Seized Exhaust Header Nut

[montmil]

To replace my R65's timing chain required removing the exhaust headers. This permits the timing case cover to come off rather than be blocked by the forward exhaust x-over tube.

Left side exhaust nut, no problem. Right side, a whole other story.

With the appropriate header nut wrench -I think it looks like a prehistoric war club- the left side nut would only turn a very small amount. No amount of PB Blaster or heat applications helped.

I had a funky close-quarter holder for a hacksaw blade, so mounted up an 18 TPI blade and got after the aluminum exhaust nut.

Several wraps of tape protected the vintage patina of the exhaust pipe. I worked the blade into the header nut at the cylinder end. Not a lot of working space up forward due to exhaust pipe interference. Saw, saw ,saw...

When the cut looked as if is was close to the threaded exhaust stub, I was checking my work frequently. As the saw blade made its initial contact with the steel threads, the sound of the work changed dramatically.

Look closely at the cut area in the photo. The "dots" are actually the exposed steel threads. Stop sawing!

A think chisel and a couple moderate taps with a ball-peen hammer spread the nut enough that the wrench was able to remove the nut. Additional squirts of PB Blaster helped.




After moving the exhaust system slightly forward, there was enough clearance to fully unscrew the exhaust nuts without binding on the sharp curvature of the header pipes.

Next chore will be to repair as best as I can the damaged threads I discovered. Small files and a lot of patience will help partially restore the threads that appear to be either melted (?) or having some weld added. Weird. At least the boogered up threads are in the middle of the exhaust stub. Appears to be enough good threads at the front and back of the stub to secure the exhaust nut

Danged if one thing doesn't lead to another. .

[Bob_Roller]

When I removed my exhaust nuts the first time, doing a timing chain replacement, I had a 25 pound dead blow hammer, and with one mighty hit, the nuts came right off, along with all of the threads  on the exhaust spigot.

Wasn't a total bust, when I removed the heads to have the threads repaired , I found that the valves on both cylinders were so worn, that I had at best 5,000 miles before they would have 'collapsed' into the exhaust port ( valve face plastic deformation).

[Justin B.]

Monte, there are no steel threads - everything's aluminum, hence all of the problems.  The "melted" threads were probably just "galled" by the nut.  The same thing happened to a slight degree on our R65RS.  The nut came loose, turned freely about 1/4 turn, tightened up, I tried another tug and I think that's where the damage came in.  On the other side I stopped immediately after it tightened, cut off the nut, and all was perfect.  I cleaned up the damaged threads with a three-square swiss file and when I got it real close I painted valve lapping compound on the threads and lapped them in with the new exhaust nut.

[montmil]

Monte, there are no steel threads - everything's aluminum, hence all of the problems... I cleaned up the damaged threads with a three-square swiss file and when I got it real close I painted valve lapping compound on the threads and lapped them in with the new exhaust nut.

That's good info. Already have the files out and a fresh tube of Permatex valve compound along with their anti-seize goop. Just frustrating at times. Typical with old bikes, cars, parents...

Friday evening and Saturday morning will be Beemer-Dedicated time. Saturday afternoon and evening, I'm flying solo with two of my grandchildren. Little girls ages 3 & 7. Where did I leave that Valium sample...?

Monte

[Justin B.]

Chisel works fine, don't worry about nicking the threads with the saw they'll still work just fine.  I used a Sawzall to cut mine off and put a pretty good groove in 'em with no ill effect...

[Ed Miller]

I'm glad I'm not the only one who used a power tool.  

I keep forgetting to buy valve grinding compound.  I used to have a bit of it, even though I never grind valves, but I can't find it.  Using that on the threads to clean them up better sounds like a great idea.  There's something else I wanted the grinding compound for but I can't remember right now what it was.

[nhmaf]

One of the heads on my R65 has some compromised threads - I recently tried to clean them up with an actual thread file.   It helped, but it was taking more material out than I anticipated.  The new exhaust nut still wouldn't go on - I think valve grinding compound would have helped here too.   But I was worried that the threads were down low enough that cutting them to fit the new nut would leave very little to grip.  The old nut still goes on/off well and grips tight as its threads are now a custom fit to the head, so I just take them off every year, clean em good and reapply more anti-seize.   When I eventually end up sending the heads out for new valve seats I'll have them repair the threads on that head as well.

The joys of old bikes !
 :-?

[Justin B.]

I spent probably 2 hours with a fine Swiss file before I was able to get the nut started far enough to start the lapping process.

[MrRiden]

Looks like a textbook case! One thing in the photo gets me tho. It looks to me like the paint on the hacksaw blade is worn off on the back side of the blade while the side with teeth looks pristine. The toothed side cuts faster [nyuk nyuk nyuk] or is that a double edged blade?
rich
who has been known to butter his bread on the bottom.

[montmil]

I feel much better, now.

The galled exhaust nut is off, a couple hours with triangular files of various sizes and some lapping in with valve grinding compound got the new nut on pretty well. The exhaust stub has some damage but will hold.



Working the header pipes out of the exhaust ports -both sides- required holding my tongue just right plus a few gentle love taps from a dead blow hammer. With the multiple exhaust pipe clamps, I believe the reworked threads will pass muster and grip firmly.

No way those X-over pipes were letting go so removed the pipe system as one unit. Someday I'll have a completely new exhaust system... might not be on this bike!

Props to Re-Psycle BMW up Ohio way. http://re-psycle.com/ Called Marco approx 1045 hours Tuesday morning and the header nut was delivered before 1000 hours Thursday. Actually less than 48 hours and at regular USPS rate. I know when the part arrived as I was goofing off work playing with motorcycles!

With the exhaust system off, working space allowed me to add a shim washer into the sidestand mount. The OEM "spacer" in the bracket is more like a heim joint ball but my AN hardware stores came thru with a thin, wide-area washer. Firmer. Less slop. No rattles. Washer doesn't show in pic.



Tomorrow, Saturday, we'll get into the timing chain case...

Monte

[Justin B.]

Take lots of pics and write up an article on it for the Wiki...

[montmil]

Looks like a textbook case! One thing in the photo gets me tho. It looks to me like the paint on the hacksaw blade is worn off on the back side of the blade while the side with teeth looks pristine. The toothed side cuts faster [nyuk nyuk nyuk] or is that a double edged blade?
rich
who has been known to butter his bread on the bottom.

If I understand your observation correctly, Rich, what you're seeing is a clamping device that holds a hacksaw blade at only one end. Much of the blade is inside the handle. The blade is not under tension as the unsecured end extends out only about an inch from the "worn off paint". Helpful for cutting in close quarters.

Also, the usual blade install position is with the teeth positioned to cut on the pull stroke. Prevents blade buckling. As I was working with aluminum and in a sorta snug position, I had the teeth set to cut on the push stroke.

Monte

[nhmaf]

Monte - I know what you mean about those crossover pipes - I tried to get at least one side of the front crossover loose to facilitate header pipe removal and refit, and despite many copius applications of PB Blaster and attempts at being patient, I ended up snapping off one of the extraordinarily corroded cinch bolt fittings on one end of the crossover - ARGH !   The pipe is still on the pretty tight but just to be sure I'll now have to hunt for something that looks a bit better than an old hose-clamp - the headers are still solid, but the entire surface of these things rusts rapidly - gotta plan to scrub it all down again and repaint it this year, I think.   Even though it won't be stock anymore - I'm thinking of pulling out my MAC 2-1 exhaust system for it - provided it will clear my saddlebag.

[montmil]

Mike, I found two of the four cinch bolt fittings on my x-over pipes to be rotted away! Rusted tight as they are, I'm not even going to worry with hose clamps.

Eventually, rather than trash the remaining semi-good clamps, I just dropped the entire exhaust assembly down onto the floor. Rotate the pipe assembly 90-degrees about the center stand, rock the scooter up on one leg, kick exhaust, rock onto other leg and kick exhaust pipes across shop floor. Really, really classy.  

Taking a break right now from the timing chain chore. Need an R65.org fix. About to fire up the propane torch to heat the case in the bearing area and pop off the timing chain case. Cautiously optimistic...

Later,  Monte

[Justin B.]

Have you tried with a bit of "rapping" before putting the torch to it?  I have done two chains (r65 and r100) and neither one required any heat.