[ ad supports Snowbum's website ]
Disassembly & Assembly of cylinder heads for BMW Airhead Motorcycles.
Pistons & piston rings. Cylinders. Damaged cylinder stud threads at the engine case.
Helicoils & Timeserts. Intake stub spigots.
© Copyright, 2017, R. Fleischer
Article 60, section 1
If you are installing a camshaft and/or followers, READ http://bmwmotorcycletech.info/cams.htm regarding assembly pre-lubrication.
You may think that pulling off a jug is major surgery & frightening to contemplate. Once you do it, perhaps at a TechDay; or, from the information in this article, you should no longer have much apprehension about doing it yourself.
CAUTION-1: Every year comes questions about removing a head, perhaps for a simple de-coking (and not pushrod tube seals), & whether it is possible or not....to keep the cylinder sealed at the bottom. In order to do this, you would have to very securely wrap bungees ...or via some other means, ...around the cylinder fins, across the motor, & all-around the motor. Or some such. You would have to keep the cylinders from moving off the base area in the slightest. This method has been done when I only needed to work on the heads & was being done 'in the field', such as at a Rally, or a TechDay, & no O-rings and no piston ring compressor were on hand, etc. But, in order to do it, the bungees must be super-tight & evenly surrounding the cylinder, fore & aft. I recommend you not try it. Chances are high that you will not be fully successful & your cylinders will leak oil.
CAUTION-2: Never reuse a head gasket unless it is a real emergency. While it is possible to leave the two head-to-barrel nuts in place (the ones located at 12:00 and 6:00), & to reuse the gasket by never separating the head from the barrel, this is a poor idea. It MIGHT result in distortion of the assembly. I have not seen that distortion, if the assembly is done fairly quickly, within minutes. Pure speculation anyway. These 2 head nuts (located at 12:00 & 6:00) are supposed to be the first to be loosened, the last to be tightened (in the usual cross-staging).
Sandblasting, or other media blasting:
I don't like the finish that soda blasting leaves & soda must be 100.00% removed, or it starts its own chemical reactions. Walnut shells are OK. Carbon Dioxide (CO2) is OK. Sand & glass bead blasting, usually just called Sand Blasting, are not ok (leaves hard particles imbedded in the aluminum, which can come out & raise hell with the engine innards!) ...with possibly an exception ....the form of blasting called wet blasting or slurry blasting. This can be OK to excellent, and leaves a nice finish. Vapor Blasting, as it is usually called, is generally safe. This type of cleaning is not new, it has been done since WWII for aircraft. Very fine particle abrasives are used, with lots of water. While the major benefit is that dust is kept well under control (a BIG advantage for small to moderate shops), it is also true that the very fine media in water does not lend itself to embedding hard particles in the aluminum alloy parts being cleaned. The water essentially flushes away the particles.
This remainder of this article is only available for Airheads Beemer Club members. Please Log In..or..Click Here to join the Airheads Beemer Club, after which you will enjoy access this article and all members only content of the ABC web site.
© Copyright, 2017, R. Fleischer