TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. > Project Classic Motobricks

92 k75s and a particularly dumb idea

(1/10) > >>

Kt88:
I’m a serial monogamist when it comes to motorcycles. I’ll only keep one at a time, and I’ll pour my myself into it, but when a new project catches my eye- well, the heart wants what the heart wants.

I’d just sold my 71 r75/5 after bringing it back from a circa 1980 slumber, having ridden it around for a year or so.

65D424DC-BD26-48D1-A00A-B516BADAECFD.jpeg (57.43 kB . 768x511 - viewed 471 times)

Lo and behold, delivered to my eyes was my next obsession: a derelict k75 down in the Florida Keys.

C401560E-95E3-43E5-840C-0C50372E0966.jpeg (105.84 kB . 640x479 - viewed 461 times)

Now, other life occurrences meant I have a shoestring budget (good for a derelict k75), no truck (bad for a derelict k75), and about a day to make this all come together. Compounding my sense of urgency, this bike was priced as if it weren’t in South Florida, where there’s got to be some rust tax that adds 1k to every asking price for some reason I’ve yet to fathom.

So the plan, as dumb as it is, is to go down and rouse the machine and.. ride it back. It’s only 80 miles, what could go wrong?

My better half and pup go down with me and my trunk of tools. Upon arrival, I recognize that pictures were kind, and salt air isn’t. Everything is crusty and rubber is a flimsy concept rather than a pliable material. If it were easy, though, it’d not be an adventure, right? ..at least that’s what I told my wife as she watched this calamity unfold.

All told, major items that were kaput:
Fuel pump and filter (expected)
Sending unit (was hoping it wouldn’t have lost continuity but.. darn)
Front master cylinder (frozen dry and filled with powder)
Front tire (valve stem rotten)
Rear shock frozen upon first compression
All keyed cylinders frozen (one key only, better be gentle)

New battery, drained and flushed tank, but old fuel pump was unsalvageable. The auto parts stores down in the keys could get a Bosch pump that crossed over part numbers, but they.. forgot to put it on the truck when I ordered it. I cobbled together a pump, sock, and wiring from a Chevy application that had similar gph ratings and was on hand- I’ll go stock once I have parts in hand.  The sender unit solder had let go, so for the moment, I am powering the pump from the four pin connector to wires coming in through the gas cap. Very classy!


D1C48258-2099-41CE-8645-588AD8229047.jpeg (49.92 kB . 432x576 - viewed 464 times)

Once the pump was pumping upon turnover, I verified we had spark (strong), and cranked. No dice yet. Pulled the fuel rail, sprayed off the ends of the injectors, then reassembled to a bunch of new little rail leaks from old o-rings. A couple washers on the rail to increase the pressure on the o-rings later, we have seals, and magically, we have engine life.

The rear brake bled out well, relatively speaking. The front MC will need complete rehab- at this point, it’s Sir Not Appearing In This Film. However, it’s worth noting that after a year of r75/5 riding, my braking distances mentally are measured in half miles anyway.

The front tire isn’t holding pressure. Upon examination, the valve stem is leaky around the seal. I’ll clearly get new tires, but to get home I use self sealing silicone tape around the stem. Probably one of the most willfully moronic things I’ve ever done, and surely I won’t repeat that choice.

8376A3C0-5C3F-492A-A024-44519C561D31.jpeg (166.02 kB . 640x480 - viewed 465 times)

I replaced all the fuel lines, the overflow reservoir line, and hit the magic button. Off we went. Wife following me, we took our sweet time and turned an 80 mile trip into a 2.5 hour amble (then again, the Keys are generally 45 mph, so it wouldn’t have been terribly different under normal circumstances, either)

After exactly no real drama, other than some fueling misbehavior at the very end of the ride after an hour of freeway, the bike is in its new home, safe and sound. And the process of correcting hack mechanic work and the ravages of time begins.

31F2CE6A-F727-43EC-A4C8-3273E9101D20.jpeg (38.98 kB . 432x576 - viewed 441 times)


Now for the fun: disconnecting the 90s era alarm system (titan 3003), identifying another clear PCB accessory wired in with no brand name of any kind, returning stock functionality in all systems, and cosmetically freshening the bike up.

I’m not into modifying bikes these days- I’ll keep it stock as appropriate, with possible suspension upgrades.

One note, and maybe I’m preaching to the choir:
Coming from airheads (I’ve had about 35 or so), I’ve always been told a k75 is a great engined bike, but has no character. Riding back under very far from ideal circumstances last night, I didn’t feel that way at all. I would have screamed for joy for my R bikes to run as smoothly as this abandoned k75 did last night. I would have started threads on ADV detailing how I got there. I’d have written novels about the smooth tractability of the power. Do people just not like the K architecture as much? The frame felt great, and I had NO rear suspension. I can only imagine how much more I’ll love it with actual function.  Is this me having rose colored glasses on because I moved from a bike built in 71 to one built in 91?

Anyway. I’m currently in love and can’t wait to make the bike fully functional, safe, and a daily again.

Chaos:
Great story, kudos for not trailering it or giving up.  I always thought the K75s had character, the smoking start ups, extreme side stand lean angle, stock windshield that basically just generates noise, mine even fouled a plug occasionally. Imagine if it were perfect how boring it would be.

Kt88:
Ha, thanks. The to do list that beckons once I’m through with work today:

Replace front valve stem
(Maybe) boil front master cylinder to try and free it up?
(If there’s time) take rear shock off to see if I can make it, I dunno, move at all?
(Definitely not today, maybe tomorrow) go get new injector o-rings so I can stop using extra washers to seal the rail- as the extra washers that were on hand were in fact actually cabinet corner hardware and not even kind of inconspicuous.

The Mighty Gryphon:
Great story!  Sounds like an episode of Roadworthy Rescues.  I have had two K75's an RT and an S like yours.

I think the problem with the Bricks is that the traditionalist airhead/boxer fans have spent nearly 40 years bad-mouthing them.  I have found mine to be super reliable, bulletproof and capable of running 85+mph smoothly for as many 800 mile days as I could handle.  They are great Iron Butt machines.  I have easily kept up with and even pushed guys riding 1000 and 1200cc machines on the interstate as well as the mountains.

They are cheap for what you get, easy to work on, and parts are still easy and not too expensive to find. 

Kt88:
Replying while trying to re-seat a bead at home sans compressor on rock hard sidewalls:

I think there’s also some aversion amongst the airhead-only guys to really rev these. Despite being told for years that my type 247s could live just fine at 5k+, I tended to still cruise around 4500.  So for the most part the enjoyable bit of the engine was low speed torque.

Now keep in mind 90% of my riding with this is with a flat front tire (sweet lord I’m a moron), but my feeling is this will take mildly more clutch work and much more revs to find the happiest point for the drivetrain. I’m fine with that. I think I’ve definitely put enough time in on the R twins to have a good idea about the attractive parts to those bikes, and I’m mostly excited to figure out new things to love about these.

Now to check on the tire, suspended above a boiling master cylinder- hopefully it will become pliable enough to seat the bead with a ratchet strap and foot pump, as that’s what I’ve got.

Navigation

[0] Message Index

[#] Next page