R65LS Questions

[Red_Hen]

Thanks for the heads-up about the cold and possiblity of breaking plastic - I had all new bulbs in there but I know on the way down to drop off the bike one did break.  I wished they'd checked before buttoning her up but the more important piece is they got the bike running like a swiss watch.

I believe I bought the bulbs at O'Reilly.  Do any of you know the size?  

Also, I looked in my Clymer book and the rubber mounts the mechanic did not install are the two left & right pieces that go under the front of the tank - should I remove the tank and silicone the mounts in place or is there a slot on the frame to install them?

Thanks again!

[Bob_Roller]

I believe the bulb numbers are SAE 158, 168, 193 .

They're an odd bulb without a metal base .

The rubber parts need to have some sort of adhesive on them, no slots on the tank for them .

[Rob Valdez 79 R65]

I believe the consensus for tank pad adhesive was shoe-goo?  Or automobile door weatherstrip adhesive.

[bruce_launceston]

Hi Ken

I don't think there are any pads under the front of the tank other than the cylindrical one in the front centre plus the two that fit on the tank at the rear (these have survived many years cable tied to my frame tubes as opposed to gluing them to the tank).

Cheers Bruce

[Red_Hen]

Thanks Bruce - I think you answered my "next" question about where the pads go.  Sounds like they go in the rear which may mean not having to completely remove the tank.

Zip ties sounds like a good idea but I've got clear silicone and contact cement on hand.  

I did pick up a couple instrument bulbs last night.  The only one I want to get to right now is the left arrow for the turn signal.  Then I hope to ride the bike in the next day or so.

Thanks gang!

[Red_Hen]

Hi Gang,

Got the retainer clips on the seat and did my best to position rubber mounts and lock the tank down onto the frame with on the clip.

Went for a test ride and she was running good.  All of a sudden she got really loud.  When I rolled her into the garage, I noticed the exhaust nut had blown off the bike.  I got in my car, drove down the street and luckily rescued the short part of the Lufmeister 2-in-1 and the exhaust nut.

Don't know if I shared this: when I got the bike the exhaust nuts were frozen on the cylinders. One we got off with the special exhaust nut wrench.  The other started spinning on the exhaust port or hole.  We used a hacksaw to cut off the exhaust nut as it was trashed and corroded.

Now, the bike has been put back together.  I now realize we didn't secure the threaded piece back on the cylinder and the exhaust pressure must be so great that it blew the threaded piece off the exhaust port, taking the exhaust nut and Lufmeister pipe with it - like rocket propulsion.

So, my neighbor helped me get the exhaust nut off.  We'd used anti-seize when putting these back on last fall.  

So my question is now what do I do?  Can the piece be secured on the cylinder w/out disassembling the cylinder or?

I guess I've got a few bugs to work out yet!

[Bob_Roller]

To the best of my knowledge, the threaded part is part of the cylinder head casting, unless a change was made that I haven't heard about .

I've never even heard of this happening before !!!!

[nhmaf]

How the heck did the threaded exhaust port blow off the head?   I've never seen a head crack there, leastwise all the way around the threaded part..

It must have been slightly cracked and perhaps was weakened further when you went after removing the nut with the big wrench, or..... uh-oh...

"I now realize we didn't secure the threaded piece back on the cylinder and the exhaust pressure must be so great that it blew the threaded piece off the exhaust port, taking the exhaust nut and Lufmeister pipe with it - like rocket propulsion."

You didn't remove the exhaust port from the cylinder head when you sawed off the exhaust nut, did you?!?!?

You're either going to need a new head, or, a skilled machine shop with experience in airhead head repairs may be able to weld the threaded exhaust port back onto the head, but it isn't an easy weld repair to do,  IMHO, but I'm a very poor welder at best.

[Red_Hen]

What I meant to say is the threaded piece on the cylinder started turning when we couldn't get the exhaust nut off. That was at the stage when I first got the bike and decided to remove the engine and go through it. In order to remove the engine we needed to remove the exhaust. Maybe the previous owner did some kind of repair - I haven't a clue about the bikes history.

I do know the threaded flange can be tapped onto the exhaust port but I want to figure out the way to permanently attach it so it doesn't happen again. If this means removing the cylinder and sending off for repair than that's what I'll do.  I just want this thing to be a reliable runner and not be 100 or 1000 miles from home and have this happen again  I consider myself lucky it happened right in front of my house!

I'll call Ron tomorrow at Judson - I emailed him the pics - I'm sure there is a solution.  I've waited this long to get it back - now that the bike runs, this is more of a "minor" issue to me.  Just another bump in the road.

[bruce_launceston]

Hi Ken, what you seem to have is someones 'fix' for a stripped thread. Normally the exhaust nut thread is tapped onto the parent metal of the head. It looks as if yours has been stripped and instead of taking the head off and getting the alloy built up and re-threaded they have made the threaded steel? adaptor.
The trick now is how to secure it to the parent metal spigot on the head.
The threaded piece looks to me to be thick enough to drill 2 holes through and countersink them to take a small s.s. screw. The hole will have to be deep enough to allow the exhaust nut to still thread on and the screws could be tapped into holes in the remaining head stub.
It only needs to stop the piece turning and the exhaust nuts do not need to be done up very tight.

I guess it was originally glued on, maybe with JB-Weld or similar. It will need some sort of high temp glue to seal the exhaust gasses in.

[Red_Hen]

Hey Bruce,

Thanks for your suggestion.  On the MOA forum, an airhead suggested I "stake the flange" and use Red loctite to seal it.  Another suggested I take to a machine shop.

Not knowing the history of this bike, it is possible the previous owner may have had trouble removing the exhaust nut when installing the Lufmeister unit.  But I'll never know for sure.

See picture attached - there is a small brass or copper colored small hole on the top of the cylinder where that flange slips on - maybe it was a brass stud that acted like a "Key" to hold it in place.  

I know there is a solution.

[Red_Hen]

I'm not concerned about drilling two small holes through the threaded flange but wondering what the alloy is for the cylinder - will I be drilling through aluminum?

[bruce_launceston]

The cylinder head alloy is quite soft, I guess it's a magnesium alloy. It does look like the previous owner has pinned the threaded sleeve similar to what I suggested with the screws.
I think screws would be easier but you could reinstall a pin. I wouldn't drill right through into the exhaust port in case the pin dropped right through, thats why I thought a threaded fastener would be better.

You could get an engineering workshop to do it but if you are capable and confident do it yourself. I find that if I do it myself I have a better chance of getting what I want.

At leat a pin will stop the sleeve blowing off, if it was a keyway front to back the thread would not turn but there would still be nothing mechanical to stop it sliding forward and off (other than the clamp around the header on the front engine mount, is this missing?).

I think what they did previously was an elegant solution to a common problem and you should be able to get it to work okay.

Cheers Bruce

[Red_Hen]

Thanks, Bruce and all of you.  I've got a plan of attack in place and I'll also share with you in this post some great collective Airhead wisdom I've gathered today.  

Plan 1: attempt to re-attach the flange to the head and properly secure it.  

Plan 2: ride the bike this season, if I have any further problems, pull the head and send to Hanson's BMW in Oregon.  Paul Glaves recommended them as did Ron from Judson Cycle who got my bike running.  I spoke with Ron and he did notice the repair but since he did not initiate the repair, did not think to ask me about it - no fault of his. Aside from this, the heads are in beautiful shape.

Alternate plan: there is a guy in Germany who sells a retro-stainless clamp kit for @ $150 that addresses this issue - apparently, mine is not the first to experience stripped threads.  
http://www.sternmutterersatz.de/BMW-...p-Details.html
Although an option, I like the aesthetics of how a BMW Airhead exhaust should look and don't think I'll be going down this path.

Here's the collective wisdome:

Barry from Arkansas:
 Worked in machineshop and tool&die shops for years. Spent 10 years doing head work on BMW's, Mercedes, Porsche's, Audi's, BMW motorcycles. Fixed a lot of stripped threads on BMW exhaust ports. Set heads up in Milling machine and machined off bad threads. Left most of the exhaust stub material on the head. Made up the new aluminum exhaust threaded sleeves. Looks like the ones in Ken's picture. Mine hade a bout 0.002 to 0.0003 interference fit. Heated the sleeves on a hot plate untill red hot and dropped them on the stubs. Most just bottomed out on the stud. When they cooled down, they were shrunk fit on the stud. My buddy was a welder and would run a a small bead around the stub and sleeve and it was locked on. I would machine or file any excess for a nice look. I made up a set of threaded dies to run over the threaded stubs to make sure the exhaust nuts had a perfect fit. Worked great. Another nice tool is a metric thread tool. You can get them at Sears, probably Northern Tool, others. Their about the length of your hand, 4 sided on both ends. Each end had 4 different metric sizes. I think that tool covered all metric sizes /2's till the end of the airhead run. Handy little tool to fix threads that wean't to bad. I also used my threaded dies to fix a lot of bad threads, and saved alot of my customers from the expense of the more envolved process I just explained.

Paul Glaves: I thought that threaded piece threaded into the head and then the nut went on it.  It now looks like the threaded piece is supposed to slide over the smooth piece in the head and then the nut threads on it.  Is that correct?
If so I have no idea how that is supposed to stay put because as it heats up the threaded collar is going to expand and get loose.  If I understand how they did this then I think brazing is the way to go but I don't know what metal is what.  Is the smooth stub on the front of the head part of the head where they removed the original threads?  If so I don't think even brazing will fix it.
Calls Hansen's BMW in Bedford, Oregon and see if they still fix these things.  The way I have seen them fixed is to build up where the threads used to be and to then machine new threads on the head.

BoxerMAF: Yes it is an alloy and not steel, so one has to be careful if you are putting fine threads into it as they may be easy to strip out.
Most repairs I've seen of exhaust port threads involved welding extra material on stripped-off port threads and re-threading (as the exhaust port threads are easily damaged/galled by stuck on exhaust nuts). I've never seen a fix attempt like this one of apparently staking a threaded collar on. To me, the tricky part of this type of approach is to get the joint to be gas tight and able to handle the temperatures involved. I don't know if it can be done without some form of welding or fitting the head and this steel insert with left-handed threads to screw into the head material somehow.

[bruce_launceston]

Hi Ken, the German stainless steel kits won't work for you as they clamp onto what is left of the threaded stub and yours has been machined off.