Loss of Compression-Bent valve

[James.A]

Suffered a loss of compression on one cylinder of one of my R75/5's. I pulled the head and saw this.

[James.A]

Then, I held the head up to the light and looked in the exhaust port and found this.

[James.A]

The piston does not show any cracks or damage. Would you run the old piston, or replace it. The bike has 85K miles and around 3000 on a lead free re-build with Black Diamond valves.

[20774]

Hard to tell what the damage is to the piston crown. What does the combustion chamber look like? Did the bike run for any time period with the broken valve? Seems like that would really chew up a piston face and or combustion chamber surface.

[crazydrummerdude]

With only 3k after the rebuild, what do you think caused this?

My R90's got about 30 miles after a lead-free rebuild with Black Diamond valves, too.

[jforgo]

With only 3k after the rebuild, what do you think caused this?

My R90's got about 30 miles after a lead-free rebuild with Black Diamond valves, too.

30 miles? That's it?
Is Black Diamond not the way to go?

[DennisDarrow]

For me, I would have a lot of concern for cracks around the wrist pin (whats the name of that spray on stuff to check for cracked pistons?) and every bearing for all the way down to the crank.
If the piston is just kinda skuffed a bit perhaps I am a bit too concerned; but if the valve notched it pretty good, that force/hammering had to be transfered someplace, like the bearings................Dennis

[crazydrummerdude]

30 miles? That's it?
Is Black Diamond not the way to go?

No no no.. I don't want to start any rumors.

I mean, I just rebuilt my heads, and I was wondering if the same thing might happen to me, given _________. I was wondering if someone could fill in the blank.

[jforgo]

No no no.. I don't want to start any rumors.

I mean, I just rebuilt my heads, and I was wondering if the same thing might happen to me, given _________. I was wondering if someone could fill in the blank.

Oh, OK.
I woudl not expect what we see on pix at 80K with unleaded job

[20774]

I've not heard much good regarding after market valves. BMW valves should be the first consideration if you really want to get the life out of them. This was hashed quite a bit over on the Airheads listserve.

[jforgo]

I've not heard much good regarding after market valves. BMW valves should be the first consideration if you really want to get the life out of them. This was hashed quite a bit over on the Airheads listserve.

Bob's BMW literature claims the Black Diamond is better than BMW factory.

[OHScot]

So was the guide to tight or what do you think happened? Pistons are pretty stout but I would at least pull it, maybe have it magnafluxed or what ever they do to alumium to check for cracks and stuff. Had one that had a noise and I never figured it our till I had it knurled and the crack showed up

[crazydrummerdude]

I've not heard much good regarding after market valves. BMW valves should be the first consideration if you really want to get the life out of them. This was hashed quite a bit over on the Airheads listserve.

Snowbum and the "local" airhead mechanic both use and recommend Black Diamond.. so I went with.

[Bill Burke]

Was it a sudden failure at WFO throttle?

[20774]

Bob's BMW literature claims the Black Diamond is better than BMW factory.

Would they say any different? But I've heard different from other people who also work on Airhead engines.

Edit:

OK, I'll back off of that after reading some of what Ted Porter wrote on the Airheads list back in October 2005. Prior to going into business for himself, he did a lot of his work with Bob's BMW. RE: Bob's BMW literature saying the Black Diamond is better, here's what Ted said in 2005: "In fact the quote they use in their advertising about Black Diamond Valves being superior, came from my mouth to their ad guy." Ted based that upon all of the experimentation he was doing in the mid '80s trying to "fix" the problem with early '80s engine valves cratering.

He goes on to say in that same post:

"The Black Diamond valve is a well made one piece stainless valve that has
been through a hardening process which hardens the keeper slots. It has a
fully machined tulip with a polish swirl finish that may improve flow. It
has a stellite tip, and works well with the Martin and Wells seats
(Kibblewhite now supplies their own seats too). Because of the hardening
process it is black in color and it does not have a steel chrome stem. As a
result it does not wear as well in the guide as a steel chrome stem does.
Sometimes when you take apart a head with Black Diamond valves installed you
will see some guide material imbedded in the stem of the valve. Kibblewhite
says there is a dry film lubricant impregnated into the stem of the valve to
counter this problem, but you can still see evidence of material
transferrence. Opening up the valve to guide clearance seems to help some,
but the issue is still there and now you're running wider clearances than
preferable. I have never had a failure related to this issue, and at the
retail price of about $40.00 for an exhaust valve it is a good deal, but the
material transferrence concerns me and guide wear occurs faster."

So, not too bad, I guess, however it does create a problem that maybe you can work around. If money is your hurdle, them maybe the B.D. valve is a suitable alternative. But when the proper solution is there, albeit not guaranteed, I'd prefer BMW parts. My engine...my wallet...I don't really want to compromise.

[rinty]

I had the valve materials / construction discussion some years ago, with a client of mine who is a professional race / high performance engine builder. At the time, I was having my '82 RS engine completely rebuilt and modded.

My client told me that valve stems and tulips were made of different materials and then hammer welded together; an expensive process. This, to withstand different conditions at different parts of the valve. The cost is not a problem in the automotive scene, where millions are needed, but possibly a problem in an aftermarket where small quantities are made and sold. So the compromise would be to make the valve out of a single alloy, to keep that cost down.

My own tech would only use BMW valves in my motor, after I asked him about putting in aftermarket "high flow" mono alloy stainless steel valves. There was also one report in the News a few years ago, of an engine grenading after stainless steel valves were installed, but these may have been Luftmeister crap.

Just to be clear, I am not commenting on the Black Diamond valves specifically, as I know nothing about them.

[swall]

My comment as a metallurgist--embeded material on the valve stem from the guide is not a good thing. Suggests either the guide to stem clearance was wrong or the choice of materials for guide and stem was not compatible.

[jforgo]

My comment as a metallurgist--embeded material on the valve stem from the guide is not a good thing. Suggests either the guide to stem clearance was wrong or the choice of materials for guide and stem was not compatible.

I do not like this. It seems as though the stainless is "galling", or somehow is lacking in a lubricity property of some sort.

Stainless in other applications seems to be britttle, or not to hold an edge , or to have galling surface-to-surface tendencies, or not withstand torque.

Are automotive valves made from stainless?

[jforgo]

Thanks for the post. Maybe I am missing something, but I am not seeing in it where the BD are judged superior - they seem more of an also-ran, pretty OK for the $ part. Bob's affirmatively says they are better, as well as cheaper. I am not seeibng what is better.

[Oznay]

Mine looks a tad worse than yours. A valve seat let go,and the piston jammed a piece of the seat into the head,makin'it useable as a window prop.I picked up a set of heads from a guy in Calif., am in the process of gettin'it together now.

[The_Veg]

I got alla y'all beat. This happened on the way home from West Bend:

http://vegomatic.smugmug.com/photos/174860436_AuoQG-M.jpg

http://vegomatic.smugmug.com/photos/174860439_MYhit-M.jpg

http://vegomatic.smugmug.com/photos/175796280_Rxv67-M.jpg

http://vegomatic.smugmug.com/photos/175796556_5B7GP-M.jpg

http://vegomatic.smugmug.com/photos/175796162_sSGqv-M.jpg

http://vegomatic.smugmug.com/photos/174860422_ZGWSb-M.jpg

This was with the original BMW valves in a 1995 R100 at 67K miles, gently accelerating through 3rd gear on a 97F day.

[krehmkej]

Well, this is great freakin' news. I have 2.8K on a BD unleaded conversion.

Something else to think about whilst chalking up the miles this year.

I wonder about just swapping in real BMW valves? Just lap them in and go.

I'm tempted? Anyone done this?

[lostboy]

I have used the Kibblewhite "Black Diamond" valves for years and have seen the same problems shown here, as well as what Ted mentions. After much experimentation, I now finish the guide to stem clearance at .003". This seems to eliminate seizures and galling. If you don't have the equipment to accurately measure clearance, replacing valve guides is a real crapshoot. I am not sure that the problem is with the valve; I suspect that Amco 45 is not the best material choice for a valve guide. I continue to experiment.

The veg's problem is seen a bit too often for my tastes-the inertia weld between OEM valve head and stenm has failed. This is not a common failure-after all, jillions of OEM valves are made this way. Virutally all aftermarket valves are one-piece, eliminating at least that problem.

[James.A]

I was on the phone with BE in IN right after I took the head off. We talked it over for at least a half hour. He suggested, and I agreed that since it was the right side cylinder, that I pull the breather to see if a part of the disc might have broken off and been sucked into the combustion chamber. We'll see about that soon enough. When I dis-lodged the keepers, the valve dropped right out, so I don't think the guide was culpable.

When the trouble arose, I was winding down from a VIGOROUS 3 mile run and the bike idled down and quit at a stop light. It re-started and I rode it another 2 miles to home. After that it never started again.

I'm going to take the piston for a good cleaning and Magna Flux. It occurred to me that the under side of the piston might reveal a clue.

I was expecting to find a valve stuck in a guide, A bent push rod, and a broke piston, so it could have been worse, I suppose.

I'm pretty sure I am going to loose the valve set and get the newest incarnation of OEM valves.

[Bill Burke]

My exhaust valve failure right side can be seen here. Note piece of pie missing from the tulip:

http://www.bmwwerkstatt.com/gallery2/main.php?g2_view=core.ShowItem&g2_itemId=1181

The valve failed during a cross country trip after hours of relatively high speed running - in the 5K rpm range on Canada's 403 West of Hamilton. I had Ted Porter replace the valves and springs. His diagnosis: the valve seats had been reground (by a PO, unknown shop) incorrectly - angles on the seats didn't allow enough valve seat cooling contact. This failure caused enough loss of compression that I could only run on the left cylinder. Limped it about 3 KM to a diner and a friend drove his pickup over 150 miles to pick me and the bike up. No sign of the piece of pie from the valve. Our theory is it shot out the exhaust. I did hear a "ping" when the failure occurred. No damage to the piston crown or cylinder wall.

[manicmechanic]

Well, Jim. it was bad enough but could've been worse. However, not defending the BD's, but in some of the newer off-road bikes they seem to be the valves of choice, as the OEM's tend to recede to a knife-edge, particularly the intakes. I'm wondering if perhaps the size of the valves in this case might not be the difference. Here you've got two valves of pretty large diameter, whereas in the off-road application they're four valves about half that size.

Talk to you later.

[AntonLargiader]

Suffered a loss of compression on one cylinder of one of my R75/5's. I pulled the head and saw this.

It's not too clear, but it looks like repeated mild contact rather than sudden severe contact. Did you use the base gasket when you reassembled the top end after the rework?

[barryg]

I use to do head work for a living in another life. I did probably 100 sets of heads of BMW airheads. I used Black Diamond valves on quite a few of them. Never had a problem or come backs due to their failure. Most of my customers seem to get good service out of them. I had the best training and equipment to use. I come from an extensive background in tool&die, machining and maufacturing. I assume that Kibblewhite could possibly have had some defective batches of valves. They produce them by the thousands. I ran very tight tolerences on the clearance between valve and guide. I wanted the customer to get long life out of a set of my reworked heads. My general idea of long life of a set of BMW heads on Airheads is 75 to 100 thousand miles.

[James.A]

It's not too clear, but it looks like repeated mild contact rather than sudden severe contact. Did you use the base gasket when you reassembled the top end after the rework?

Anton, thanks for the note, All I did originally was pull the heads. While the set was loose I put in new push-rod tube seals. I re-used the base gasket that was in place. Repeated mild contact would be consistent with the way the last ride went down.I still think it would be wise to have the piston Magna-Fluxed to remove any doubt.

Thanks to everyone for the comments. JAS

[krehmkej]

Magnaflux testing is only for metals subject to magnetism (iron and steel, most commonly).

The non-destructive tests for for aluminum alloys include X-ray or ultrasonic.

Might be simpler and cheaper to just replace the piston if in doubt.

As always, YMMV.

[James.A]

Magnaflux testing is only for metals subject to magnetism (iron and steel, most commonly).

The non-destructive tests for for aluminum alloys include X-ray or ultrasonic.

Might be simpler and cheaper to just replace the piston if in doubt.

As always, YMMV.
Whatever!... I'm confident that my local "motor parts" jobber can give me a reliable verdict. I don't need to know the science, that's what I pay them for.

[PeoriaMac]

woodnsteel;I'm confident that my local "motor parts" jobber can give me a reliable verdict.

You have a "local motor parts jobber"?????

Mac

[20774]

The non-destructive tests for for aluminum alloys include X-ray or ultrasonic.

Also dye penetrant.

[DennisDarrow]

Kurt, that is what I was refering to earlier but cannot remember what it is called........One coats the piston with a red dye and then spray with white and the cracks appear.......what is this stuff or process called?..........thanks.......Dennis

[20774]

Dennis -

It's a process that I'm somewhat familiar with in the inspections of aircraft...I'm mostly involved with military trainers. The area is treated with a specific fluid that can wick into the discontinuites. The excess liquid is removed and the remaining penetrant returns back to the surface due to capillary action. A developer is used to help contrast the liquid for easier visibility. Sometimes fluorescent light and dye is used to better illuminate the flaw. This works for external flaws only.

Other crack detection methods include eddy current, ultrasonic, mag particle, and x-ray, as previously indicated. Eddy current is good for looking in bores of holes...a current is sent out into the surrounding material and the probe measures irregularities in the current pattern. Ultrasonic bounces waves off surfaces which could include imperfections within the material or on the backside which can't be reached. It can also bounce off the countersunk portion of holes to visual the area without removing the fastener.

There are other fancy ways including something shearography which uses guided light to help see small changes in the surface.

All the methods have advantages and disadvantages and are used in a way to builds on what they're good at.

[James.A]

woodnsteel;I'm confident that my local "motor parts" jobber can give me a reliable verdict.

You have a "local motor parts jobber"?????

Mac
Kalina Machine and Motor Parts in Peoria. They are the successor to Schotthoeffer's Machine shop.

[crazydrummerdude]

Did anyone notice the article in the new Airmail about some guys Black Diamond valves destroying themselves after 8k miles on a rebuild?

:hungover

[ebeeby]

yeah, I noticed that. Bad news.