Sunday, April 17, 2011

Breaking a Beemer Boxer Myth

Yesterday I adjusted the valves on the Beemer and I'd like to break a myth about servicing BMW boxer engines. One of the reasons that some people speak poorly about BMW's is because they require servicing every 6,000 miles.  This is true of any horizontally opposed engine with mechanical valves such as the original style VW Bugs and Porsches. The reality is it's not only a fairly simple task, it's also very satisfying.  Allow me to explain but first a little background.

Many moons ago when I met Amber she had a '67 Bug and I had a '61 356 Porsche convertible.  Every time I'm reminded about that car I feel like... ah, crying because it sure would be nice to have now.  Shortly before we got married the Porsche had a valve burn out because it was adjusted too tight.  At the time I didn't know anything about working on cars so I took it to the same independent shop that I use to take my '63 VW Bus for servicing.  The problem was the shop wasn't real experience at working on Porsches.  We didn't have the money to get the Porsche fixed and working on it myself was way too scary.  It was something only professionals should do, or so I thought.

About a week before our wedding I had the Dunlop radials taken off the Porsche and put on Amber's Bug.  That was probably a bad move because the night before our wedding we left her Bug parked outside our future apartment and it got stolen.  The car was later found but had been converted into a dune buggy.

About three years later we bought a beautiful light blue '68 Bug for $800.  After about a year the motor needed rebuilding and my independent shop wanted $700 to do the job.  Not long before this we had bought our first house and our first daughter was an infant.  We were strapped for money and spending $700 was out of the question.

That's when Amber coaxed me into rebuilding the motor myself.  At first I was reluctant because it seemed like a huge mountain to climb with me not having any experience.  I bought John Muir's book "How to Keep Your Volkswagen Alive."  If you haven't seen this book it's worth a look if you can find one.  It's both informative and funny.  By the mid 70's VW Bugs were everywhere and this book was popular. Now it's a classic.  Like it says, it's for the complete idiot.  It walks a person through every step including when to take a break and when to have a beer.

It was because of this book I was able to rebuild that motor.  It was my first and consequently a hugely rewarding experience.  It opened my eyes in so many ways as to how a motor works.  I felt I knew that car inside and out.  The result was a far more gratifying driving experience. The myth was broken that only professionals can work on cars.

Now I'd like to break that myth for you on how difficult Beemer boxer engines are to service.  Let's look inside.

Without going into a lot of boring detail let me just say that each cylinder has two sets of valves which consist of two intake and two exhaust.  The goal in doing a valve adjust is to insure that when each set opens they open to a prescribed amount.  Let's get on with the work and hopefully this will make more sense.

The photo above shows the intake valves on the throttle side.  They're hidden inside the two springs.  We'll look at the adjusters in a minute.  Look below the lower valve spring and you'll partially see a chain.  This is the timing chain and has two markers on its gear that tell us when each piston is at "Top Dead Center" (TDC).  We want the the piston in the ready-to-fire position at the upper most point (TDC).  That way there will be lash or looseness between the end of the valves and the rocker arm adjusting nuts.  In a position other than TDC those springs would be compressed and that would be a bad time to set the adjustment.  The rectangular block barely visible to the left of the chain is our marker that tells us the piston on the clutch side of the bike is at TDC.  I put the bike in 6th gear and bumped the back wheel with my hand in the direction it normally goes to get this marker in its position.

The good news was both sets of valves on the clutch side of the motor were still within the correct tolerances and didn't need adjusting.  See how easy that was!  We're halfway done already! 

The photo above shows the throttle side of the bike.  I have already bumped the rear wheel so the marker for this side is in its proper spot at TDC.  This side is where our photos will come from.  I've stuck the four feeler gauges in their respective spots to show where all the action happens.  The exhaust valves are on the right and are adjusted to .30 mm clearance while the intakes on the left and will be set to .15 mm.

There is more to this but I don't want to risk your eyes glazing over and you dozing off at your computer. If your laptop isn't plugged in your battery will wear out and you'll wake up to a black screen.  No, I've never done that.  Although this might make a handy sleep-aid in the future so feel free to use it that way if you desire.  There won't be any copyright infringement.

Here's where things get kind of busy.  There are three things going on.  We're sliding the feeler gauge up and down to feel the drag between the valve end and the adjuster.  We're controlling the drag on the feeler gauge with the hex wrench in the left hand.  And we're tightening the adjuster nut with the 10 mm wrench in the right hand once we get to the correct drag.  This is done in concert. The key is to get both valves set to the same drag so they're as close to identical as possible.  This makes for a smooth running bike with a smooth idle.  This is the hardest part of the process but trust me, after you do this a few times you become experienced quickly.  It's a simple trial and error process that's fairly easy after you get the hang of it.

This is repeated on the intake valves but using the .15 mm feeler gauges.  Once we get these two sets adjusted we're done.  You now have the satisfaction of doing the job yourself, spending the afternoon bonding with and learning more about your bike, having the assurance that it's done properly, and saving a fair amount of cash.   BMW club members have a wealth of information available on the forum online for doing all kinds of work.  So if 6,000 mile services are keeping you from owning and enjoying a BMW Airhead, I'd like to expel that myth.

No matter what brand of motorcycle you ride, if you haven't done your own work don't let the fear of the unknown stop you.  I recommend getting a manual, doing the research, investing in some tools, and enjoying the extra part of owning and riding a motorcycle.

I also changed the oil and filter and want to mention that I had a helper.  Our 5 year old granddaughter, Avery, was handing me tools and was the person behind the camera on some shots.  She said she might ride on the Beemer someday and that maybe it will be when she's eighteen.  I told her I hope it's sooner than that!  She brought me the handful of dandelions.

When the work is done and there aren't any leftover parts, that's a good thing. The only thing left is to wash the bike and go for test ride.

I can't think of another machine that gives the owner the reward of actually feeling and hearing the results of a tune-up like a motorcycle.  Because we're straddling the motor and holding the handle bars we can sense when things are a little off or spot on.  Doing your own work gives you an even greater awareness of how your machine is running.

It's been almost two years since I got the Beemer.  She's due to have the brake system flushed so stay tuned for that job in the coming weeks.

God's speed.


  1. We have that VW book. Our son went through a VW phase, and at one point we had a couple of buses, a couple of squarebacks, and the requisite parts vehicles to go along. If Ron finds out BMW's bear some relation to VW's he may never go near one! :)

    Of course you have to do three things at once. You have two hands. If you had three hands they'd design it to have four things to do at once. (Kari's guide to R&D). Nice write up on the valve adjustment. It scares me how much of it I understood.

    Dandelions from the granddaughter--best bouquet ever.
    Have a great week Mike! :-)

  2. You should also check and adjust if necessary the rocker shaft end float clearances. I have started servicing my R1150GS myself and tightening this up to minimum clearance has made the engine sound and run a whole lot better! Official BMW workshops over here in UK do not seem to bother with this.

  3. Too bad about not keeping the 356, things are much more obvious in hindsight. I think I still have that VW book. I had picked up a couple of buses and they came with a lot of extra parts and books. Sold the whole project a couple of years later.

  4. Kari,
    That's funny about doing more things than the number of hands. I've never looked at it that way but it's true. VW buses are worth a lot of money these days if they're older. It sounds like Ron doesn't like VW's though. Have a great week Kari, thank you!

    Thank you for stopping by. You are absolutely right. I was going to include the rocker arm end play adjustment, I even took a photo but decided not to include it because it can be complicated to make that adjustment. Fortunately the rocker arms hadn't moved since my last adjustment.

    When I first bought the bike I took it to an independent shop to have him go over it completely. The first time I adjusted the valves I felt the rocker arms were too tight so I loosened them. I got them too loose and wow was it noticable. A lot of vibration and a deep knock when accelerating uphill. I called the shop and was told they don't take the time to measure them and just bang them up tight with a hammer and call it good. I learned through the trial and error process on those too. You're right the shops don't fool with these but they make a difference. Thanks again!

    Wouldn't it be nice to keep all the vehicles we've ever had? Maybe not, my wife wouldn't allow that. :-) In some ways a motorcycle fills the sports car thing. They're sporty and fun. I do think a bus would be fun to tinker on though. Thank you!

  5. Mike:

    OH Man, the 356 roadster was my dream car. I used to have a '59 bug and everytime I went to the dealer I went into the showroom to stare at the "bathtub" . I've had a couple of bugs, and even a Westfalia and a Rabbit Cabriolet.

    I'm waiting for your tutorial on your spline lube. I'd get a beemer in a flash if you were my next door neighbour

    Riding the Wet Coast

  6. A very nice write-up on breaking the "BMWs are hard to service" myth. Next, we'll see you doing the ABS system and brake circuits I assume?

    I will comment on the aspersions the non-cognoscenti casts upon the 6000 mile requirement of Beemers with Boxer's not that often or low a mileage interval, they should try the 3000 KM service interval of a Ural!

    The thing that was most vexing to me when I first started doing my own valve clearance checks, was quantifying the "slight drag" once should feel when one thinks he's got the clearances correct. The moment of enlightment came with the realization that once you have it "right", you should not be able to slip in the next size up feeler more deciding whether the slight drag was correct. : )


    Redleg's Rides

    Colorado Motorcycle Travel Examiner

  7. Bob,
    You've had some nice cars... including your current Vette! A '59 bug would also be a nice project car these days especially with a rag top. Thank you for your kind words. That would be nice to have you as a neighbor! And to ride together! And I could learn more about photography from you!

    On the spline lube if you're referring to the spline on the final drive I did that last year but didn't post it. I should be doing it again in the summer sometime. I think I might start posting the work I do to show how non-threatening it is. Thank you!

    Thank you! Yes, I plan to tackle the brake fluid replacement next.

    Wow, the Ural folks are pretty tight on the service intervals! I guess that's good to stay on top of things though. I forgot to make that point about BMW's. For the folks who aren't riding all year it's not that bad.

    I agree, learning the feel of the drag is a little daunting at first. As you said, it's hard to quantify. I've come to the point of having a tight feel with a steady resistance. I've found this cuts down on the clickety-clack noise under the valve covers at idle and also makes for a smoother ride. Thanks Dom!

  8. kuddos to you for DIY!!! I'm a auto mechanic and work with six other mechanics that ride and guess who fixes their bikes, ME. So many folks are scared to understand how things work and how to fix stuff.

    Thank you for stopping by! That's funny that the other guys don't work on their bikes. I use to be a tool distributor so I know that some mechanics don't want to work on anything when they're off work. Hope you have time to ride after working on all the bikes!

  10. That's one good thing about the bimmer,easy to get to the valves, on the Kawasaki Concours, the side fairings have to come out, the tank has to come out and then it's a pain to get the valve cover off from the frame :-(
    I have been telling my brother to do the same to his GS1200A but he is afraid to touch it while it's under warranty.

  11. George,
    Well it's fairly easy on the RT's to get to the valves. All of the "tupperware"/fairings have to be removed which only takes about 20 minutes. Then it's a naked bike like the GS's. The Connie sounds more involved, especially taking the tank off.

    Your brother has a good point about not working on it under warranty. I think BMW is pretty strict about having reputable shops do the service work while under warranty and logging it into the computer and service book. I bought my bike used and just out of warranty. But if he intends on keeping it and can handle anything that goes wrong he should start working on it now - IMHO. :-)

    Thanks George!

  12. Look at you. There's more to you than meets the eye. Like peeling back the layers of an onion. I'm all for practicing valve adjustments. Just on somebody else's bike!

  13. Irondad,
    LOL... That's funny! On your bike though, you don't have to worry about valve adjustments but every 60,000 miles, right?