BMW R1100 S
Ralph Ferrand with the Boxer.
Iam back at the bedside of the R1100S, which is in serious need of somewhat more than a facelift after enduring 160,000 miles under the cruel whip of a giant Scotsman with a serious addiction for speed.
With the owner clad in Rukka riding gear, the poor machine got no time off, even when schools are closed for the cruel extremes of British winters. While the machine has barely missed a beat during a lifetime of the sort of abuse that would surely kill a lesser machine, this one truly needs its wounds to be healed and I am the man daft enough to take on what is a virtually impossible job. This month I am beset with what has become a very familiar litany of obstacles in my quest to disassemble the Teutonic twin before it can have all its injuries dressed and vital organs returned to good health.
I kick off by pulling down the two top-ends, which on most bikes isn’t a biggie. Removing the rocker covers was no
massive deal as they have doubtless been removed regularly at service intervals to check the valve clearances on the rockers.
I made the unwise assumption that taking the insides of the engine apart would be child’s play as it was all running in oil. Many of the fasteners were either done up by a German with muscles like Popeye or a powerful impact wrench. The Bavarian boys also seem to have a liking for Loctite with a grip like a Yorkshireman with his wallet.
The cams run in the head below the rocker gear driven by chains from the crankshaft. There are followers that are pushed in and out by the cam lobes, which in turn push the single end of the rockers. The rockers have two arms the other side with adjusters that push the valves open. The head has two inlet and two exhaust valves.
Whilst I do have the full factory manual, it is the antithesis of verbosity: it uses one short sentence when in actual fact a goodly sized paragraph would be advantageous in the extreme (Ralph, have you ever gone through your and Steve Cooper’s copy? Bertie...). Their view is clearly that less is more when imparting information, which I found frustrating. One problem that occurred was that when it came to remove the cam sprocket, it would have been good to be able to lock the engine up and that would ideally have been achieved with factory tool 11-5-640, which locks the teeth of the starter ring on the flywheel. Not only did I not have this, but I could find no one breaking their neck to supply me one and, as gearbox and clutch were still fitted, I machined up my own version of a special tool to fit at the other end of the crankshaft as an alternative. After the cam sprocket cover had been evicted, I fitted a suitable hex driver into the cap screw holding the right-hand cam sprocket to the cam. I then fitted a breaker bar to the hex driver and applied what seemed a lot of pressure to release the bolt, but it wasn’t moving. I read and re-read the instruction in the
BMW factory manual, which I quote verbatim: ‘Remove/pull off cam-shaft sprocket.’ It didn’t mention any highstrength Loctite bond that needed to be broken or any left-hand threads or anything. I decided to warm it up with my heat gun and use a long half-inch drive breaker bar to increase the mechanical advantage. And still it would not shift. I moved around to the other side and that was the same story.
Bugger. As I was unfamiliar with this part of the job I decided that more research was required; perhaps the Germans thought it would be amusing
not to mention a left-hand thread? I messaged a friend working at a BMW main agent Down Under and whilst he wasn’t overly familiar with the model himself, was pretty sure that were it a left-hand thread, the manual would say so. I then googled the problem and discovered that these bolts were often as tight as a duck’s arse and that the only way to shift them was the application of heat, and plenty of it. Given the cam-chain guides are plastic I wasn’t keen to go OTT with heat, so tried the big air impact wrench. That wouldn’t touch it, but did shear off the dowel pin on my crankshaft locking device. I made a new pin from silver steel and accepted that lots of heat was clearly the only way to go. I fired up the propane torch and progressively heated the bolt up, intermittently applying lots of torque with my Aircat air impact gun. The right-hand one finally gave in and came out. The left one had the same amount of heat applied, which was monitored with the infrared thermometer, but that one wouldn’t shift until the bloody bolt was glowing red hot! Suffice it to say, all the plastic cam chain guides were burned to a crisp and I wouldn’t use the chains again either. I do wonder what effect the heat treat would have on the sprockets themselves. It was ridiculous that I had to use so much torque and heat to disassemble such a component and were this not a major stripdown in the first place, the damage caused by the removal of these bolts would have led to it anyway. The only saving grace was that the bolts were of the highest quality and seriously hard; were they not hardened high tensile then they would surely have snapped off or rounded out, causing even more wailing and gnashing of teeth. I have no idea why the Berlin (or Munich boys as Bertie seems to insist on me saying) used such extreme thread lock; they may as well have welded the things in place.
The end of the crankshaft needed some dressing afterwards as my locking tool with silver steel dowel had so much torque transmitted through the cam chains that the dowel deformed, as did the hole in the crankshaft, as can be seen in Photos 11 and 12.
The remains components of the rocker gear were easily disassembled and then the bearing caps for the cams removed, taking into account the markings showing which way round they fit. The cams came out with no further difficulty. Once out though, they had deep, eroded craters in them, the like of which I have never seen before, so they were consigned to the scrap metal bin. My customer researched this strange phenomena and discovered that it was not unheard of with this component. What I find strange is that the bike was running fine when stripped.
Removing the cam-chain tensioner caused no major headache and the majority of the bolts securing the heads were removed without grief. The M6 cap screws on the outside naturally put up a fight, having been subject to corrosion. I fitted a long series hex driver in each head and gave it a sharp tap with a copperfaced hammer and a warm-up with the propane torch. The heads came away to reveal 160,000 miles of carbon on the valves, combustion chambers and piston crowns, but nothing really bad.
I undid and removed the screws in the barrels holding what was left of the plastic cam-chain tensioner blades. A few more caps screws were removed and the barrels slid off the studs. On most bikes I have worked on, the gudgeon pin circlips are fitted in a groove inside the piston casting in the skirt, but modern pistons like these don’t really have any skirt in line with the gudgeon pin, presumably to reduce piston mass. The gudgeon pins have grooves in them and the circlips are attached to the pins, as can be seen in Photo 19 where I am removing said clip with circlip pliers. I firstly removed the right-hand piston from its con-rod by removing its gudgeon pin, which gave me the clearance to undo the big end bolts for the left-hand con-rod so that I could remove its piston and con-rod in one. I then removed the other con-rod in the same manner from the other side.
After fighting this German engine apart, I was properly ready for some English Hobgoblin Ruby ale before any more laying on of impact wrenches and propane torches and profane language!