, both of you.

I ordered an extractor set, I'll get to it next when my schedule dies down. I'll try to snap a picture before then.
 
Left handed drill bits are great for this as they often bite enough to turn the broken piece out...and if not you have a hole for your thread repair insert ;)
Good luck!
 
AWW Dude that sucks!!!

I broke a header bolt on my car one time, I snapped it in half trying to get it off. I managed to get the entire header off and put the new one on. I just JB welded the broken peice back on LOL.

This wont help you in your situation, But I feel your pain! Goodluck man!
 
Times are tough. Tried two different screw extractors, none worked. I tried drilling them out, and it worked for the most part with 1 bolt. Made a mess of the other hole... some of the bolt is still left in there, and I drilled into the cylinder head itself at some funky angle, as I was trying to wrestle the drill around the frame.

Taking off the cylinder head soon to do this right. I'll either drill and tap new holes (will have to go to M10 from M8 bolts with the enlarged holes), or I'll drill and do helicoil inserts.

Gotta check my valve clearances anyway, right? :rolleyes:
 
I just noticed what bike this was on. Can you take pictures, so I can learn from your adventures?
 
In the future remind me to warm the engine before breaking any screw loose. I think steel screws on aluminum blocks are a pain.

My advice? Get an impact driver.
I remember replacing all the screws on my carb with Brass after I suffered
 
TwistedKestrel said:
I just noticed what bike this was on. Can you take pictures, so I can learn from your adventures?
Click to expand...

Will do, I will probably be heading to the shop today to try to get the cylinder head off.

For you and RockerGuy, just be mindful with these header bolts... I foolishly kept torquing it, and it didn't even take that much to shear them. The moral of the story is if you encounter any resistance, stop, hit it with PB Blaster or Liquid Wrench and keep working it back and forth carefully.

And yes, RockerGuy, I have already had the pleasure of dealing with those soft metal JIS carburetor screws. I already swapped them out for proper bolts.
 
Got the cylinder head off. As you can see, two of the four manifold bolt holes are in rough condition. The inner one has maybe 25% of the thread left, the other one is a complete mess. Part of the bolt is still in there, and the drill bit went in at an upwards angle and drilled into the cylinder head itself. This is what I get for trying to fix it when it was in the frame.

Once the cylinder head was off (I found the Clymer's manual to be very good for this; also the top-end rebuild series starting with this video https://www.youtube.com/watch?v=6X0VwcdZq7M), I created a list of parts and tools I would need to complete the job. All in all, this repair will probably run me about $200.

I will need to replace the cylinder head gasket, and I've also read mixed reports of whether or not I will need to replace the cylinder base gasket. Once the cylinder head was loose, the cylinder base was able to separate from the crankcase. I'm not sure if the old cylinder base gasket in there will create a proper seal when I put it back together.

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Think of this as a $200 lesson. The next time you work on a bike you'll be more confident & you will get to reuse your tools
 
My worst fears were realized when I extracted the rest of that screw and surveyed the damage. I had drilled into a passage above the manifold hole. This passage contains oil when the engine is running, it is plugged at the end by a bolt. I believe these passages are due to the manufacturing, it does not transport the oil anywhere.

So, now I need a new cylinder head, or I can try to seal the exhaust manifold bolt when it is in place to prevent the oil from leaking out. I'm not sure how I would seal it, thread sealant or gasket maker I suppose.
 
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