New Valve Seat Metallurgy for 1978

I ran across this information in the Feb 1985 ON from the Tech Editor, Dave Parker. The subject was about using unleaded fuel and that replacing valve seats, especially the exhaust seat, was the way to convert over to run unleaded fuel. He cited that San Jose would do the job turnkey for $351 plus the cost of shipping the heads...only the seats were replaced and existing valves matched to the new seats. Ah, those were the days!!

He goes on to state that while there was no cutoff for all models, he had information that said all R100/7 models with VINs higher than "614741 (1978)" already had the new metallurgy. I'm assuming he means the metallurgy that showed up in the 1981 models, the same metallurgy that didn't transfer heat very well into the heads. Those seats were later replaced in the 1985 models.

Six digits isn't a valid serial number, but in looking at the spread of US numbers, the first VIN for Dec 1977 was 6147121 and the first for Jan 1978 was 6147574. Assuming Dave dropped the last digit, that would mean that mid to late December 1977 bikes were fitted with the new seats.

In another tech article in April 1989, Dave indicated that BMW AG had switched to "Bleifrei" valve seats in all US motorcycles in 1979. The seats could be identified by a very small groove on the inside, below the seat. The specified seat contact was a width of 2mm and along with a 30 degree contact angle; this would provide better heat transfer.

Nice tech history tidbit, Thanks Kurt!

20774 said:

He goes on to state that while there was no cutoff for all models, he had information that said all R100/7 models with VINs higher than "614741 (1978)" already had the new metallurgy. I'm assuming he means the metallurgy that showed up in the 1981 models, the same metallurgy that didn't transfer heat very well into the heads. Those seats were later replaced in the 1985 models.

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Are you suggesting that the "new Metallurgy" seats that he is referring to, that was initially put into the R100s with a newer number than 614741x was LATER replaced with another metallurgy in the later 1985 models? If so, shouldn't we want the newest metallurgy that started in the 1985 models?

I just have been thinking of having my heads done this winter (not sure what all I would get done), so I want to be sure while I am having it done to use the right stuff.

Thanks,
jlc

BMW currently supplies valve seats made of the "correct" alloy. I did this work on one of my 750's 4 years ago.

Jimmy -

I wish I knew exactly what Dave Parker meant when he wrote that. It's a bit confusing when he referred to "new" metallurgy. It is my understanding that there has only been three basic version of valves for Airheads. The ones from 1985-on (which is what you get when you order OEM parts now), the ones from 1981-1984 where the seats didn't transfer heat well, causing valve face problems, and everything else. I guess I read that there might have been a transition period from 1978 to 1980 where the '81-84 metallurgy was being introduced. Generally, the problem with the valves/seats is heat...d'oh! The issues have always been worse on the 1000cc bikes, and worse still on bikes that run fairings (aftermarket or RT/RS). I'm sure it has to do with how the owner runs the bike, too, which will generate more/less heat.

As I posted in my top end overhaul earlier this year, I had my heads refurbed by Ted Porter. Tom Cutter does heads. Oak used to do heads...maybe still does. There are other machine shops that could do heads as discussed in a related thread right now. If you know what you're doing and know what you want, sourcing the stuff yourself might be a way to go. I opted for more experience than I had for my heads. My heads are "zero-timed"...everything is back to the newest and best in terms of valves, seats, and guides...oh, and my valve springs were "tired" so they were replaced. Actually, my intake seats are original per my work statement...they don't see nearly the issues that the exhaust seats do.

I don't think I know enough to "source" anything. That's why I have been asking so many questions - just to become "knowledgeable" enough just to know what questions to ask when I decide to see where I will send the heads to get the work done. I don't want to get the wrong things done, nor do I want purchase any more than I need.

I just want to do "general purpose" enjoyment riding that is pretty much trouble free - no "hot shot" riding, or "sport" riding. I won't need the latest in anything for speed or acceleration, just want to be reliable and trouble free for the next few years - let the next owner worry about more - after I "kick the bucket."

The two main things I want done, is check the valves for wear, and the guides, too. Replace either if needed, and then regrind/re-seat to last about 100,000 miles. My bike right now only has 48,000 miles so it may not need anything done, but I need an expert (NOT me), who knows BMWs to check them out. I would have to trust him, as I know nothing about this technical of work. I could, while down, get upgrades (harder or better seats?) if reasonable price as I can't afford much more $$$ if you know what I mean.

jimmylee said:

as I can't afford much more $$$ if you know what I mean.

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Understand...everyone has their own drivers and restrictions. I'd let your rebuilder first assess heads (they should do that as a matter of course) and give you options from a cost and reliability standpoint. As a minimum, and with very little experience, I would think exhaust seats and guides, maybe guides on the intake side, might be all that's needed, with regrind/relap of the intake seats. With so few miles, you're probably in good shape. My recent overhaul was 50/50 parts/labor. And probably for very little more labor, the whole head can be renewed. General costs are:

- valves $50-75 each (exhaust are more expensive)
- seats about $20 each
- guides about 10 each

The other thing you could do is project how many more miles you think you'll put on the bike and then work towards that. Still no guarantee things won't go south in short order. But for every dollar spent, that pucker factor gets smaller.

Interesting info on the valve seats Kurt. I've read conflicting info on the issue of unleaded fuel and BMW heads. I worry a bit about both my airheads in this regard. I have an '81 G/S with (supposedly) around 30K miles and a '82 RS with just over 60K miles on it. The G/S is from Salzburg so it is a EU model and the RS is a Canuck bike. I am fairly certain both have the original heads and have not been rebuilt yet.

Am I correct in assuming:
- neither would have the new post '85 valve seats (no way to tell without disassembly)
- both should be OK for unleaded fuel

My understanding is I should be keeping an eye on the tappet adjustments as this is the best way to detect early valve recession. I should probably also be doing annual warm engine open carb compression tests to monitor condition.

Both bikes run pretty well but advice is always welcome.

Bikes from the early 80's are subject to a phenomenon called "valve plastic deformation". This is where the valve faces get soft and de-form from insufficient heat transfer, on exhaust valves particularly.

Valve seat recession occurs on earlier (70's) exhaust seats where the seat runs hot and erodes over many miles.

In 70's motors, the absence on T.E.L. (lead) in gasoline contributes to the phenomenon because the lead lubricates the contact surface where the exhaust valve contacts the seat.

In pre-1985 motors, the 1st generation hardened exhaust seats allow the exhaust valves to run hot and deform over many thousands of miles.

In either case, you might find yourself adjusting you valve clearance very often.

Valve plastic deformation will ultimately result in compression loss.

Valve seat erosion ultimately results in catastrophic failure where the valve seat "let's go" and rattles around in the combustion chamber.

+1 What James said! Oak did call the '81-84 issue VFPD which was the term for valve face plastic deformation.

20774 said:

+1 What James said! Oak did call the '81-84 issue VFPD which was the term for valve face plastic deformation.

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Kurt, thank you for sharing the info in your original post. You have provided an opportunity for a discussion of this issue that many of our current forum members might not be aware of.

Well done.

James.A said:

Bikes from the early 80's are subject to a phenomenon called "valve plastic deformation". This is where the valve faces get soft and de-form from insufficient heat transfer, on exhaust valves particularly.

Valve seat recession occurs on earlier (70's) exhaust seats where the seat runs hot and erodes over many miles.

In 70's motors, the absence on T.E.L. (lead) in gasoline contributes to the phenomenon because the lead lubricates the contact surface where the exhaust valve contacts the seat.

In pre-1985 motors, the 1st generation hardened exhaust seats allow the exhaust valves to run hot and deform over many thousands of miles.

In either case, you might find yourself adjusting you valve clearance very often.

Valve plastic deformation will ultimately result in compression loss.

Valve seat erosion ultimately results in catastrophic failure where the valve seat "let's go" and rattles around in the combustion chamber.

Click to expand...

Won't both of these situations evidence themselves in constantly having to re-adjust valve clearances often? If so, how often and how much gap changing in that period of time (or miles)?

jimmylee said:

Won't both of these situations evidence themselves in constantly having to re-adjust valve clearances often? If so, how often and how much gap changing in that period of time (or miles)?

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Yes...either valve recession or VFPD have the same symptom of clearances closing quickly. What I've heard is if you have to reset clearances every 1000 miles, it's probably time to limit riding and begin thinking about an overhaul. Off the top of my head, if you lost around half the clearance in that time, that would be something to monitor very closely. Any more often than that would be cause for concern.

jimmylee said:

Won't both of these situations evidence themselves in constantly having to re-adjust valve clearances often? If so, how often and how much gap changing in that period of time (or miles)?

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The short answer is YES.

On my 1973 R75/5, I was having to adjust the valve tappets about every 500miles before I pulled the heads to look at what was going on. In that case, rolling off throttle would allow the motor to idle down and quit running. It revealed itself when I would throttle down coming up an exit ramp and when I pulled the clutch to stop, the motor would quit. A valve adjustment would restore a stable idle. On the side of the road, with a hot motor, the exhaust tappet clearance would be zero. I lived with that situation for a few years.

Given what I have seen in pictures of VFPD, you would experience compression loss at the point of failure. With VFPD the edges of the exhaust valve erode until they are like sharpened knife edges, then they wear away to where they look like tulip flowers That is where you would have compression loss.

With valve seat erosion, the edge of the valve appears to be sunk in to the seat. Eventually the seat looses it's affinity to its fitment in the head casting and comes loose.

Bottom line, if you are adjusting your valve rockers frequently, you have an issue.

20774 said:

In another tech article in April 1989, Dave indicated that BMW AG had switched to "Bleifrei" valve seats in all US motorcycles in 1979. The seats could be identified by a very small groove on the inside, below the seat. The specified seat contact was a width of 2mm and along with a 30 degree contact angle; this would provide better heat transfer.

Click to expand...

Just to clarify this: the 30 degree faces happened around '88 (shortly before he wrote that) when the R100 engine was re-introduced, not back in '79. AFAIK the exhaust seat was always 2mm. The single-groove seats are the bad ones; the '85-on seats have two grooves.

20774 said:

Yes...either valve recession or VFPD have the same symptom of clearances closing quickly. What I've heard is if you have to reset clearances every 1000 miles, it's probably time to limit riding and begin thinking about an overhaul. Off the top of my head, if you lost around half the clearance in that time, that would be something to monitor very closely. Any more often than that would be cause for concern.

Click to expand...

Thankfully I don't have that constant valve setting issue as I have literally gone several thousands of miles since last setting and there was no noticeable difference, maybe a thousandth or two. No mushrooming of valve stem, and it appears like I have a lot of adjustment left on the valve rockers screws/nuts.

I am aware of the stalling issue as I had it on my /2 until I learned to increase valve clearances - then it ran fine.

Some months ago in the ON Matt Parkhouse provided some useful information on this subject. The part that got my attention were photos of the valve adjuster showing few threads left for increasing the gap during the adjustment process. Seems like a simple way to judge what's going on with the exhaust valves. I've also heard a figure of approximately 80,000 miles give or take as a rule of thumb for when the heads usually need to be done. I'm not sure if this is applicable to the next 80,000 or not. Better parts may increase the longevity.

A read of Matt's article will probably be helpful. Oak published an article a few years ago in the Airhead Club magazine that struck me as the end all on the subject of Airhead valve problems. A back issue might be available if you are interested.

Dave Parker worked for a company that made an additive called Duralt if memory serves that was supposed to protect valve heads/seats. I once wrote to Editor Don Douglass that if Dave tried to use his Owners News column to sell that stuff one more time I was going to puke into the magazine. I didn't read much more about this additive.

BMW made TWO major exhaust seat changes in those years. The original problem was that absent lead the seats would wear and clearances would close. So in '80 or so they went to a new hard seat material. Exhaust valve clearances continued to close at very short intervals. Engines were torn down and distorted exhaust valves were found. The valve heads "tuliped" and were pulled further through the seats. The seats looked perfect. Many dealers replaced the exhaust valves thought to be defective. And many owners soon returned with complaints of rapidly closing exhaust valve clearances again. The cure was worse than the disease.

After a few years BMW figured out the problem was not with the valves; the problem was that the new hard seat material was very poor at conducting heat away from the heads of the valves. The valve heads were inadequately cooled, overheated, and deformed. Circa 1985 BMW went to the SECOND generation of lead-free hardened seats. This cured the valve head cooling issue and the closing of valve clearances in very short mileages seemed to generally disappear.

Oak wrote extensively on this problem in the time period that it was happening. Some of us continue to think that Oak actually figured out the problem and told BMW!

BMW also changed from 45-degree to 30-degree valve angles to get more contact area.

PGlaves said:

BMW made TWO major exhaust seat changes in those years. The original problem was that absent lead the seats would wear and clearances would close. So in '80 or so they went to a new hard seat material. Exhaust valve clearances continued to close at very short intervals. Engines were torn down and distorted exhaust valves were found. The valve heads "tuliped" and were pulled further through the seats. The seats looked perfect. Many dealers replaced the exhaust valves thought to be defective. And many owners soon returned with complaints of rapidly closing exhaust valve clearances again. The cure was worse than the disease.

After a few years BMW figured out the problem was not with the valves; the problem was that the new hard seat material was very poor at conducting heat away from the heads of the valves. The valve heads were inadequately cooled, overheated, and deformed. Circa 1985 BMW went to the SECOND generation of lead-free hardened seats. This cured the valve head cooling issue and the closing of valve clearances in very short mileages seemed to generally disappear.

Oak wrote extensively on this problem in the time period that it was happening. Some of us continue to think that Oak actually figured out the problem and told BMW!

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If you don't mind my asking, was any sort of thing going on similar to this in the '70s era airheads? I have a '78 R100/7 with only 48,000 miles and no discernible issues like this that I know of. I was thinking of having the heads looked at by an expert who knows these things. However, I am having second thoughts as I hear about all these problems. I am not looking for some "super" performance but simply a reliable, for-many-years bike. I expect to put on around 10,000 miles per year if I am lucky.