My experience with Black Diamond valves is limited to Brit bikes with the soft (pre-1975) valve seats. The bike in question was used for cross country riding and had very high mileage (for a Brit). There was zero damage to the BD valves. Except for some soot, they looked like they were right out of the package. However, they were so hard that they accelerated the wear on the seats to an unbelievable degree. It was one of the few Brit bikes (out of several thousand) I've worked on, that HAD to have new seats installed.

You definitely have to match the hardness of the seat to the valve. You can't have an extreme spread, as in the case above. How you achieve that balance I can't say.

The problem I have with Bob Fleischer's (Snowbum) brilliant writings is it's sometimes hard to tell when he wrote it. The hardness of valves and valve seats is something that changed a lot over 15 years. Was his article written in the beginning, middle, or end of that era ? Because the technology of valves and valve seats was changing wildly during that time.

The snowbum article I found is on this site and was last updated this year.
I understand completely about the hardness issues. Same experience with older leaded heads.
It appears the 1981 seats are too hard and probably don't conduct heat well resulting in valve and guide wear. As far as I can measure all the wear is on the valves. The installed EX valve seats look fine and measure fine.

I would love to find a source hardness of the original 1981 BMW valves to compare to these Kibblewhite. I'm very tempted to just throw the Kibblewhite in and reassemble. Even if they are only as hard, I'll be well over another 100k miles even with new head gaskets to just break even cost point(own labor naturally).

Thanks

I can't argue with that reasoning based on price.

Maybe an email to Snowbum asking for some clarification is in order. You can't argue with the cost of an email !

All the best.

I had a bad experience using Black Diamond valves along with BMW guides in a head re-build a few years ago. This was on my R75/5. I let the parts guy from a major dealership talk me in to saving a few hundred dollars on parts. That savings turned in to an additional $600 when one of the BD valves stuck in a new BMW guide and a piston hit it. The valve bent but the piston did not fracture, so I guess I got lucky. I had to have the heads re-worked a second time using the current OEM valves from BMW. The original issue was with the exhaust valve seats which were extremely eroded. All new everything the first time around. BMW valves the second time. I have thousands of miles without trouble after the second operation.

Interesting story.
Question, how many miles did you have before the stuck valve? Because if it happened first ride where the bike got up to normal operating temp I'd seriously suspect the machinist did not properly hone the guide for clearance. Did you get from Kibblewhite their recommended clearance for a BD in stock guide?
Do you know what the stem to guide clearance was set to? My book says 0.0020inch for stock stem to stock guide. I'll post if I get a different number for the BD.
Thanks
Edward

The motor had around 600 miles. As far as the specs, I can't say. The machine shop that did the work used the specs from the OEM manual. I think it might have been O.K. if we had left the old guides in the heads. Apparently, the expansion rate of the stainless steel valves was more than the guides could tolerate.

It does sound like incompatible expansion rates.

After much study and talking to several machinists I'm feeling most comfortable with MaxBMX in NH. So today I dropped the heads off at MaxBMW to the machine work. I was quite pleased to see several Airheads from an R26 to some sweet frankenbike dirt /6. As well as several airhead heads in the machine shop. Their machinist Nathan has been in the airhead work for many decades.
My final choice was to used new BMW Valve Seats, with Kibblewhite valves and guides.

The service manager, Joe, said my heads will get front line service and my hope is to get them finished by mid next week as I'm signed up for the Team Strange New England Rally on the 16th and then IBA SS1000 on the Fall Equinox. I'd really like to put a couple hundred on the "new" heads before that rally. It's a bit of a drive from my home, but worth it to view the facilities and talk with the guys running the place. So far happy.

Update: The old girl now has about 1500miles on the new exhaust valves with about 1k at highway 4-5k rpm. After the initial 350miles(on the Team Lyle Rally, oldest bike and 2nd place rookie) of break-in the valve were reset. Now after an additional 1200miles the valves were checked and all still in spec! My only issue was a ham fisted PO who over torqued the right valve cover so even with very gentle treatment that center stud finally went for a walkabout. 🙁 Have a helicoil kit on order but probably will not have it fixed before we head south for a sunnier winter. I am taking the bike south with us and have another Winter Solstice SS1000 and a Feb CC50 planned.

I reused the original seats(recut) with Kibblewhite BD valves and stems. New springs, collets, gaskets. First re-torque and clearances set at about 90miles and the first heat cycle, then at 350miles and 3rd heat cycle. And lastly at 1500miles and all torques and clearances fine on heat cycle 4. The head gaskets seem to have settled in to it's new home for the duration.
Yes the OEM valves were "tuliping" it was quite obvious the majority of the wear was in the valves and stems.

I'm glad this topic came up again. Cruising through YouTube the other night and came across this Ted Porter video. Wait for him to explain the second issue...

Hope this helps.

"The bitterness of poor quality remains long after the sweetness of low price is forgotten."

LOL, Not an Argument! 🙂 But seriously nothing was bought was from China aka Cheap Chinese Cra*. Although generally the quality has improved greatly in the last 30 years 🙂
Are you suggesting American made valves/guides are inferior to German? I suppose Time will tell....

🙂 I was just echoing what Ted had to say in his video, another way. May not apply directly to your situation.