Common Mistakes
In this section...
______Oilhead Cam Sprocket Removal ______
When removing the heads of an Oilhead motor, it is very important to refrain from using an air impact wrench on the
cam sprocket bolt which can cause damage to the chain tensioner rail. Normally it is required to split the cases to
replace any of the chain rails other than the right bottom rail which is held in with a bolt accessible from the rear of the
engine. However, Dan Barnett was kind enough to share this photo of the left upper chain rail replacement. Dan found
that by breaking the corner of an oil baffle inside the block, there is enough clearance to replace the chain rail.
Photo courtesty of Dan Barnett.
Thanks for the info Dan.
We also strongly recommend upgrading the left tensioner piston to the new style with check valve introduced in mid
production 2005 R1200GS models (fits all older Oilhead models). The old style piston is responsible for the clanking
noise you hear during start up. That noise is your chain tensioner being bashed around by the chain until the oil
pressure builds up. BMW redesigned this piston for a reason. We believe the old style piston is responsible for the high
incidence of broken left chain tensioners. The new style piston has a check valve to prevent oil pressure leak-down
when the engine is shut off. The new style piston can be found in our on-line store under engine mechanical parts.
______Noisy Oilhead Rockers______
We often get Oilhead models in for service with very noisy valve gear. The on-line video technician training from BMW
that covers the valve adjustment for these models specifically states that although the factory spec for rocker arm end
float is very liberal (.05mm-.40mm) it should be adjusted to the minimum end of the spec range to reduce noise, at the
600 mile service while the heads are being torqued. Once the rocker end float is set, it does not need to be adjusted
again. Unfortunately many bikes that come to us for the first time, some after many dealer service visits I might add, still
have very loose rocker end float. Every Oilhead valve adjustment at the BeemerShop includes correct setup of the
rocker arm end float. You might be surprised how much quieter your Oilhead can be after a BeemerShop service visit.
______Thread Repair______
The person that installed this thread repair insert did not install it straight. The fill plug gasket is now squishing out on
one side because the plug is not perpendicular to the threaded hole.
I use custom made tap guide fixtures to ensure that all thread repairs are done with perfect alignment.
______Airhead Head Gaskets______
This head gasket was installed upside down by the previous mechanic. The pushrod holes are partially obscured by the
gasket which commonly results in rub marks on the pushrod. Be careful to find the correct way before installing your
______/2 Slinger Screws______
This customer had an engine noise which was traced to an incorrect slinger screw, (you can see the rub marks on the
face of the screw). Some years ago, slinger screws where not available. Some mechanics were using the seat hinge
screws from the 1970's models. They worked -- sometimes. The problem with them is that they did not sit as low in the
slinger as the original slotted head screw and could come in contact with the back of the front main bearing holder. The
correct screws are currently available again and I discourage the use of the seat pan screws.
______Airhead Rocker Arm Shafts______
The previous mechanic installed the left rocker arm shaft upside down. The resultant oil starvation to the rocker arm
damaged the rocker bearings, shaft and one support block. On the 1970-on Airheads, the top two studs supply oil to
the rocker arms. The rocker shaft with the hole drilled inside must face upwards so that the oil will travel through the
rocker shaft to the rocker bearings.
______Bing Choke Valves______
This R75/5 customer was complaining of poor cold starting. I found his choke valves installed on the wrong carbs. The
choke valve is labeled R for right and L for left. They must be installed on the correct carb, right or left, as you're sitting
on the bike. There is also a dot on the shaft of the valve which must point toward the lever that's installed on the shaft.
______Gear Oil Levels______
When changing the gear oil on an Airhead, it's a good idea to remove the fill plug first, for two reasons. First, if the fill
plug is seized and won't come out, you don't want to find that out after you have drained the oil. Secondly, you can
determine if the oil level has risen which is generally not a good sign. This customer had a leaking final drive input seal.
His final drive oil level was high, and there was little oil in his swingarm. There was extensive damage to his coupling
gear and driveshaft from lack of lubrication. I recommend changing gear oils every 10K miles or once a year, and if
your oil is migrating, replace those seals to prevent further damage.
______Wheel Bearing Service______
This R100/7 customer thought his bike didn't need a wheel bearing service. He was lucky he didn't ruin a wheel hub. In
the 1970's BMW recommended servicing the wheel bearings every 10K miles, the interval was changed to every 20K
miles in 1981, for models up through 1984. However, some folks have no idea when their wheel bearings were
serviced last. If enough time has gone by, even with low mileage, the grease can break down or become contaminated.
If you don't know the service history of the wheel bearings, have them serviced. When they fail it can cost you a wheel,
or worse (in one case a customer bought an axle, a fork leg, a wheel, and a lot of labor). The bearings should be
cleaned, inspected, properly shimmed, lubed and resealed every 20K miles or every 4 or 5 years at the most. The
sealed wheel bearings of the R65LS and the 85-on models are not serviceable and are suppossed to be replaced
every 25K miles. They have proven to be very reliable. Many folks wait until 40K or 50K miles before replacement
(some never replace them but we won't talk about them, you know who you are). I have seen one failure at 29K miles
but that was an exception. If you want to be on the safe side, replace the R65LS and 85-on bearings every 25K miles.
______Backwards Gas Cap______
During a routine service on this K75 I found this gas cap installed backwards (should open toward the rear).
When I removed it I found the gasket installed incorrectly also.
The gasket has a cutout which must be placed over the condensation hole in the gas tank.
When installing the gas cap, the cut-out in the cap assembly and the cut-out in the gasket must be positioned
at 9:00 over the hole in the tank so that moisture that collects under the cap can drain out through the condensation drain.
Cracked Subframe
Early saddlebag mounts for Airhead models did not have a lower support from the bottom of the bag mount to the main
frame next to the passenger footpeg. Without the lower support, the added stress from the weight of the bags would
often crack the subframe.
Old Style Mount
New Style Mount with lower arm
Early style bag mounts should be modified or replaced with the later style mounts.
______Early Airhead Saddlebag Mounts______
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