The discussion boils down to this--do you want to spend the money to change to hardened valve seats? If you ride your Airhead 1000 miles per year, the answer is probably no--just check the valve clearances periodically and adjust as necessary. If you ride your Airhead 20,000 miles per year and are adjusting valves 5 times per riding season, you proabably want to make the change.
True, riding mileage may help make the decision. I'm not a big rider...100K miles in the little over 30 years I've had my /7. Pretty far short of 5K per year. But the last few years, I've really been wondering what was down there...was she going to make it the next season. What was that noise? What if...? I'm glad I've done it...I have good confidence in the change over. Peace of mind from here on out...until I have to worry about something else...like the timing chain!
I read something that Tom Cutter posted on the Airheads email list. People were discussing the idea of just monitoring the clearances and making the decision that way. Some have wondered about how many threads were showing on the rocker adjuster. He pointed out that the thread pitch is 1mm on the adjuster. So, if you've had to make one revolution of that adjuster, the valve has slid 1mm...which Tom said is one-half the width of the valve face. Think about that! That doesn't sound like much, but that picture in my mind screams problems and it might be sooner than one thinks.
A rather article that covers the various valves and seat problems with the Airheads, and includes a lot of information
on leaded fuels, and aircraft gas as an additive, ETC (LOTS of "ETC") is here:
snowbum (who rarely is on the MOA.org forums)
you an still get Bardhal Instead of lead gold, it contains MMT as an octane booster which also protects valves. I have used this for years before a got some modern stuff, and it works very well as octane booster and as a valve protector.
It is true that Bardahl contains MMT (methyl cyclopentadienl manganese tricarbonyl); and that it DOES help with protecting the Airhead pre-1981 (or pre-1980) exhaust valves and exhaust valve seats. It is, probably, the closest thing to TEL (tetraethyl lead) for protection. It isn't as good.
It needs reasonable concentration for its effects. BTW....few know this....but it is not only pre-1980 Airheads that need TEL or some at least reasonable additive (if the valve seats are stock); but, the very earliest K bikes had susceptible valve seats too. Luckily, they are water cooled, and vastly less susceptible.
Sooner or later, the early Airheads will need a top end job, at which time the seats really should be upgraded.
That is only a very partial statement. It takes a LOT of lead to boost octane, and octane boosting is not the problem with the old engine's valves and valve seats. Pump 91 in the USA is usable for our old bikes.
Ethanol is a nice fuel, at near 100%...but you need a vastly larger tank, huge jets or a very modified FI system, etc. Ethanol was pretty good for racing, years ago. Fuel mileage was atrociously low. My Gold Star ran ethanol, and near 1500 jet size...that is a huge size. The Brazilians are quite familiar with exceptionally high concentrations of alcohol in their fuel.
In the real world for us:
Ethanol is added to gasoline all over the USA. Yes, tthanol itself has higher octane inherently, but only if it is running to the correct mixture!...which is VERY MUCH RICHER. In carbureted engines IN PARTICULAR (but can affect some FI engines), just having ethanol in the fuel like we presently have, LEANS the fuel mixture, so the mixture runs leaner, and usually HOTTER, making things WORSE. You have to enrichen the mixture a bit ('a bit' for 10% ethanol) to burn it quite properly, and almost no one will be doing that for their road bike. Modern FI handles it pretty well. Older FI bikes are slightly iffy.
Further, this product, called gas-O-hol by most, will give you LESS fuel mileage, and stores poorly, so if you do not use the motorcycle often enough....you can have fuel problems. On top of which, the co-solvents only hold so much moisture from the air....and dew condensation inside the fuel tank can cause water droplets to form, fall to the bottom of the tank, to do their nasty deed on the tank itself. This happens mostly with steel tanks, but DOES affect aluminum tanks. Plastic tanks are NOT immune, as alcohol attacks some plastic materials...including quick disconnects! Ethanol rots some types of rubber compounds. Fuel hoses, filter media adhesives, O-rings, etc. Ethanol in fuel is nothing but a government-mandated boondoggle. It's production has a nasty side-effect for those that purchase food. The price of corn, for instance, used in a LOT of food items.
With the EPA now trying to force 15% ethanol fuels into pumps, things may get nastier.
The worst part of ethanol use, at, say, 8-10%, which is very common, is for 2-stroke engines. BAD BAD NEWS, particularly for pre-mix engines.
I am running a '76 R75/6 and have a reliable source for non-ethanol regular grade gas. Is there a commercially available (NAPA store or PEP Boys) additive that I should be buying to go with that? If so, what and how much do you add?
Welcome, Bob! Glad to have you here...look forward to more inputs. Most know of your website, which is a reference here from time to time.
Thanks for the Welcome!
I seldom get onto the MOA tech site very often. Frankly, I'm not much for the forum system, which has too many categories to follow at the same time.....unless something has changed about that. I do monitor and participate on the IBMWR.org tech mailing list; and my biggest involvement is with the Airheads LIST (from Micapeak.com). I also participate on the Yahoo Groups sidecar list (SCT2) and Kbmw list.
I'll try to "drop-in" more often here.
BTW...I don't know of any NON-T.E.L. additive that works as well as TEL for the old valve seats. FWIW, I'm still using a wee bit of TEL in my fuel for my ancient snowblower (1969 model!!!). It gets used heavily in Winter, and have never had the head off. For those who are going to convert to what is typically called "unleaded" valve seats (1985+ BMW seats, for example), I recommend a real specialist, with real experience on BMW heads. It is tricky to do the job properly....you need the right interference clearance (usually 0.005"), and need to heat the head quite hot (near 500 degrees). Probably very few unconverted seats out there nowadays....still run into them now and then. Top ends on Airheads work very hard, and a proper top end, with correct seats and valve guides (I do NOT use BMW guides) is necessary.
Bob, aka Snowbum
Not to high jack this too much, but I've been on the micapeak Airlist for more years than I've been here. I like both setups for different reasons. One "problem" I have with the Airlist is that I get the digest and am now only reading emails from last Christmas! Yikes!! Needless to say, I can't be part of those conversations since I'm so far behind everyone. But I vow to read them all!!
If you need any help with the set up here, let me or one of the moderators know and we'll do what we can.
Thank you, Bob aka Snowbum for sharing your vast knowledge with us!
My question is pertaining to "Octane Supreme 130". Has anyone used this stuff & is it what it claims to be?
T. Waits.."Got to get behind the mule.. in the mornin and plow"