Partially stripped hole for "special nut" rod...

[szurszewski]

OK - so that's an, uh, awkward title, but it's basically where I'm at. In removing the valve covers from my R60/7, the "special nut" on the left seemed a bit stuck at first and then began turning way too easily. Upon inspection the deepest threads are stripped, so it will go in just fine at first, and then it spins endlessly (obviously not doing much good helping hold the cover on at that point).

I'm thinking a thread repair is the way to go, but I've never done one. I've read about various repairs, so I'm up on the basics, but I'm wondering if anyone has ever done this particular repair... Also, any thoughts on Time-sert (sp?) vs Helicoil would be appreciated if you have them.

Barring any better ideas or warnings of dire consequences, I figure I'll take the threaded rod/stud piece into the semi-local semi-warehouse fastener emporium (Tacoma Screw Products) and see if they have a repair kit to match up with it.

 

[crazydrummerdude]

I'm not much help, but...

I've got a stripped one on my R90/6.

One of these days (or years), I'll go to an Airhead tech day and see if I can convince some guys to help me with it.

You should try that.. and report back.

 

[kgadley01]

I don't know if helicoils are available in metric, though they probley are. before I would use a helicoil, I would run a bottom Tap in and out a couple times. You can get a cheap set of metric taps at most Harbor Freight stores. if that seems to give you some grip, I would reinstall with some BLUE loctite. good luck...

 

[skiteach]

Used Helicoils for years-they do come in metric. They are fairly easy to install, reliable and readably available. Haven't used many of the other types of thread repair.

 

[AnnapolisAirhead]

I have one stripped center stud on a valve cover. Looks like it was helicoiled before (I've heard some heads actually came from the factory that way??). I just keep an eye on it, its fairly tight but I need to fix it. I think its stripped on the head where the stud threads in...ugh.

Unintentional thread hijack...but a similar problem.

 

[Jeff488]

I had the same problem. Got a piece of metric all-thread rod and appropriately sized nuts.
Cut the rod to a length which allowed the nut(patiently ground down to fit in the hole below the spark plug), threaded the rod through the nut and installed the cover using the cap nut. One of these days I'll loctite the nut, when I think to buy a tube when at the local parts store.
With this mod one need not worry much about over torqueing the cap nut.
May be a bit "shade tree", but it works.
One of these days when I forget on which side I did the mod and strip out the other stud, I'll do the same with it. BTW the PO stripped the first one, which is just one item on a list of things he forgot to tell me. May he catch a permanent rash in his nether regions.

 

[James.A]

Last year, I bought a helicoil set for this size at my local Napa store. However, I had to chase down the correct sized drill bit for enlarging the hole at an Ace hardware 10 miles away in the next town down the road.

After ignoring the problem for many years, I looked down there one day to discover that the nut and stud had fallen out.

Finding an experienced helper is good advice. If you do the repair with the head on the motor, stuff rags in the holes where the push rods emerge to prevent metal shavings from getting in the motor.

 

[TGHSMITH]

for the center stud it is much better to use something like a timesert, there is enough material around the hole to put in something beefier than a heilcoil, this can be done with the head on the bike just cover the exposed engine areas very well, call around to machine shops that work on metric stuff. this is common work for them, if you pull the valve covers it will take less than 10 minutes a side(do both sides and save a second trip) I had one bike done in the parking lot.

 

[roncooper]

I once used epoxy to hold the center stud in a 60/6. It lasted for years- was in there when I sold the bike.

 

[plaka]

Timeserts are superior

They are a solit threaded shell as opposed to the helicoils metal coil. One advantage of this is that the solid shell can be installed with green studlocker. It is now very permanent. Tough to play this game with a Helicoil as the studlocker bleeds through the coil. In this particular application you are going to be putting in that stud with studlocker anyway so it could be a toss up.

Whichever you go with buy a kit. It will have several coils or inserts, the drill, the tap and the install tool. Graingers is one source. Split the price with others. Maybe around the local club.

I resolved this on my /5 heads by removing the stud from the other side andd never using the center nuts again. They are not needed and my rocker covers didn't leak (weep a bit, yes, but I got cheap on replacing the gaskets...) . As I understand it the original plan was to use that center nut to hold on the rocker covers. It didn't work, they leaked. So the two little 10mm nuts/studs were added at the rim. This worked---but made the center nut obsolete.

 

[jforgo]

Maybe I am confused here, but it seems there are separate, distinct issues being discussed here.
If the NUT is stripped, then why not get a new nut, chase threads on stud with a die?
If the protruding STUD is stripped, why not replace it? these are available from BMW.
If the HOLE in the head where the stud goes is stripped, only then are we talking helicoil/tiimesert.
It seems the last situation here is the worst - but can be prevented by addressing the easier stuff as it arises.

 

[Polarbear]

Its an OLD R problem;

Many many have had this failure, so don't feel too bad. R100/7 here and I have done a better fix than many! I Removed the entire stud from the head and have tapped new threads to recieve a BOLT, for my assembly. Works so much better than the original nut on stud thing. Any hardware store will have the bolt, which you must measure correctly of course for length, but its a better solution to an age old issue on R's. You can use an allen head or hex head bolt, as you wish. The threads are bigger in the head and not likely to fail now. I know your nut was the issue, but you will have the stud go south sooner or later. Its too small. My thoughts, Randy

 

[bearsfolks]

Special bolt stripped

The center bolts on both valve covers have stripped over the years. I found the easiest and best repair is to buy a metric threaded rod and cut a new stud that's about 1 cm longer than the original. Then clean out the hole in the head with brake cleaner. I used JB Weld on the threads of the rod and screwed it all the way into the head. After hardening it has worked fine for over 6 years and counting. The first side was repaired with a heli-coil by a shop. It has worked fine for about 10 years so far. They charged $50.

JB Weld and a slightly longer stud is the way to go.

 

[szurszewski]

Maybe I am confused here, but it seems there are separate, distinct issues being discussed here.
If the NUT is stripped, then why not get a new nut, chase threads on stud with a die?
If the protruding STUD is stripped, why not replace it? these are available from BMW.
If the HOLE in the head where the stud goes is stripped, only then are we talking helicoil/tiimesert.
It seems the last situation here is the worst - but can be prevented by addressing the easier stuff as it arises.

Actually, mine is the last situation (hole in the head is stripped); after reading your reply I went back and re-read my post ... I was pretty unclear and am now surprised that most people seem to have come to the right conclusion when I pretty much said the wrong thing. (I'm going to blame a very recent schedule change at work for my lack of clarity.)

Thanks to all for the advice, thoughts and suggestions - I haven't decided what to do yet but it will be a few days before I have time to do anything anyway. I'm leaning towards a timesert or helicoil (which will depend on what's locally/easily available and at what cost) because the bike is due to go up for sale and that seems like the closest to stock/original I could do. If I were going to keep it, I think I'd go for a slightly oversized threaded stud with nuts on BOTH ends, or tapping the head for a larger allen bolt as those fixes seem like they address the problem more than just the symptom...actually, I might just do bolts anyway on both sides if I can find an appropriate quality bolt.

Randy/Polarbear: have you had any issues with the bolt(s) loosening from vibration or anything? Do you use any type of washer between the bolt head and the valve cover?

 

[szurszewski]

Update - Repair Complete

Thanks again to all who contributed thoughts/suggestions and general experience.

I finally had time to get something done about this (actually, I had time last weekend - but not until Saturday and I wasn't able to find a place carrying the hardware that was open on weekends). I ended up going up from the M8 threaded rod/special nut to a simple stainless hex/allen socket head M10 screw and wave/spring washer.

If you're thinking of doing this yourself, here is what I did:
removed the old hardware (only necessary on one side, as the other had fallen out )
carefully sealed off the exposed engine bits to avoid metal pieces getting in there (I "recycled" some shopping bags and secured with rubber bands)
drilled out what was left of the threads with an oiled bit (first 5/16 and 11/32)
tapped with an M10 1.50 pitch tap
enlarged valve cover hole just enough to accept new hardware
carefully checked for any metal shards/flakes and cleaned as required
reassembled

Even having never tapped anything before this project (I did practice on some scraps before I went at the heads) it was not a big deal. The only problem I encountered was that on the side that hadn't fallen apart, someone had already done a thread repair (helicoil, I think). I didn't notice this at first as the valve cover gasket also covered up the evidence; I did notice when I tried to drill the hole - hard to drill at first, and then the insert broke loose - wasn't too friendly to the drill bit. I was lucky that the hole for the insert was just about exactly the right size to tap for the M10 1.50 threads.

The fasteners are from a place called Tacoma Screw Products (part number: 214-511-1); M10x65mm - ended up being just about the perfect length (they are almost flush but slightly proud of the backside of the hole in the head) but you could probably get away with up to a 70mm. Total cost for the job (including $15 for a cheap but serviceable tap/die set from Harbor Freight) was $19.31 plus about an hour of time.

I don't know what the proper torque would be for these now, but since the bike went a week without anything on one side (no leaks), I'm thinking they aren't super-critical anyway, and I just hand tightened them and stopped well before I felt likely to strip out my new threads.

I didn't get any pics as my wife had the digicam at school, but I am attaching a pic of the type of screw I used. It looks great and most non-airhead people would probably take it for stock as the head matches other fasteners on the bike (like the footpeg mounts); also, the socket is 8mm, so the stock kit has an allen wrench in that will work with these.