If you ask ten motorcyclists about the perfect bike, you most likely will get eleven or more answers, boiling down all sorts of personal preferences, riding styles, etc. In case you do the clever thing and ask for the best engineered bike from the 1980ies and 90ies, you will most likely end up with the bike featured in this post or one of its variants. But let's take a step back, I currently have four very interesting and characterful vehicles on the road. There's the Suzuki SJ410 as a "sort of car". Probably better described as an off-road going motorcycle with four wheels and a roof. Small, versatile, utilitarian, but not exactly what you want, if you have to take a longer trip on the Autobahn. Obviously there's the TR1, which oozes character out of every pore and has been pretty reliable, but has proven itself to not be perfectly thermally stable on the Autobahn. (Though I plan to tackle this issue with a different set of needles that will juice up the midrange, where it is currently running too lean and this might sort that issue out.) Last but not least there's the Dre-XT-Stück, my XT600 bastard, which is a brilliant big thumper and meant to take off a bit of the daily driving work from the TR1 and when it's not broken, it's utterly sh*te on the Autobahn. So to cut a long story short, there's a distinct need for a daily driver, stupidly reliable and very Autobahn-capable.
I present to you, most likely the world's most boring motorcycle. A motorcycle built aiming for two-wheeled perfection and getting so close, it almost lost any kind of genuine character. A bland motorcycle. A perfectly adequate motorcycle. A BMW K75 Basic.
It was undoubtedly an interesting purchase: 77,000km, less than a thousand Euros, not running and the last owner stole lots and lots of parts off it for his other flying bricks. Not exactly the worst starting point, if you're willing to gamble a little.
That is until someone is absolutely insisting on showing you that it will come to live a bit with a squirt of brake cleaner and you don't say stop at the right time. The result: burnt loom, air-filter and airbox. Annoying, but it was at least partially my fault for misjudging the guy's skills the way I did.
Back to the assessment. Coolant is old an bluish-green, but no trace of oil in there.
The engine layout still fascinates me. Just a regular engine, flipped on its side.
Sight glass, where you'd normally expect a drain-plug.
There are multiple reasons, why I am sure the previous guy wanted to break the BMW down and sell it in parts. Firstly, because he openly admitted taking some bits off and secondly, because there were a lot of broken bolts. So I started with fixing numerous castle nuts around the bike and ironically this resulted in the BMW being the first bike that would have pannier mounts installed before even remotely making the first sounds.
Swapping the fuel pump and filter was pretty easy, especially when you buy a complete kit. Otherwise take note that the fuel hose you plan to use, is rated for in-tank-use. BMW dealers will be able to sell you a length of this special hose, part no. 16121180040 . (You can also get it online, e.g. COHLINE 2190 or Stahlbus SB-3200111 NBR/NBR, but the prices will ALWAYS be painfully high, compared to normal fuel lines.)
The oildrain? Not so much. The oil and definitely slightly watered down from some of the previous attempts to get the bike to start, but had no metal bits in it.
But there was an original BMW oilfilter installed.
At roughly this time, my new (used) wiring loom arrived. For anyone, who has to do the same thing: There's an early loom up to 1989 and from 1989 onwards, there's a newer model, which undoubtedly has some improvements, but it also means, you will have the pleasure of swapping out "a few" bits. (Also note, there's a lot of variants regarding whether the donor came with ABS or not and a catalytic converter or not. Luckily for me, most government use K75s were ordered as base models with a fairing and hardly any or no provisions for additional equipment.)
The easiest indicator for the 1989 to -95 loom is the black connector for the instrument cluster (with square pins).
Whereas the older loom has got two white connectors under a cover (already removed in the picture) and as should be very visible, with round pins.
The later square/rectangular pins. Also instead of a self-tapper, it's regular metric screw that holds on the connector.
One of the very few spots, where you can mix things up are those two blue relays: One's for the fuel pump other for the horn. (They are identical, so this might come in handy for someone troubleshooting a non-starting bike...) The big white box right below is the temperature controller for the EFI and is probably one of those things that might be worth having a spare. The black 4-prong connector is for "accessories" and is meant for plugging in your siren and radio gear etc. This loom came from a slightly higher spec bike, so it came with the subloom for a 12V outlet already wired in.
Given the amount of electronics stuffed into the confines of a motorcycle, it was undoubtedly a tedious job pulling out the old loom and installing the new one, but as pretty much all the plugs only have one other counterpart, the most important bit is to install the new loom exactly where the old one went.
Most annoying bit probably were the cables going to the coils as all of them had some substantial corrosion on them, making the old ones rather difficult to remove.
The (unexpected) downside of said little fire was that all the cables (choke, clutch, throttle) seized and this was for once, where all those built-to-order options reared its ugly head. Turns out, mine came with the high bars as normally found on RT models, meaning I needed the "long" cables.
Choke lever is fairly normal, for the clutch cable (especially, when it's seized and you can't undo the tension) a wedge between swingarm and lever on the gearbox will work wonders.
Geared throttle with a tiny chain - only seen this on Soviet sidecars before. The line's a timing mark. Clever. It's the sort of engineering the really makes me warm up to the BMW.
Front brake master was as dead as a door nail. There's a ready made repair kit from BMW/Magura, only thing to know is that you will need a pair of snap ring pliers and the washer will most likely be rusted onto it.
Plenty of brake-lube will hopefully prevent the washer from rusting onto the case like last time.
On early K75 models, both brake switches are identical, as is the one for the choke warning light and for the clutch switch.
One of the other few things that changed with the newer loom, was the connector(s) for the alternator. Swapping it, is pure joy though. (It can be made ever so slightly easier by "gluing" the rubbers in place with some vaseline.
What followed next was to swap out ALL fuel hoses, either they were hard, cracked or too short and instead of the rusty clamps get a handful of proper ones, which could be moved without fear of breaking them.
Rather unsurprisingly I gave the engine a good wash, when I fired the fuel pump up for the first time, because all the injector o-rings were in a rather sorry state. (Luckily the ones used are generic items.)
On the plus side: the engine fired up and ran terribly, but it was enough for everything to heat up sufficiently, so I could pull the injectors, which were then replaced with a slightly less manky set.
Still, it wouldn't really run right. So a serious amount of investigation was due. I think, if there were a list of "typical spots for air leaks on a flying brick", I would have scored a full house.
At this point, I still though it would only be a case of a slightly squashed o-ring on the air-screws and tried my luck with a bit of vaseline, which for reasons that should become rather apparent quickly, was completely pointless.
And a bit more fire damage - choke switch was damaged and the airfilter as well. (Which is hardly surprising.)
So a fair bit of ordering parts was due...
