This is a 1997 BMW F650ST, also known as a Funduro. A client had just bought it and brought it in to be made roadworthy again. It had been sitting parked for a few years...and had a few problems...most of which the seller did not disclose. Some were obvious (like, it wouldn't start!). Some only became apparent after it was running again.
Once the carbs were cleaned, rebuilt and re-installed, the bike got new spark plugs and fresh gas and then fired instantly, (Yay!) Unfortunately, there are some things that just cannot be known until the engine starts running and test rides get underway.
THE NEWLY OBVIOUS
The radiator went to a repair shop, which fixed it successfully...full flow, no leaks. Then the thermal switch that controlled the fan was proven dead and was replaced. The radiator cap was replaced just for good measure, a step that was way overdue. The upshot? No more overheating!
The battery was still running down. Some quick testing showed that the alternator was producing 3 phase AC voltage (> 50 VAC per phase at 3k RPM), just like it should, when it was unplugged from the rectifier / regulator assembly...and was not when the regulator was plugged in...and the regulator was not producing charging voltage (~14V DC) when the bike was running. So...a clear case of bad regulator. In addition, in the course of troubleshooting the electrical problems, we discovered a couple of spots in the wiring harness (between the alternator and the regulator) that had gotten so hot at some point years ago that insulation was burned off. It was pretty plain that connectors had become corroded and gone ohmic (partially open), resulting in overheated connectors that burned the wires. The bad connectors were cut out of the wiring harness and replaced. We tried a cheap knock-off regulator, but it too failed within minutes of installation. A couple of days later we had a genuine BMW unit installed and the charging system was cured. Like magic, the bike produced 14.4 VDC to the battery @ 3k RPM. Perfect.
The previous cursory inspection of the engine oil drain plug had revealed it had been installed with no crush washer, so a leak was no shock. But when a new crush washer failed to stop the drips, it was clear that a closer look was needed...and the sight was appalling. The drain had been manhandled by a neanderthal on multiple occasions. For starters, at some point, someone had screwed the plug in so tight that they cracked to block. (Note: This bike uses a "dry sump" oil circulation system, meaning, it does not have an oil pan on the bottom of the engine. Instead, oil is scavenged off the bottom of the crankcase and pumped into an oil storage tank, from which it is pumped back into the engine. The design is better for off-road bikes that would go into oil starvation if oil were splashing around in a big oil pan when the bike was bouncing around off-road. So...the engine oil drain plug is screwed into the block itself...not into a replaceable oil pan. ) So...yikes!
The good news turned out to be that the crack had previously been repaired. Somebody drilled out the case and installed an insert that was tapped for a new plug, which effectively sealed the crack. The bad news was that some other moron had since over-tightened the plug again (without a crush washer) and had chewed chunks out of the mating surface where the washer was supposed to land. There was no way it would ever seal. Well, desperate situations call for desperate measures. Judicious application of fine grit wet/dry sandpaper and a flat sanding block whittled the drain hole outer surface down to flat...at least flat enough for the sealing washer to fill any gaps. It worked. No more drips.
There were just a few more items to cover.
The broken analog clock in the dashboard would have cost a king's ransom to replace. It fits into a standard 2" round meter hole, so swapping in a standard 2 inch $20 DCV panel meter, which is infinitely more useful, was a no-brainer. And the power outlet and phone mount went onto the handlebars with minimal fuss.
The outcome? See for yourself. Looks like a pretty happy customer to me.
I emailed Dave and quickly had a diagnostic appointment in which we talked through some basic troubleshooting and came up with a plan of attack. Dave emailed me over the weekend to let me know he couldn't resist poking around a little, had identified what we needed to work on, and gave me a short list of specific parts to buy (and exactly where to buy them) before our work appointment.
It turns out my issue was largely due to missed maintenance, but Dave took time to explain both how to fix the issue I'd created and take proper steps to avoid it in the future. In addition to best practice maintenance (oil change, cleaning filter, gas storage), I also learned some "basics 2.0" items like spark plug gap spacing, applying the recommended torque when installing a new plug, troubleshooting and draining a carburetor, etc.
Not only do I feel a lot more informed and empowered to tackle engine issues in the future, I had a blast hanging out with Dave and learning from him. In addition to being an expert, he's a super easy-going guy and a gifted instructor.
I'm lucky to live near WrenchMonster, but it's worth the drive even if you don't. Don't hesitate to reach out to Dave on any engine issues big or small.
- Wyn Gregory
(Yes, the post title is a dad pun....for which Wyn bears no responsibility. - ed.)