My bike is a 1980 R100. I've had it for a year now and have been slowly fixing all the little problems it had when I got it. One that I haven't addressed is the left hand valve cover stud (the long one through the center of the valve cover) is stripped where it goes into the head. This isn't much of a problem as the two small studs on the sides hold it securely enough, but when I park it, it drips a tablespoon or so of oil from the bottom and onto my garage floor. I would like to fix it, but don't know what options exist. Does someone make am oversized stud? The stock one is (I think) 8mm X 125 pitch. If someone made a stud that was 9mm on that end, I could just ream out a new thread and install a new stud. I don't know where to look tor this. If an oversized stud doesn't exist, what would the collected wisdom here recommend? Helicoil? TImesert? I have helicoiled spark plug holes on VW motors before so I have a feel for what is involved but have not done this before on a head like this and wonder if it is the same kind of process as this is a "blind" hole that doesn't go all the way through.
Thanks,
Tim
I'd also say Helicoil because they require the least base material. KeenSerts, SpeedSerts, and the like can require massive amounts of material that simply may not be there. I've purchased the complete HeliCoil kits very inexpensively on ebay with just 1 or 2 of the 20 supplied coils missing.
I agree, using a machine tool to get the hole straight is best. But rather than remove the head for a single stud hole I might be tempted to reinstall the valve cover with the outer studs and use the central hole as a guide for the tap. The idea is to get the valve cover back on, and the valve cover will be the ultimate judge of whether you succeed. Loading the HeliCoil tap with grease will capture all the chips and keep them out of the engine.
Good luck.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
The gents above are giving the correct advice, IMHO. I actually recently bought a 1976 R90/6 with exactly the same problem. From what I hear it's pretty common. I came across a "fix" which I'm going to try shortly, only because thie nut on this stud doesn't require a ton of torque (in fact, very little) and also because I'm a little nervous about attempting a helicoil fix without doing it "right", I.e., pulling things apart and making sure each operation is squared up.
The product I'm referring to is made by Loctite and it's called Stripped Thread Repair. It s designed expressly for problems just like this. You might want to check out their YouTube video and see what you think. Full disclosure, I haven't done it yet, but will try soon. I think it's worth a shot and isn't irreversible if it doesn't work.
My 2 cents...
After my last valve adjustment, the center bolt on my RH cylinder felt a little soft under the torque wrench. I may be taking my own advice before too long.
:pinch:
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
Had the same issue years ago. What I did was to go to a European Car Repair Shop and they suggested a Product called "TAP-LOK INSERTS". At the time the closest size to a M8 X 1.25 thread that I could get was a 5/16 - 18. The box instructs you to drill a 7/8" hole then thread in the TAP-LOK INSERT which cuts its own thread into the Head. Then the Stud was retreaded to 5/16 - 18. Would imaging that you now probably can get this in a M8 X 1.25 now. Just had a look on line...Check out a product called "key-sert" It comes in metric sizes in different metals.
Everyone will probably be aghast at what I did.
On my left side, I had the stud pull once, had a helicoil repair by a shop who knew what they were doing, then had THAT pull out (& I'm not a hamfisted mechanic). I finally drilled the hole out and used a 8 mm SS threaded rod (~80mm long) with a a SS nut that I ground to fit behind the head. Because of the tight fit, the nut does not spin so I don't need to hold it with a wrench.
I didn't have to pull the head but rather slipped the nut in behind/through. There is no leakage to the outside either from the front or the back. You can't see it unless you're looking for it (it's under the spark plug) and I can crank down on the stud more so than with the stock stud (not that I do).
That's actually an excellent fix. And the last time it will ever need attention.
Congrats.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
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