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Old 29th May 2019
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Quote:
Originally Posted by herostar View Post
Hello everyone!

I had two exhaust studs break off, one in each cylinder head, so I'm going to need to remove the heads to get the broken studs extracted/replaced at a machines shop.

My question for you all: What else should I be doing while the heads are off? I'm not looking to go deep porting/polishing or anything, but am curious if there are "normal" maintenance things I should take care of while everything is off the bike.

FYI this is for a 2003 XB9R

Thanks in advance for your help!
If you get the proper tool for drilling out the studs, you don't need to pull the heads. I think you'll be surprised how easy it is. Just go through the procedure for rotating the motor down, which is described in the service manual. You'll have enough access to do the job.

My advise is don't even waste your time trying to unscrew the old studs. They're going to be stuck in there like you can't believe and the chances of unscrewing one are slim. The studs are an interference fit thread on the head side. That means they're designed to bind up in there, and they do a mighty fine job, too, especially after 16 years of being heat cycled. Not to say it's never been done, but it's just unlikely you're going to unscrew a broken off stud.

And whatever you do, don't let an easy-out get within 10 feet of your bike. I can't begin to tell you how many heads have come into the shop with a broken off easy out embedded in an exhaust stud. Now the only cure is carbide end mills, which are expensive and easily broken. An easy-out has about a .0001% chance of unscrewing that stud and a 99.9999% chance of breaking off. Don't go there.

Here's what you want:



The drill jig works slick as hell. It sits in the pocket where the exhaust gasket goes, that aligns it. You use the good stud to bolt it down. Now you just drill with a 1/4" drill bit. The jig makes it go straight through the stud. When you're done drilling, you'll have a hollowed-out shell of the stud left in the head, but it generally comes out pretty easy. Often you can do the whole job with little to no damage to the threads in the head. Just remove the hollowed out stud and screw in a new one. Maybe chase it with a tap first.

I suggest replacing it with the factory stud, because aftermarket ones don't have an interference fit thread on the head side. The interference fit thread is what keeps it from coming out of the head when you remove the exhaust. Loctite red isn't going to be effective there, it's too hot.

You may be able to find other brands of this drill fixture cheaper than the above, too, maybe someone will chime in with a link.

The reason the studs break is partly because they get fatigued over the years, but also because of exhaust mounting issues. To the extent the exhaust is allowed to move independently of the motor, it's flexing those connections to the heads. Often a poorly mounted exhaust will cause the nuts to loosen up from this flexing. I've seen guys use locking nuts to keep them on, but that's treating the symptom, and really just making it more likely to break a stud. The root cause of the issue is the exhaust mounting to the motor.

Back in the tube frame days, this was just a terrible issue on Buells. Buell finally came out with an updated mount - the one that attaches the front of the muffler to the motor - that was considerably stiffer. This about 90% fixed the issue, failures became much more rare.
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