New member from Florida

[Hard Hat]

Hey everyone - new guy here though I have been lurking around a bit. I've been riding bikes since I was about 10. Started with a little Honda trail 50 moved on to small dirt bikes and then street bikes of various sizes. Currently riding a Harley but I am looking at possibly pulling the trigger on an older K75. This would be my first exposure to a bike with a radiator and shaft drive - never had either on any bike I've owned. Is there a good resource to give me an idea of what to look for/at concerning the shaft drive and coolant system during a pre-purchase inspection? I'm definitely not afraid to wrench on it if needed but I want to try to make sure I'm not buying a piece of junk. Any helpful direction would be appreciated.

[Chaos]

worst thing is a bike that's been sitting a long time.  Gas, rubber bits, brakes, you probably knew that.  Check for coolant or oil leaking out of a drip hole at the very front bottom of the engine.  That's a sign the oil/water pump need replaced, expensive.  If you can pull the rear drive off and check the driveshaft splines.  Known weak spot, they need lubed about every 20k miles.  A well maintained K75 will last forever, mine's got about 190K on it now and the engine-fuel-coolant-systems have never been touched except for routine stuff.  Did have a bent shift fork in the tranny around 100k, so they are not perfect. 

[Laitch]

Welcome, Hard Hat!

The Technical Libarary here is the place to go for an idea of how these bikes operate. Here is a source that also explains many of the idiosyncrasies of these bikes.

[Hard Hat]

Thank you both for your input. I actually did run through the tech library a bit to get a general overview of the bike. I was looking for a little insider knowledge on the bike from people with first hand experience. Sometimes there are things you don't know to look for unless someone gives you a "heads-up" and you guys helped me out. It looks as though you can't really check out the drive shaft without some disassembly and I doubt that I will get that chance. I'll just ask a lot of questions, listen for alien noises, and hope for the best. Still have to convince my wife that I need this thing. 

[The Mighty Gryphon]

A few things from personal experience: 

First, there should be almost no free play in the shifter.  If there is, it indicates that a grub screw in the transmission has backed out.  Tightening the screw requires nothing much beyond some blue Loctite.  However, it is about is about an 8-10 hour job which also includes doing a clutch and drive shaft spline lube, fluid changes and, if you want to include it, brake service with new pads and a bleed.  when you're done you have a fully serviced drive train.

Check the rear brake master cylinder.  It's at the low point in the system and any loose water will collect there and corrode the bore.  Pull the boot and see if there is any fluid there.  This could be a $250+ repair for just the parts.

Look in the radiator overflow tank to see if there are any mineral deposits in it.  You might also want to slide the tank back and check in the filler as well.  Mineral deposits means a previous owner used tap water in the system and as a result there is reduced cooling and the engine will have a tendency to run hot.  There is not a lot of reserve cooling capacity on these bikes so the system needs to be kept clean.  A couple of flushes with distilled water and a cooling system flush will get things back to the way they should be.

With the bike on the center stand start it up and put it in gear and look at the rear wheel to see if it runs true.  With the front, you will need someone to sit on the bike to lift up the front end so you can turn the wheel. 

While on the wheels, get a caliper or micrometer to measure disc thickness.  Should be more than 0.140"  Replacing worn discs can be a very expensive proposition.

Look inside the fuel tank.  There are four phillips screws that hold the filler on.  If the internal flapper is in place you will need to remove the filler to get a good look inside to see if there is any corrosion going on or if the rubber mount for the fuel pump has turned to a gooey mess.   Bring a good phillips screwdriver to remove the screws as they may be pretty hard to remove and you don't want to bugger the heads.  Some sellers won't let you go in there unless going in the tank is a deal breaker.

While on the tank, look carefully along the the bottom edges at the lowest point for any signs of gas stains or paint bubbles indicating that water in the fuel has corroded the inside of the tank. 

Splines are a crap shoot.  I have bought three bricks and looked at several others.  I have never  had a seller agree to let me pull the final drive to look at the splines. 

[kris]

Hard Hat, as you know there are no guarantees in life! But the odds are better than 50/50 that your future Beemer will be pretty solid. I picked up a K100 that had been sitting for 9 years (not running). The gas was putrid. There was residue on the inside of the tank but the seams were fine. Lots of scrubbing and the thing shone like new. The tanks are aluminum. My bike had 61,000 miles on it. The log book indicated various service checks done (no specifics on the work) up to 42,000 miles. I found that book after I bought the bike. When I pulled it apart to check rear main seal, clutch, splines, clutch cable boot, etc., etc., I was pleasantly surprised to see that the splines looked like new! And the driveshaft U-joint will have a light click at center. This is, apparently, normal according to Bruno of Iron City, Ontario. He is the driveshaft rebuild/ final drive guru for these machines.  My rear brake cylinder leaked a wee bit after I flushed the fluid and then stopped after being used a bit. Hasn't missed a beat since. The throttle body rubbers will likely need replacing. The weird Z breather pipe for the crankcase (?) will also need to be changed (no biggie). The rotors could be a pain in the ass and expensive. Mine are close to minimum spec but I am very easy on my machine. My brake fluid looked brand new (got changed).  Tranny fluid and final drive looked fine (got changed). The rad flowed like Niagara Falls with no signs of corrosion. According to many, these rads are over-sized for the machine. Might want to make sure the rad fan runs. Mine runs but the damn relay doesn't seem to work. I've been riding this bike for almost two years and the fan has never run. I will be installing a manual fan switch. Best bet is to get one that is on the road at time of purchase, I think.  Hopefully, the seller will be able to give you some kind of maintenance history.
As for convincing your wife....not sure what to tell you. I use the "age" approach. Not gettin' any younger and I could be dead tomorrow....so may as well go for it!

[Chaos]

I just realized if I were trying to sell my bike and the potential buyer looked here for advice, his wallet would sphincter shut and he would run away screaming and laughing!

[kris]

Chaos, that made me howl!! :hehehe Well done. Most guys just wanna turn a key, push a button and go! Never mind this physical exam and tear-down....

[jakgieger]

I just realized if I were trying to sell my bike and the potential buyer looked here for advice, his wallet would sphincter shut and he would run away screaming and laughing!

   :hehehe :hehehe I bought mine before looking/finding Motobrick.  So now, my cheap classic motorcycle cost me an extended European vacation .  Still don't regret it when I feel her beneath me purring.  That being said, BE PATIENT.  Right after I bought mine, an identical RUNNING bike came up for sale for 800 less :yow

[Laitch]

I should have bought a KLR650.

[The Mighty Gryphon]

I should have bought a KLR650.

Had you done that, we here, much to our collective chagrin, would have been deprived of your Green Mountain Polecat wisdom.

[stokester]

Hey everyone - new guy here though I have been lurking around a bit. I've been riding bikes since I was about 10. Started with a little Honda trail 50 moved on to small dirt bikes and then street bikes of various sizes. Currently riding a Harley but I am looking at possibly pulling the trigger on an older K75. This would be my first exposure to a bike with a radiator and shaft drive - never had either on any bike I've owned. Is there a good resource to give me an idea of what to look for/at concerning the shaft drive and coolant system during a pre-purchase inspection? I'm definitely not afraid to wrench on it if needed but I want to try to make sure I'm not buying a piece of junk. Any helpful direction would be appreciated.

I add my welcome to you Hard Hat.

I've found this site is the best for information regarding the Flying Bricks.  My '93 K75S has been a faithful steed for quite a number of years now as a touring bike and a commuter mule.  I did my research, found a well-maintained bike and zero-timed all the maintenance items and fixed, or had fixed in this case, the ABS. 

It's a wonderful ride and really easy to maintain.