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Tech Q&A: Identical bikes and aching knees


I have two identical bikes. One K 1200 S runs great, but my backup K 1200 S from the same year is hard to start and doesn’t want to stay running. It’s worse when the bike is cold, but even when it’s fully warmed up, it will still try to stall out. Why don’t these bikes behave the same and what can I do about the one that doesn’t run right? I keep up with regular service, so I’m at a loss about why they act differently. –Preston T.


My wife (who loves me) has an identical twin sister that barely tolerates me. Your bikes are not identical.

Like my wife and her sister, your bikes have different life experiences that have brought them to this point. The transversely-mounted K 1200 engines (i.e. Japanese style inline 4) are prone to warping air box issues, which could be the reason you gave one of them backup status in the first place. A warped air box causes high idle, degrades acceleration, makes the bike hard to start, and can cause other running issues. Even if you bought a first-year K 1200 S, you’d need a final year K 1300 S airbox, which seems to be the best solution for these air box issues.

Knowing that this bike sits more than its sister, I have to wonder how much does it sit? BMW wants your bike ridden at least 100 miles a month, which they believe will stave off a lot of these kinds of problems. If you’re not riding it that month, you might suffer from excessive moisture in the gas tank, stratification (separation) of the fuel, gummed up fuel injectors, or deteriorated components inside the fuel tank (fuel filter, fuel lines, etc.). These are all common issues that crop up when E10 gas sits for a long time.

Start with a common fuel treatment such as Sta-Bil, Star Tron, or BMW’s fuel treatment solution and a fresh tank of high-quality gasoline. Follow that up with more fuel treatment and more fresh gasoline—in other words, Ride, Fuel, Repeat. If after three full tanks in a month, the problems persist, you’re probably looking at a mechanical issue rather than a chemical one. You may need to replace some or all of the fuel tank’s internal components, fuel lines and/or injectors. Worst case, your airbox may suffer from the warping issue and need replacing. (GM)


I’m almost 50 and my knees are killing me on long rides with my 1999 K 1200 RS. I love the bike and there’s nothing wrong with it, I’ve had it for eight years, but I’m considering turning it into an F 800 ST. Are you familiar with the seating positions of the two? Will I run into the same knee trouble with the F bike? –John S. via Facebook



I ride a 1998 K 1200 RS, so the ergonomics are going to be identical to your 1999 K 1200 RS. I’ve ridden several F 800 STs, one of them for a couple of thousand miles. I’m also only a couple of years younger than you!

I believe you will find the ergonomics between the bikes to be quite similar. They are not identical, but they both have knee-aggressive footpeg locations and similar, though not identical seat-to-handlebar reach lengths.

If you want to hang on to your K a bit longer, one thing to look at is a footpeg lowering kit. Pirate’s Lair sells one made by Verholen; it’s not cheap, but the quality is outstanding. They also sell a set of wider footpegs that the manufacturer (a British company) claims adds long-distance comfort. It’s likely that between these two things, you may find some ease for your knees. Buying both kits will set you back over $400, but that’s a lot cheaper than a new bike. Make sure your kit includes both the footpeg plates and the shift lever extension (see the photo and pardon the rusty bolt!).

Given my experience with the F 800 ST, which is a fantastic bike on its own (if a little buzzy at high speeds), you won’t find any relief in the knee angles there without modifications similar to what I’m suggesting with your K bike. If you decide to go that route, check out the kit offered by Suburban Machinery for the F series bikes. (WF)

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