The Oil Leak

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“You have an oil leak,” my friend Mike remarked last July, looking down at my engine. The bike was on its sidestand, so you could get a good angled view into the skid plate, where a glistening smear foretold almost a year of diagnostic troubleshooting.

I quickly localized it to the front lower portion of the engine. It would drip down the front and collect in the skid plate at the bottom. Seeing the oil wasn’t the problem; determining its source was.

Oil can travel a great distance on a dirty engine. The dirt soaks up the oil and transports it across the bike so that diagnosis is like a shell game. Is it soaking up from the bottom or dripping down from the top? All you’ve got to go on is a blow pattern like a gruesome crime scene.

I decided to approach this like Hercule Poirot.

The suspects:

  • Sump plug sealing washer
  • Crankcase gasket
  • Starter motor O-ring
  • Base gasket

 

Sump plug sealing washer

Following the principle of Occam’s Razor, I started with the simplest explanation. I had just changed the oil and cheated and re-used the sump plug washer, so that was my first guess. You can re-use those copper washers a few times, especially if you braze them between uses, but it’s a crapshoot. Yes, there’s oil up the front of the engine, but like I said above, oil can defy gravity on a dirty engine.

I replaced the washer at the next oil change, but the leak persisted. It wasn’t the sump plug washer.

Crankcase gasket

Someone on a forum said the crankcase on these bikes is prone to leaking. This theory was supported by the fact that the leak only occurs at high revs under pressure. So last autumn, while doing some other maintenance on the bike, I torqued all the crankcase bolts. Lo and behold! A few in the front of the engine were under-torqued. Surely I’d found the source this time.

I hit the highway the following weekend and at my first rest stop I took a look in the skidplate: that familiar smear of liquid gold. It wasn’t the crankcase gasket.

The starter motor O-ring.

This is when things got interesting. The leak seemed to be coming from somewhere under the starter motor. There’s a single O-ring that prevents oil in the crankcase escaping at the interface with the starter. Again, I’d had the starter off for another job and didn’t replace the O-ring, which my shop manual recommends. Since the starter connects with the crankcase, the pressure at high revs could blow the oil past the the O-ring.

I replaced the O-ring, waiting the requisite two weeks for this $5.14 part to arrive from Germany. The leak persisted. I decided to get serious.

The best way to source an oil leak is to clean up the engine, take the bike for a short ride, then look. In theory, you should see a trickle coming from the source. So that’s what I did. When I got home, I took the starter off and this is what I saw.

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Is it coming from the starter, the crankcase, or the base gasket?

I said in theory. There’s definitely a trickle coming from that front corner of the engine, but there’re also drops near the front??? Could it be getting past the O-ring, dripping along the underside of the starter motor, and dropping onto the crankcase?

I was down to two suspects—the starter motor O-ring and the base gasket. I was nervous about torquing the gasket. Maybe it’s not a big deal, but those big, crucial gaskets scare me. Mess that up and over-tighten and you are pulling the engine. And in all my research, I had come across only two instances of a weeping base gasket. I decided to stick to the O-ring theory a little longer before interrogating the big boy.

27037-PX-OPTIMUM-BLACK

I picked up some Optimum Black gasket maker. The packaging said it resists vibration (important on a thumper) and is “one of the most advanced, maximum flex, maximum oil resistant RTV silicone gasket makers available.” I added a smear on the O-ring, let it cure 24 hours, and tried again.

Still no luck. I added a bead around the neck of the starter next to the O-ring. No luck.

I put some Optimum Black in the channel for the O-ring, let it cure, added the O-ring, and added a bead at the neck for good measure. Nyet! I found a slightly bigger O-ring in plumbing and tried that. Nope.

I was beginning to think it wasn’t the O-ring.

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Starter with O-ring and gasket maker

I asked on my bike forum and somebody suggested the oil could be coming from inside the starter. I hadn’t thought of that. There’s an oil seal and bearing inside. If the seal is finished, oil could be getting inside and then dripping out of the starter. If the bearing is worn, it could be causing vibration that is preventing the external O-ring from completely sealing. I had noticed slight pitting on the underside of the starter neck, which supported the theory of a worn bearing.

So the starter came apart. I pulled the old bearing using a valve puller and tapped a new one on, adding a new, greased oil seal. I was hopeful this time. There were a few symptoms supporting this theory, not the least that my bike now has over 90K on it, and with the crank revving at 5K rpm, I’d be surprised if that bearing weren’t worn.

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Starter motor disassembled. Note bearing on the armature. The little wires sticking out of the brushplate assembly is a trick I saw on YouTube to hold the brushes in place for reassembly. It was still a right royal PITA to get it back together!

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Pulling the bearing. I wrapped the armature in a rag to protect the wiring and clamped it in my workmate. Since there isn’t much clearance under the bearing, I had to be creative and use a valve puller. The feet of a bearing puller were too big.

Once all back together, I took Bigby for another short test ride. The bike was still leaking. Now I know why people say fixing an oil leak is hard.

This is when my cursing and ruminating and otherwise surly or downcast behaviour elicits from my wife the question, “Why don’t you take it to a professional mechanic?” Actually, others were beginning to say the same, including a club member. My response: “What can he do that I can’t?” (And yes, it’s almost always a “he.”) And the amount of time spent diagnosing this kind of problem would cost a fortune. It was time to concede the inevitable: I’d have to tighten the base gasket.

Base gasket

The base gasket is Item 4 in the diagram below. Tightening it sounds easy—and probably would be on any other bike—but it isn’t on a BMW. The little M6 bolts on the left side of the bike (Item 3) are nested into cutouts in the corners of the engine block, so accessible only with a torx key. I’d have to buy a set of keys and torque those bolts by hand. They are 10 Nm and I think my feel is getting pretty good, so that was the easy part. I nudged them, that’s all.

diag_y8

The other side has two M10 x 223mm bolts that go all the way through the head, the block, and into the base (see Item 1 above), and they are only accessible beneath the rocker (valve) cover. I’d have to open up my engine.

So off came the plastics, the battery, the airbox, the oil tank, the battery tray, the starter relay, the electrical box cover, the heat shield, the intake manifold, the throttle cable, the spark plug coils, the coils holder and, finally, the valve cover.

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Bigby splayed open to access the valve cover.

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The bolts to be tightened are far right, next to the cams, and partially submerged in oil.

With the rocker cover off, I could now tighten those long bolts. I was nervous about tightening those babies! While the little M6 bolts were only 10 Nm, these were 60. I’d need my big 1/2″ torque wrench. Someone on the forum had suggested I back off the bolts a bit first, just in case they are seized, then retighten. I decided to aim for 62 Nm.

The one at the back went smoothly enough; I got an accurate reading from the wrench so moved on to the crucial front one. I could not get an accurate read with the wrench on this one but I did move it a few times, as much as I dared. My experience told me that I’d better stop there or risk over-tightening if I continued. Sometimes you just can’t trust a torque wrench; you have to trust your gut first. I hoped I’d moved it enough or I’d be taking the top end of the bike off again.

That was the tough part done. I took a break, made a tea, and slowly reassembled the bike.

The test

When I replaced the starter, I added another smear of Optimum Black on it for good measure. I also torqued all the crankcase bolts again, replaced the oil filter and added a smear of gasket to the cover sealing ring, and torqued all the engine mountings. Basically I torqued every bolt on the right side of the bike! Desperate times call for desperate measures.

I was so worried about this test I actually didn’t ride for another whole day. I was out of leads, and if the leak were still there, I’d be at a dead end.

The next day, my wife and I headed off for an afternoon excursion into Ontario. We packed a picnic lunch and headed west along the St. Lawrence River. After about an hour and a half of riding, my wife spotted a church overlooking the river where we could stop. I pulled in, turned off the bike, climbed off, and with God and my wife present for emotional support, I looked into the skid plate.

No oil. I looked under the starter motor. No oil.

I’m not a superstitious man, but I dared not celebrate just yet. I didn’t want to jinx myself. But on the way home I intentionally kept the revs up into the 5K+ range to stress the engine. Once back on the driveway, I looked again: no oil!

Now we did celebrate. We poured two beers and toasted the end of the oil leak. This was one of the hardest jobs I’ve ever done. It took me almost a year off and on to diagnose the problem and over a week of full time work to get to the bottom of it. A big thank you to the guys at The Chain Gang for their help. Bigby is now finally ready for the 2020 season.

The finishing touch is a new custom decal designed by my friend Brian Chu at Brian Chu Design and Illustration, Inc. in Calgary. Thanks, Brian.

650THUMPER 2005A

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Double, Double Toil and Trouble

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People sometimes ask me, “Where did you learn how to fix your bike?” I answer, “I didn’t. I’m still learning.” Being a DIY guy is a never-ending process. But the start is usually the same: an oil change. The first thing I did with my 650GS is change the oil and coolant, and because we live in the YouTube era, I lucked out and found a great how-to video by Kirk of the BMW Motorrad Club of Northern Illinois doing this very service on my exact bike! I love Haynes Manuals, but there’s nothing like seeing someone do it “in person.”

From there, I changed my brake pads. Brakes! you say. Don’t you want to get those done by a professional? I know, there’s an emotional component to brakes, but the fact is, they’re really not that complicated—a disc squeezed between two asbestos-lined pads.  When time came (40K) for valve adjustment, I did a bunch of research and plunged in. Each time I start a job I don’t know where I’m going but I figure it out along the way. As the American poet Theodore Roethke says, “I learn by going where I have to go.” And each time I go, I learn more about my bike.

Sometimes the journey is made longer because you don’t know what the cause of your troubles is. All you’ve got are the symptoms. In those cases, your diagnosis is easily half the work. Now if you are an experienced mechanic, you’ve seen it all and you can make an educated guess and save yourself a lot of time. Or you have a machine that costs the equivalent of my monthly wage and does the diagnosis for you. But if you’re a DIY guy on a budget, and this is the first time you’ve experienced these symptoms, you’ve only got the Fault Finding section of your service manual, the brain hive of a good user forum, and your intuition. Using these three tools in the right combination is the most useful wrench in your toolkit.

So when my bike overheated last fall after a little tip-over in sand, spewing boiling coolant out the overflow reservoir, I packed my bags and stepped out for a new journey, one that would prove to be especially long.

I don’t know how the editors of service manuals order the list of probable causes to certain problems. Do they list them in order of most probable to least, cheapest and simplest to expensive and complicated, or some combination of both? Since I’m on a tight budget, I tipped the scales toward cheapest fix first. Top of my list, then, were things like coolant level low, radiator pressure cap defective, thermostat stuck open or closed. So I started there, specifically with the thermostat. I took it out and tested it, sticking it in a pot of water on the stove with a thermometer. It opened just fine at the temp it was supposed to but didn’t close once the water cooled. Hmm . . . Could this be the problem? So off I went to BMW for a new thermostat. At $65, it’s got to be one of the cheapest parts on this bike, so I was hopeful I’d found the problem.

I put the new thermostat in and rode one block and the temp light came on. Damn!

Next I focused on the fan. Was it running when the bike overheated? I couldn’t remember so I texted my riding buddy. He couldn’t remember hearing it running either. Maybe there’s a problem with my fan, then? I connected it directly to the battery. It worked. Good, I guess. Maybe the sensor that turns on the fan is defective? My neighbours must have been wondering what I was doing with my camping stove out on the driveway beside the bike, but I had taken the sensor out of the engine block and was heating it in a pot of water, as I did with the thermostat on the stove. The fan did not turn on. So off I went to BMW for a new sensor. I was confident I’d found the problem.

I put the new sensor in, started the bike and ran it up to temp. The fan turned on. Great! Then I rode one block and the temp light came on. Damn!

Turns out the sensor works by pressure as well as temperature, so heating it alone would not trip it. On the plus side, the fan was turning on, so I knew that system at least was working properly.

The most recent time the temp light came on I noticed some coolant dripping from the bottom corner of the radiator. I surrendered to what I was dreading and denying: the radiator must be leaking. At $600 for a new one, this brings us to the point in the journey where I decide to stick the bike into winter storage early and avoid the problem, at least until spring.

It’s been a pretty brutal winter here in Montreal. Finally spring came, I bought the new rad, installed it, rode one block and the temp light came on. Damn! Double damn!

I’m not going to say the rad wasn’t broken, because I think it was. It was bent from the tip-over and clearly leaking, or so my wallet says. So my problem is . . . shall we say, multifaceted. I little sleuthing on my favourite forum uncovered that the water pump on my bike tends to go at around 50-60,000 kilometres. My bike now has 63,000. I knew this before buying the rad, but because it’s quite an involved process to get to the pump, and because the rad was leaking, I thought it was a long-shot that the pump would go at the same time as the rad. But go it did. When I finally got the pump apart, which involved taking the clutch cover off, the gear that drives the impeller was stripped.

Believe it or not, I was actually happy to see this, for at least then I knew what the cause of my problem was.

How was I to know that both the radiator and the pump were broken? And the pump issue seems to be unrelated to the tip-over. There’s been an effort on the forum to try to get to the bottom of what’s causing the stripped gears but there doesn’t seem to be any consistency. For some guys, it happens out of the blue with no apparent cause; for others, it’s after a drop. My guess is that the impeller shaft gets worn and starts to wobble. Sometimes this results in the seals leaking, sometimes the gears stripping. At any rate, it seems to be the Achilles heel of this bike. Now I know.

With the bike back together again and all fluids replaced, I rode off and the temp light did not come on. Now I’m ready for another season and my journey can be of the real kind.

I enjoy working on the bike, or any kind of manual work, actually. Okay, sometimes there are frustrations, like when I couldn’t figure out how to get the clutch cover off with the oil return line in the way. But that too is just a matter of knowledge. I struggled for a while, then went on the forum and read that some guys loosen the exhaust manifold bolts just enough to drop the exhaust pipe out of the way. I’m looking forward to the time when I know this bike so well that the troubleshooting part will be a no-brainer and I’ll know the route before starting a job. Until then, patience and persistence are my travelling companions. 20180422_145248