Valves and Valve Seats in BMW airhead motorcycles

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BMW Airhead Motorcycles: valves; valve seats; sick valves/seats; leaded fuels;
valve guides; valve springs; valve seals; aftermarket valves; bead-blasting.

This entire article is my personal opinion.
(but I DO have some other folks opinions here, and identified!!)

NOISY VALVES:
Noisy valves are quite often the result of excessive rocker arm end-play due to improper end play adjustment. On the stock valve gear models through 1984, the rocker blocks are usually slightly adjustable during tightening. Early gear, the /5 in particular, are vastly more adjustable, and they are more tricky to set up as they can be moved all about and need some extra care with alignment before tightening the head nuts.   The /5 has bushings in the rocker arms, and they wear in an oval pattern, and wear of rockers and shafts can create noise.   Worn valve guides can lead to increase noise. Wear on the later needle bearings-equipped rocker arms is usually very low. As valve seating area gets wider from high mileage (let alone someone grinding the seats and valves with too wide a contact area) the wider seat contact area causes an increase in noise.   Fairing equipped models will SOUND louder.   It is NOT unusual to hear one cylinder louder than the other, and not unusual for them to get louder as the engine heats up; occasionally the reverse is true. Increasing loudness after warm-up is particularly so with the earliest pushrods, although that is a small part of the noise increase. There are rubber pads available to insert into the fins which do help some in reducing the fin-ringing. See the article: quietingpads.htm

The proper amount of rocker end play is for OIL FILM movement when rocker moved up and down (not under tension). Rocker must not be so tight that it cannot move throughout the entire lifting rotary motion (back the adjustment WAY off to see).   Rocker must move smoothly, no binding.

Proper torque on the 6 nuts is important. They must be tightened evenly, in a cross-pattern, ending up at 25 footpounds on an ACCURATE torque wrench. The FOUR rocker nuts and stud threads are OILED.

Some of the needle bearing types were improperly made and gave problems....Oak did an article on that some time ago, in AIRMAIL, September 2004.

This website has information on how to move the /5 bushed rockers to other positions, and gain more life before needing re-bushing. see: headassy.htm which has a lot of information on the heads.

Leaded fuel, use, implications, etc:
Use of aviation fuels in the U.S for on-road use is illegal. Many years ago, when tetraethyl lead (TEL) automotive fuels were the norm, some gasoline's contained ethylene dibromide, which helped flush the lead from the combustion chamber and under the exhaust valve tulip head, reducing deposits. Still, a considerable amount of lead deposits occurred at idle and very light throttle situations, where the heat in the combustion chamber was not high enough to burn off and flush the deposits. It is the author's belief that Chevron's Techron secret ingredient was this chemical, or something similar to it. Techron has been reformulated more than once, and the author does NOT KNOW if lead scavenging substances are now in Techron...or ANY other gasoline or additive, EXCEPT aviation fuel. Adding aviation fuel to road gasoline in the amounts noted later herein for valve/seat protection will not result in excessive deposits in cylinders or damage spark plugs. NOTE that the amount of lead in leaded car gas many years ago was quite high, to increase octane, and vastly LESS was actually needed for protecting the old valves and valve seats.

Tetraethyl lead, also called TEL, is dangerous if absorbed through our skin when in pure form, which you likely will never see or be exposed to. TEL compound has TWO major effects. First, in sufficient strength it raises the octane value, very important in WWII aircraft engines that were of very high output per cubic inch and flown at high altitudes, and especially those that were supercharged or turbocharged, or both.   The original purpose for using tetraethyl lead was specifically for raising octane. Some of those aircraft engines required 145 octane gasoline!! Usage for that purpose was carried forward for decades for cars because it was cheaper than more costly and sophisticated refining methods, even when the lead (TEL) was sold expensively by the then monopolistic Ethyl Corporation.   Many decades ago, premium gasoline's were simply called "Ethyl". There is a lot more to that story, that is a simplified version of TEL sales and usage.

Lead is not good for human beings nor animals nor birds, whether breathed in from the air, or by skin or other contact. It is particularly bad for young folks, as it has many bad effects, especially on the brain. Octane-raising strengths of lead additives in particular are responsible for short spark plug life. Lead conducts electricity, and is slowly, sometimes not so slowly, deposited in some sort of conductive metallic form on the center ceramic insulator of the spark plug, and when enough is deposited, it will electrically short out the spark plug; usually irregularly and annoyingly causing misfires and wasting fuel, not to mention accelerating all sorts of combustion chamber deposits. Deposits of lead compounds & other substances found in gasoline are left on valves, in the combustion chamber and on pistons. Some even manages to get inside valve guides, promoting wear. These combustion chamber deposits can raise compression ratio, cause some other types of wear, worsen 'hot carbon spots' causing pinging (pinking) detonation, ETC.   Lead manages to get into the lubricating oil via blowby, and slowly poisons the oil.   That is one of the reasons, back in leaded fuels days, that one should never get used engine oil all over your hands (besides the fact that the oil got contaminated, and hence the 3,000 mile change intervals back then, often still promoted today, but NOT by car company's, who know better!). Today it is not as dangerous, but there are still nasty's in the oil from combustion by-products.

The 'seat' and 'valve' protection effects of TEL were something noticed later on, after WWII [I think]. Tetraethyl lead in vaporized form leaves a microscopic layer of lead on the valve and seat; some folks call this 'cushioning'. It was pretty much originally accepted that this effect was to prevent microscopic welding. Little bits of carbon might help promote that welding, and the microscopic little places WELD the valve and seat. Again, a few microscopic places. Then the valve lifts again and some microscopic metal is removed leading to pits and valleys. That this really happens in our Airheads is debatable. Lead is, at very high temperatures, a LUBRICANT, AND A TERRIFIC CONDUCTOR OF HEAT. Saying all this another way, the original belief by many was that a bit of lead makes the seat and valve much less likely to weld at microscopic and scattered points, and that the valve head heat is more readily transferred to the seat by being 'lubricated' by lead. Lead was thought to generally totally prevent this.

However, new theory has it that in our pre-1980 airheads, it is the normal rotation of the valves (you DO know that the offset rocker arms cause the valve to rotate, and also cause egg shaped wear on the valve guide?) that is causing the wear.   That is, actually, an additional factor, and does not necessarily negate the original belief.

BMW's Airhead problems:

BMW had TWO problems. The problems FIRST began showing up on the 1980 and later models. It did NOT show up right away, as many thought it would....on the 1979 and earlier models with cast iron seats. BMW changed the 1980 and later seats, IN ADVANCE PREPARATION for the soon-to-be ONLY type of car gas, UNleaded gas. In the U.S., lead-free gasoline's were introduced in 1989...or, better said, road-use leaded gas was outlawed. Yes, I know Amoco had unleaded gas earlier, but I am talking about the entire U.S., by LAW.

The new valve seat material introduced in 1980 by BMW was a SS, high nickel-chrome alloy. NOTE that this seat material can be identified by a SINGLE scribed line on the inside; and, the later 1985+ PROPER material valve seats have TWO scribed lines. Problems with 1980 to 1984 models became more and more evident and the dealers and BMW blamed things on poor maintenance and rider abuse for the problems showing up on U.S. motorcycles. Many of these engines developed deformed and overheated exhaust valves...some were swallowed up in the seat bore. The R100 models were the worst. They develop more heat than the smaller engines. There were other contributing factors, including lean running engines, the pulse-air injection system, high power output on some models, etc. (note: 1980 is used here, but you may also think of it as 1981 to 1984)

These 1980-1984 valve SEATS were not damaged but somewhat at the edges, certainly not like the pre-1980 models (which became problems only later on). Some 1980-1984 Airheads got valve jobs, and the same bad situation started again. It seems that BMW made an 'improvement' for the 1980 models that made things MUCH worse. There is a German word for that sort of thing: schlimmerberbesserung

Sometimes, particularly on the smaller engines of 1980-1984, problems with the valves/seats did not show up for quite some miles.

The first indication of a problem is almost always rapidly closing-up of valve clearances, ESPECIALLY and PRIMARILY the exhaust valve. This is true for both pre and post 1980 models, which differ in the cause.

Note that a BMW airhead with mechanically sound valve gear: good seats, valves, guides, of the later proper materials (or, earlier parts with leaded gasoline's) will normally not have valves closing up more than about .001" to .002" per 5000 mile adjustment interval.   Those riders that like to use the area near or at red-line rpm, may find the valves closing up a bit faster. In fact, with a good top end condition, closing up of as little as .0005" per 5000 miles is NOT unusual.

Meanwhile, as the 1980-1984 bikes were having problems, the 1979 and earlier bikes, were still mostly OK. Everyone 'KNOWS' that cast iron seats won't hold up to unleaded gasoline...right? What was going on? Well, there was plenty of lead still around, in the distribution system, inside tanks, etc. It takes only a minuscule amount of lead to protect CAST IRON valve seats.   I also believe that some seats were heat treated better than others, and since the unleaded problem was not known, there was no reason to tighten heat treatment specifications (I am NOT sure this last sentence is correct, it COULD have just been poor quality control).

***About 3 or 4 ounces of aviation leaded gasoline, in the commonly available grade called 100LL (100 octane Low Lead), is needed, per gallon of unleaded car gas, for good protection on the 1979 and earlier airheads. On a practical basis, less than this amount seems OK, and many have had good results by simply adding a cupful (a cup is 8 ounces officially, but in practice is 5-8 ounces) every few tankfulls. NOTE that this usage for road vehicles is illegal in the U.S.   Still, many who have lawnmowers, etc., with old type seats, add a small amount of aviation fuel to their tanks. Some owners of pre-1980 Airheads with the original type of valve seats do this too. 1980 was a crossover year, so some 1980 models are helped.

***For the technical types out there, wishing more exacting information, aviation fuels containing either 4 or 8 grams of tetraethyl lead per gallon are, or were, common. Leaded fuel for airplanes was typically available in 87 octane, and low and high leaded 100 octane. Today, only 100LL is likely to be found at airports. It is commonly accepted that approximately 0.1 gram (some say up to 0.3 for high protection) of tetraethyl lead per gallon is enough to provide reasonable valve seat protection. This is FAR LESS than the amount required to boost octane any appreciable amount. Using the 4 gm/gal specification type of aviation gas (LL), only .025 gallon of aviation gas is needed per gallon of unleaded car gas. A gallon is 128 ounces (U.S. measure). Thus, only 3-1/4th ounces of aviation gas per gallon of unleaded car gas is required for acceptable protection. Frankly, less is needed, as aviation piston engines work very much harder than our airheads (normally).

Some people do use some aircraft gasoline (100 or 100LL) as an additive. It only takes a really small amount of lead to protect the valve and seat (SOME 1980, but all PRE-1980), and it need NOT be in every tank, it was residual amounts in tanks and delivery systems that kept 1979 and earlier bikes in good condition for YEARS after the lead phase-out, in many instances. 'Race' additive WITH lead MAY still be available, expensively. However, you need so little lead, that aviation fuel cost becomes very small in actual usage. Aircraft gas, typically costing 'only' perhaps twice as much as car gas, can be stored in a metal can for many years, it does NOT gum up like car fuel does.....and a cup or so per tank, apparently does the job, as mentioned earlier herein.   ...So...if you have a 1979 or earlier (1980 in some instances), and are beginning to see fast exhaust valve closure, you might, illegally of course, add a cupful of aircraft gas to your airhead's tank when filling-up.

If you have a 1980 and later (with a FEW exceptions for 1980), this lead will NOT stop valve recession as far as I know, and it is not clear to me if it will help in the slightest; I've never run tests. The best fix is a top end job with new valve seats, those seats that BMW sells.   It is tricky to properly install the seats, you need about .005 to .006" of interference fit, and you need to heat the head to about 500°F...and KNOW what you are doing. Most any auto machine shop is totally INadequate to do this job ....you need someone like Ted Porter, Oak Okleshen, etc.

Why did not BMW do something sooner?   My belief is that BMW did NOT BELIEVE the problem REALLY existed, with no reported problems in Germany.

Unless an additive states specifically that it contains lead, or TEL, it is unlikely to do ANYthing to help the 1979 and earlier (or later models). There are some possible exceptions, some tout ValveTect. I have no personal testing information. Some marinas carry ValveTect, some say it is an acceptable substitute for lead. Most other additives are worthless. I have not personally tested ValveTect. Remember: adding TEL (lead) does NOT work on the later valve seat problems, it works only on the models before 1981 (and, with the caveat that not all 1980 models will benefit).

1979 and earlier:

In early 1989, most major gasoline producers suddenly eliminated leaded fuel entirely. With underground tanks being flushed by being used with new type unleaded fuels, it was not long until the 1979 and earlier bikes were having problems. Major wear patterns, sharp and well defined steps in the valve SEAT. The exhaust VALVES in the 1979 and earlier models were generally OK. The 1980 and later models continued to show damage as previously described, mostly to the VALVE, as the valve was unable to cool enough, as the seat did not absorb and transfer the heat. NOTE that SOME pre-1980 bikes had no problems. Apparently BMW had more than its share of problems in heat treating the original cast iron valve seats....as previously noted. The paucity of problems is particularly so on the cooler-running smaller bore models. Keep in mind these two very distinctly different causes for 1979 and prior; and, 1980 through 1984.......but BOTH problems end up causing closing of exhaust valve clearances. Keep in mind, also, that the smaller bore Airhead engines have fewer problems, with less over-all heat developed.

Fresh valve jobs were not a lasting repair, problems returned shortly thereafter.

SO,,,,there were TWO distinctly different problems, depending on whether the engine was a 1979 and earlier, or a 1980 and later. AND, sub-problems, in that SOME 1979 and earlier cast iron seats were 'harder' than others, and that some engines ran much hotter. SOME smaller bore engines of 1980 and later did not have problems, or not soon.

>>>>The BMW 'production fix' occurred about 1985.<<<<

The fix for BOTH problems is to put in the latest VALVE SEATS that BMW sells. This material has a vastly improved thermal conductivity, and is immune to not having lead in the fuel. These valve seats are very good, and have TWO scribed lines inside. The EARLY 1980's 'bad' seat material can be identified by a SINGLE scribed line on the inside; and the UPdated seats have TWO scribed lines! NOTE that the FIX for ALL the prior-to 1985 airheads with valves and/or seat problems is new valve seats of this 2 scribed lines type.

****It is possible that using a very small amount of tetraethyl lead in today's lead-free gasoline MIGHT make our old 1980-1984 OR the 1985 type of updated valve jobs last longer, due to the better heat transfer of the lead......but I have no information, and this is pure off the wall speculation, without a shred of proof on my part. That lead does help the pre-1980 original valves and seats is unquestionable.

The new seat material is not what folks generally think of as SS, rather, it is a 'tool steel'. Sometimes the early valves, if in good condition, are reused during the seat installation and 'valve job'.

Some more technical information...covering a lot of questions often asked:

1. The old Luftmeister, CC products, and some others' valves, are a ONE PIECE stainless steel valve. If you use such valves, they are usable (that 'usable' does NOT mean I recommend them!) with Martin & Wells Martite or Welltite seats. They have a chromed stem that wears OK in the guide, and a Stellite tip. They are NOT hardened in the keeper slot area...and so the keeper slots wear, moderately quickly. The slots open up such that the valve cannot be removed from the guide without laboriously filing the end of the valve. The manufacturer, or others, may suggest grinding the keepers until the valve no longer rotates...DO NOT!! Guide clearance is critical for these valves. I highly recommend never using these valves and seats, etc., in combination.

Genuine BMW two-piece welded exhaust valves have better tip and keeper slot hardness and wear better than many other valves.

2. Kibblewhite's Black Diamond products are supposedly ""OK"". These are a one-piece SS valve, that are NOW supposedly hardened at those keeper slots. I am not a 100% believer. I think the slots wear excessively. There are some things nicely done on the valves, such as a machined tulip and a polished swirl finish. The tip is Stellite, and works well with the Martin & Wells seats...although Kibblewhite also has matching seats of their own. Due to the hardening process, the valves are black, and do not have a chromed stem. The guide wear will be a bit faster due to that, and might even gall in the guides. Do NOT grind the keepers to keep the valve from rotating.

I think the genuine BMW valves are MUCH BETTER and WORTH the extra money.....because there HAVE been catastrophic failures of the Black Diamond valves (There have been a few rare failures of BMW valves too, typically they were in the early eighties, with the bad valve seats, so the valves had been overheating and deforming for a long time). Here is a situation where the BMW exhaust valve costs a lot more money but I think it is wise to spend the money.

Repeating this differently, and adding a bit more: Reports have come to me that Black Diamond valves are not recommendable. The reason is that they have a thin coating on the stems that wears off, and the stems are soft. The reports to me that this problem occurred... were with AMPCO guides.   The type of guide might well be SOME of the problem.
There are problems with installing some valves. Minimally knowledgeable shops may grind the keepers so the valve does not rotate. That strikes me as really wrong.

3. The BMW exhaust valve is a TWO-piece, inertia welded, and pricey, but VERY good quality and performance. It is VERY rare for a BMW two-piece exhaust valve to come apart in service...contrary to rumors pushed by other makers of valves.    This BMW chromed valve wears well in the guide, and the SS head works well with the later (1985+) BMW OR Martin & Wells seats.  The tip and keeper slot hardness seems GOOD, or even superior.

4. The BMW intake valve is a one-piece type of SS, and is a good valve. Others can be substituted. Be sure the guide material is compatible with the valve.

5. GUIDES:   here is where I don't like the BMW parts.   BMW valve guides come already sized for stem clearance. This makes it convenient and fast for shops without proper guide honing and measuring equipment...but makes for a so-so valve job.   After the BMW valve guide is installed, the inner diameter of the guide is larger where it sticks out of the head, and smaller inside the head metal area. If you hone a BMW guide until round, you probably will end up with excessively wide clearances.   Thus, it is better to use AFTERMARKET guides with smaller I.D., so that after installation, they can be honed round, and will have correct clearance, and last a long time with no oil burning. BMW does NOT make such a guide. Thus, I recommend genuine BMW valves...BUT, USED WITH AFTERMARKET GUIDES, properly installed.

6. SEATS:   This is one more place I think the BMW parts are lesser parts, primarily because BMW valve seats are PRICEY. Seats made in the U.S. are fine, and you can have them made to order. Installing seats requires a real professional and very experienced person, and NOT just any old automotive or motorcycle machine shop, etc., is capable of doing the proper job.    For the nerdy, the heads are heated close to 500°F, and fitment is made for 0.005" to 0.006" interference-bit.

7. Repeating prior information, for emphasis here: Use of aftermarket one piece SS valves is a BAD idea...if using BMW valve guides. BMW uses a high quality multi-piece SS exhaust valve....with the various parts materials selected for the best performance in the area being used...although I do recommend aftermarket guides...and aftermarket seats are OK if the proper type of material and properly fitted. SS ONE piece valves may swell up in the stems area, seize in that area, stop rotation. Stems will gall, tulips and seats will deform. Sometimes the swelling is so bad with SS one-piece valves that they are not easily removable, and might drive your machinist nuts. One piece SS exhaust valves are a BAD deal...do NOT use them, unless you match them to proper valve guide material. If you want to try this, you are on your own. There is also the problems of the keeper slots at the valve tip with some non-BMW parts, as noted previously.

8. If your valve springs are not in good condition, and do not meet specifications....and you use high rpm, ....you could have valve float, the valve could strike the piston and you will have a huge mess on your hands. There is a LOT MORE TO SETTING UP OF A TOP END.....this is just one mention of things that need to be checked....including that the springs do not bind up at full lift.

There is more information on valves, etc., in the next section.

There are only a FEW trusted experts on BMW valve gear problems, such as Ted Porter at his Beemershop in California; and, OAK in the Chicago area.

There are some that feel that a way around all these various problems is to use such as Black Diamond valves, and AMPCO 45 guides.....AGAIN....I am NOT one of those persons.

Because this valve situation is controversial, I thought it would be a good idea to offer input from a VERY experienced Airhead wrench, who personally does a lot of head work.
The following is very direct and to the point, and is trustworthy information. This was the result of a thread on the Airheads List. This is long, but I suggest you read it.
The rest of MY valve article continues after this. I have done editing ONLY for minor ease in reading and for spacing and line length. Anything in parentheses and RED is MY comment.

This below reply was by Ted Porter, www.beemershop.com

This is long so get comfortable if you're interested in my opinion.
>
> A customer pointed me to this thread. I'm sorry to say I haven't had much
> time to be on the List lately, any of you who have visited the shop know how
> busy we can be. I was encouraged to respond due to my extensive history
> overhauling BMW heads and my experience with all the different valve, seat
> and guide materials that I've used over the decades. I've used all the stuff
> out there and over time have enjoyed the benefits of seeing those parts
> again many years and many miles later. I've been doing this work for a very
> long time with my own hands and eye balls, on BMW motorcycle heads
> exclusively, I thought my opinion might be useful.
>
> I wish I still believed in the BD valves. I was once a distributor of their
> product and a vocal promoter. It would benefit my business greatly to
> install BD valves because the factory is right up the road from my shop and
> it would be a hell of a lot easier for me to sell those products. I didn't
> decide to start importing valves from Germany because I like dealing with
> all the headaches associated with that process, but rather because that's
> how I get quality two piece exhaust valves on my shelves that meet my
> standards without having to pay $100.00+ per valve from BMW. The BD
> stainless one piece valves are much cheaper, have very nice profit margins,
> and you can order just a couple at a time and let Kibblewhite inventory the
> parts for you which significantly lowers use of your capital. I believe many
> shops are compelled to use the product for these reasons. I was once a loud
> promoter of the product as well, however I started seeing some limitations
> and since overhauling heads is my industry, I did my homework by talking to
> the valve manufacturing experts here and overseas. There was definitely a
> consensus.
>
> To answer the OP question, BMW started using the two piece valve design many
> moons ago, long before the /5. For the exhaust valve it was determined that
> one material is better at the stem and the tip (steel) and a different
> material is better in the combustion chamber (stainless). It is more
> expensive to make the 2 piece exhaust valve but I agree with the engineers,
> there's a strong argument for the design. Note, this is only true with the
> exhaust valve. The intake valve is a one piece steel design (not stainless)
> and works without problems in that application due to the cooling effect of
> the intake charge.
>
> I am not an engineer, but here is what the experts in this field explained
> to me:
>
> 1.The stem must be hard chromed so that it will wear well in the guide
> without material transfer and galling.
> 2.The tip must be hardened so it can be smacked by the rocker arm over many
> cycles without failure.
> 3.The keeper slots must be hardened to deal with the rotating design of the
> valve (the keepers do not grip the valve but merely secure the valve and
> upper spring cap by the grooves in the keepers and slots in the valve and
> allow the valve to spin. The rotating valve helps the seat and valve stay
> clean and makes them both last longer).
> 4. The valve face must deal with the high temperatures generated by the
> exhaust gasses.
>
> Steel was selected for the stem because it can be "through hardened" at the
> tip and keeper slots, and the stem could be hard chromed. Stainless alloy
> was selected as the best material for the valve face in the combustion
> chamber. The two pieces are inertia welded together and every BMW motorcycle
> on the planet for the last 50+ years has this design. The two materials do
> not work well in the reverse roles. The stainless material is not well
> suited for the stem or tip. It is soft and cannot be through hardened, the
> keeper slots can fail, and the tip will not survive the pounding of the
> rocker arm, The steel of the stem would not work well under the heat stress
> of the exhaust valve face. Therefore it was determined that one material
> would not work well long term in both environments but, and here's the
> clincher, the one piece stainless valves are a hell of a lot cheaper.
>
> The early one piece stainless valves we were experimenting with in the early
> 1980's developed well known problems. The early designs would not work well
> with rocker arms and required separate caps (known as lash caps) installed
> on the tips of the valves. The later designs were improved by welding a
> .060" thick stellite wafer on the tip to deal with the rocker arm contact.
(BMW exhaust valves are through hardened at the tip/stem and do NOT need, nor do they have, Stellite wafers at the tips)
> Regarding the growing concerns about keeper slot failures, we were told to
> grind the keepers so that the faces no longer made contact so that the valve
> would no longer rotate. I thought that was pretty lame and started looking
> for alternatives.
>
> The BD valves looked promising. We were told they solved the soft stainless
> problems through a process that hardens the surface of the valve and turns
> the valve black (hence the name) and by installing the stellite wafer on the
> tip of the valve. However the valve stem could not be hard chromed. I used
> these valves for many years, then I started seeing the problems; material
> transfer from the guide to the valve stem. We were told the galling problems
> were solved by the addition of a "dry film lubricant" impregnated in the
> stem, but inspection showed that the surface treatment would wear away. I
> still saw the galling and became concerned about seizure. Then we were told
> to try running wider clearances, which I thought was a poor solution. This
> is probably why some machine shops are now using cast iron guides to deal
> with the lack of hard chroming on the valve stem (although Kibblewhite
> suggests using their Ampco 45 silicon bronze guides). However cast iron does
> not shed heat well and it is softer then the modern manganese silicon bronze
> guides so I consider it a poor compromise. It finally became obvious that I
> was chasing my tale trying to sell a cheaper valve that would perform as
> well and be as durable as the two piece design and it became clear why the
> valve manufacturers who make valves for Audi, Porsche, Saab, BMW, M-B and so
> on are all using the inertia welded two piece exhaust valve.
>
> For many shops the BD valve will become the default. They are waaaaay
> cheaper than buying valves from BMW or importing valves from Europe. Many of
> these shops also work on automotive heads, or they are multi-brand
> motorcycle machine shops. They are not so heavily invested in just BMW heads
> and it doesn't make sense to invest capital in the large minimum orders
> required to import valves from the manufacturers in Europe (my first order
> was financially painful). BD valves are the simple solution for many
> businesses, however in my experience and opinion, they are not the best
> solution for long term use in a street bike.
>
> I looked at a pair of customer heads not too long ago that had been
> overhauled by one of those automotive machine shops turned BMW experts. The
> heads looked very pretty which makes many of you say, "just got my heads
> back and they looked great". What I saw was BD valves with over .003"
> clearance at the guide (probably to prevent galling) keeper halves no longer
> touching each other because they had been ground to prevent valve rotation
> and lower the risk of keeper slot failure, and seat eccentricity well over
> .005". Yeah they looked real pretty but the head work was crap. I asked the
> customer if he had been told that his keepers were going to be modified to
> stop the valves from rotating and he said no. I thought that kinda sucked.
> If you have stainless valves, have a look at your keepers where they sit in
> the spring cap at the tip of the valve just under your rocker arm, the two
> halves should be touching each other. If there is a gap, your keepers have
> been modified to grip the valve and prevent valve rotation so the keeper
> slots in the stainless valves don't fail. If anyone is interested in seeing
> an example of the keeper slot failure in a stainless valve I have a good
> photo to share.
>
> To those of you that say "I have them in my bikes and no problems", for the
> vast majority of the heads I overhauled with BD valves in the 1990's there
> were no problems that the average rider would notice, but you have to look
> deeper. If you take them apart and inspect them with educated eyes and
> measuring tools, you will see the limitations. Sometime this manifests in a
> seized valve and the head popping off, other times your head work will just
> not last as long because there will be more wear in the guide, and again
> there is the keeper slot issue which still existed in the treated valve.
>
> Problems with the stainless valves in street bike applications have been
> well documented. Perhaps some of you who've been around long enough remember
> the big article in the BMWMOA news magazine back before the internet about
> the heads popping off the stainless valves. I also believe someone named
> Kevin on this list created a website devoted to the problems he was having
> with his stainless valves, and there is also someone else on this list who
> sought out my opinion in the past who had similar stainless valve failures.
> Now it has come up again, this is pretty old news. Yes, I have seen the
> factory two piece design fail at the weld, but considering the sheer numbers
> of these valves in use, that percentage is extremely small. The number of
> one piece stainless valve failures that I have seen and heard about is
> exceedingly higher and there are far less of them in use. You do the math.
>
> I'm not interested in an argument with any persons or shop using stainless
> valves, sell what you want to sell, that's your prerogative. My hope is that
> there is room on this list for another opinion from someone who is arguably
> the most experienced head rebuilder in this discussion. For those of you
> doing your homework, you now have my opinion to add to the mix.
>
> Cheers,
> Ted Porter
> www.BeemerShop.com
> www.facebook.com/beemershop

Valve seals, valve guides and valve springs:

>>>seals are not really needed on stock BMW valves and valve guides!
1980's BMW 733/735 cars 11-34-1-273-501
Ones not requiring any machining....for 8 mm only: FelPro, for the Opel 1600 cars.
The blue dot on the valve springs goes towards the head.
Take a look at Felpro SS70816, and use only the INTAKE ones.
I have heard that the design of these has changed, and they no longer fit properly, unless the guide is machined. Even then, the use was a stop-gap measure for those that installed SS one piece valves in BMW guides. This is highly recommended AGAINST.

NOTE!.....one piece SS valves, such as sold by a few unmentionable companies, do NOT match/mate properly with BMW valve guides, and besides the problems noted, above, you may have serious oil burning problems. Hence the use of the valve seals. These are not really needed, in my opinion, with a proper valve job with the proper parts.

BEAD BLASTING:

While many folks have gotten away with this, my personal opinion is that you should NOT bead blast heads (nor cylinder outsides) using the normal sand-type blasting materials. No matter how carefully one masks and cleans up, small abrasive particles manage to get lodged in crevices or the metal surface, may come loose later...and abrade cylinder walls...valve guides, pistons, etc....and get into the oil...and the bearings. They may well IMBED themselves, doing considerable damage over time! If you simply MUST blast, use walnut shell or soda or CO2 blasting; which are less permanently abrasive. Heads (insides) are best cleaned chemically...it takes a week or so, but is SAFE!! The recommended cleaner is Gunk brand Hydroseal. Some are using strong solutions of Simple Green, which may eat into aluminum, but so far I have had no bad reports in overnight use, in 1:2 mixtures with water.

Additional Information:
1. http://www.chm.bris.ac.uk/motm/leadtet/leadh.htm will have some technical information on lead and MTBE used in fuels, and some URL's/links.

Revisions:
01/26/2008: incorporate all previous revisions and also move to article 60 sub-section 5; and update for clarity
06/26/2008: Minor updating
09/08/2008: " "
03/24/2009: revised here and there for clarity.
04/16/2011: update for valve noises, and add links to other articles of mine that are pertinent.
04/28/2011: Clarify a few details, clean up some wordiness. Were no errors corrected.
08/29/2011: Add section on Ted Porter's commentary from the Airheads LIST
04/03/2012: Check over article. Clarify a few details. Clean up article a bit.

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