Valves and Valve Seats in BMW airhead motorcycles

Valves, valve seats; sick valves/seats; leaded fuels;
guides, valve springs, aftermarket valves, ETC.

This entire article is my personal opinion.

NOISY VALVES:
Noisy valves are USUALLY the result of excessive rocker arm end-play. This can be 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 ovally, and wear of rockers and shafts can create 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 originally for 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. This is particularly so with the earliest pushrods, although that is a very 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. All these things help a bit here and there to quiet the valve gear.

Leaded fuel:
Use of aviation fuels, in the U.S., and possibly elsewhere's, in road vehicles, is likely illegal. Many years ago, when leaded (additive is tetraethyl lead) automotive fuels were the norm, some gasoline's contained ethylene dibromide, which helped flush the lead from the combustion chamber, 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 tetraethyl lead. 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 herein for valve/seat protection will likely 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 needed for protecting the valves and valve seats.

Tetraethyl lead, dangerous if absorbed through our skin when in pure form, is a form of lead previously used extensively in some gasoline's. This 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 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, this is a simplified version of lead usage.

Lead is not good for human beings, 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. Deposits of lead compounds, and other compounds in gasoline, are also left on valves and 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, have 'hot carbon spots' causing pinging (pinking) detonation, ETC. Besides these things, lead manages to get into the lubricating oil, and slowly poisons it. That is one of the reasons, back in leaded fuels days, that one should never get used engine oil all over your hands. Today it is not as dangerous, but there are still nasty's in the oil.

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 is 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. The idea 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. 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, wiping the lubricating effects of the lead, so-to-speak.

BMW had TWO problems. The problems began showing up first on the 1980 and later models. It did NOT show up at that time where folks worrying about upcoming lead-free gasoline's thought it would; the 1979 and earlier (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 seat material introduced in 1980 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 the 1980 and later 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.

The valve SEATS were not damaged but somewhat at the edges, certainly not like the pre-1980 models (which became problems later on). Some machines got valve jobs, and the same bad situation started again. It seems that BMW made an 'improvement' for the 1980 models that made things worse.

The first indication of problems is almost always rapidly closing up of valve clearance settings, ESPECIALLY and PRIMARILY the exhaust valve. This is true for both pre and post 1980 models.

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, 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 the CAST IRON valve seats.   AND, some seats were heat treated better than others, 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 common grade called 100LL, is needed, per gallon of unleaded car gas, for good protection on the early, 1979 and prior 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 likely illegal in the U.S., possibly elsewhere's too.   Still, many who have lawnmowers, etc., with old type seats, add aviation fuel to their tanks.

***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. 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 that required to boost octane any appreciable amount. Using the 4 gm/gal specification type of aviation gas, 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, likely illegally in the U.S., do use a tad of aircraft gasoline (100 or 100LL). It only takes a minute amount of lead to protect the valve and seat, 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 phaseout, in many instances. 'Race' additive WITH lead is still 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 few cupfuls every few tanks, or a cup or so per tank, apparently does the job, as mentioned earlier herein. ...So...if you have a 1979 or earlier, and are beginning to see exhaust valve closure, you might add a cupful of aircraft gas, to the tank. Or maybe a ounce per gallon. Aircraft gasoline's are found mostly in a grade called 100LL, meaning 100 octane (aircraft type measurement) Low Lead. There is a high amount of lead in this gasoline. 100 grade (not with the LL designation) may also be found. 100, versus 100LL has considerably more lead, and less is needed, by half. A grade that used to be seen now and then at small airports is "80/87" (NOT if marked automotive or road fuels, which is available at some), which contains a fair amount of lead. ANY of these LEADED grades will work fine as an additive for the 1979 and earlier airheads...with the 100 [NON-LL] grade being the better, as less is needed. Again, I must caution, that this usage is likely illegal, and a small amount of deposits, and slightly less spark plug life is likely.

If you have a 1980 and later, 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.

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, where unleaded fuels were used by those with catalytic converters in CARS.

Unless an additive states specifically that it contains lead, 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.

In early 1989, most major gasoline producers suddenly eliminated leaded fuel entirely. With no lead here and there, and underground tanks being flushed 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 problems, for 1979 and prior; and, 1980 through 1984.......but BOTH problems end up causing closing of exhaust valve clearances.

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.

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

The fix for BOTH problems is to put in the latest VALVE SEATS that BMW now 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 airheads with valves and/or seat problems prior to 1985 is new valve seats of the 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, 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.

Some more technical information...READ THIS, as it covers a lot of questions often asked!:
1. The Luftmeister, CC products, and some others, known as S.L., 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 Black Diamond products are ""OK"". These are a one-piece SS valve, that is hardened at those keeper slots. There are some other 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.   I think the genuine BMW valves are BETTER and WORTH the extra money.

3. The BMW intake valve is a one-piece SS. 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. It is very rare for the BMW exhaust valve to fail.  The tip and keeper slot hardness seems GOOD, or even superior.

4. 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 BMW valves IF USED WITH AFTERMARKET GUIDES, properly installed.

5. SEATS:   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.

6. Sort of repeating prior information, for emphasis here: Use of aftermarket one piece SS valves is a BAD idea...if using BMW valve guides, and in some cases may be a bad idea period.    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 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, and you may want to use a different valve guide material too.

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.....I am NOT one of those persons.

Valves, valve seats, 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.

BMW valves: These are amongst the very best for your bike. BMW valves are very pricey. There are good valves from brands such as Federal Mogul (stems are hard chrome plated) and BD (Black Diamond). The BMW EXHAUST valves are two piece design, with chromed stem for very long wear and no galling. The intake valve is much less pricey from BMW, it is a good valve, under vastly less stress, other valves are also OK here. On the BMW exhaust valve, the tulip is softer, but more heat resistant and corrosion resistant. This BMW exhaust valve has a type of stainless steel in the tulip. AVOID, especially, MOST aftermarket one-piece SS alloys. They may well swell-up in the guides, break, and do other nasties. NOTE!....I have thought about use of aftermarket valves many times. A question of using these comes up often on the Airhead mailing LIST....especially for the name Black Diamond. I think that with the 'right' valve guide material, seat material, and valve material, one can use these successfully. I just will not try, since I don't wish to experiment in this area. If a valve lets go, or seizes in the guide, you can have VERY serious engine damage. Ted Porter (Beemershop) has tested and used other than BMW parts quite successfully, and sometimes with problems...and he has settled on those parts HE TRUSTS....and I have NO quarrel with him....ask him about using BMW exhaust valves, and see how he replies! Oak uses only BMW parts.

I suggest you use BMW valve springs.

I do NOT use BMW valve GUIDES....for reasons noted well above.

NOTE: BMW valve seats are very good (the old bad ones are NLA), but may not fit if you have a SIZE problem....then, any decent modern seat for unleaded fuel is OK.....Tucker, Martin & Wells for examples. Fitting valve seats is a tricky job, best done (as is ALL BMW airhead head work) by someone with VAST experience on BMW airheads (not just on VW or Porsche, etc., air cooled engines). Do NOT take this caution lightly!!!

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. They are not really needed, in my opinion, with a proper valve job with the proper parts.

NOTE!.....BMW valve guides MAY NOT be the best choice, as they are sized to fit right from the box once installed, and thus will not be perfectly round and UNtapered, after installation. I prefer aftermarket guides, which can be precisely fitted and honed/reamed. However, some experts disagree, and feel the BMW guides have advantages. Still, my feeling is that a good aftermarket guide, properly installed, is better than the BMW guide.

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, 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 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.

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: " "

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