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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.
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.
J
James.A
Guest
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.
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.
B
Bill Burke
Guest
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.
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
ABC,AMA(LIFE),MOA,RA,IBMW
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.
Talk to you later.
AntonLargiader
Active member
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?
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.
J
James.A
Guest
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
J
James.A
Guest
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.
Also dye penetrant.
dennisdarrow
#4869 Earned Lifetime mem
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
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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.
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.
J
James.A
Guest
Kalina Machine and Motor Parts in Peoria. They are the successor to Schotthoeffer's Machine shop.
crazydrummerdude
advrider.com
Did anyone notice the article in the new Airmail about some guys Black Diamond valves destroying themselves after 8k miles on a rebuild?
