New member project bike.. 1987 K75

So being a newbie, I am hoping that I can put up here my project bike and pics.

Before I do so, I want to make sure folks would like to see this.

Its a bike I just purchased the other day and is a craigslist special. (Ergo: mechanics special).

There is a lot of work and if allowed I will post information on what I am doing and will take any and all advice into consideration to what I am doing. In other forums, I have found some allowing multiple photos and others requiring links. So before I journey off into this foray, I wanted to get input from those in the know about all of this.


Thanks in advance.

We like projects and we REALLY like pctures. Post away!

We'll help you out anyway we can.

Photos need to be under 152mb and only 3 per post max, but you can put as many 3 picture posts you want in a thread.

Please always put the year, model, and sub- model (C, S, RT, etc) in the TITLE of any thread that you start.

So the bike is an "RS".

So far what I have found is that the bike was repainted (poorly) the Odometer was banged up, and the relay flashers need to be replaced.

There are a lot of quirks so far that I have found including needing a new air intake snorkel and the fuel sending unit is totally destroyed.

As I was cleaning the gas tank out (looked like a lot of rust) it turned out to be the residue of someone using non-submersible rubber hose on the fuel line.

They also jerry rigged the fuel pump and sending unit on the wiring harness coming out of the tank.
So I am going to have to replace that.


The RH mirror was missing the glass and the housing cracked so I am going to replace both with something else.

So I have a fair amount of work ahead of me, and Ill post first the bike as it is.

Then Ill show some of the more evil repairs Ill make.

It looks like so far that someone did a first class hatchet job on the front end of the bike. The front turn signals look like something of of an old Shovelhead and the wireing was spliced.
This may answer the question as to why the relay went kaput.

The horn is NOT a beemer horn and the light looks suspicious as well but I'll look later.

The throttle is sticky so the cable prob. needs to be R&Rd.

The lower end of the bike outside the dirt an usual gunk looks ligit. The wiring isn't cut but there are a few items that are not connected.

Soocom,


There was never a K75RS. If the bike has a narrow frame mounted fairing, a disc rear brake, and the last seven #s of the vin are 015xxxx, then it is a K75S.

If it has a small fork mounted fairing or no fairing, a drum rear brake, and the last seven #s of the vin are 013xxxx, then it is a K75C.

The gas tank is aluminum, so there is no chance of rust. The sending unit only does two things on your bike (unless someone has installed the optional fuel gauge). It passes the power through the tank wall to the fuel pump and it triggers the low fuel light when there is somewhere around 1 gallon left in the tank.

You can use standard BMW mirrors that go through the holes in the lever perchs and are held in place with a nut or you can slightly enlarge those holes and tap them to 10mm. You can then use almost any aftermarket mirror. You can still go back to the standard BMW mirrors after you've modified the holes with no issues. BMW mirrors are about $70 ea. Aftermarket mirrors start at around $12 ea. and offer endless styles.

98lee said:

Soocom,


There was never a K75RS. If the bike has a narrow frame mounted fairing, a disc rear brake, and the last seven #s of the vin are 015xxxx, then it is a K75S.

If it has a small fork mounted fairing or no fairing, a drum rear brake, and the last seven #s of the vin are 013xxxx, then it is a K75C.

The gas tank is aluminum, so there is no chance of rust. The sending unit only does two things on your bike (unless someone has installed the optional fuel gauge). It passes the power through the tank wall to the fuel pump and it triggers the low fuel light when there is somewhere around 1 gallon left in the tank.

You can use standard BMW mirrors that go through the holes in the lever perchs and are held in place with a nut or you can slightly enlarge those holes and tap them to 10mm. You can then use almost any aftermarket mirror. You can still go back to the standard BMW mirrors after you've modified the holes with no issues. BMW mirrors are about $70 ea. Aftermarket mirrors start at around $12 ea. and offer endless styles.

Click to expand...

Thank you for that

So first it tells me that its a K75C because of the numbers. its 013.

Good to know on the gas tank, that answers why after cleaning it up it was pristine inside.


This is helping greatly. It looks like the front end was badly butchered by someone trying to do some kind of modification, so if its a C then I need to focus on bringing it to that level.

I am seriously thinking of dumping the round mirrors for something much diff.

The cost ais easy to handle on those.


Quick question then, I take it this isn't an ABS Mod?

(Please forgive some of the ignorance, I am a former Harley type.) As I go through this, I will gladly take suggestions and corrections.

soocom1 said:

Good to know on the gas tank, that answers why after cleaning it up it was pristine inside.

Click to expand...

And why buying a magnetic tank bag might not be a smart move.

soocom1 said:

Quick question then, I take it this isn't an ABS Mod.

Click to expand...

ABS was not an option on K75s until 1990, and never on a drum rear brake bike.

98lee said:

And why buying a magnetic tank bag might not be a smart move.

Click to expand...

I once bought a used K1100. The owner threw in a magnetic tank bag he had bought; complained it never worked very well.
I didn't have the heart to tell him why.

Here is the beast in the before picture.....

Your "C" is also a low-seat version (as evident by the gas tank surround)


A couple notes about the throttle.

The K75/K100's had an option for a throttle lock/poor mans cruise control - if you look underneath the off/starter switch, you may see a small silver knob, turning that out may solve your sticky throttle situation.

I believe the throttle cable itself has a teflon coating inside that the braids wear against. It's generally not advisable to use a cable lube on these.

We will all be watching as you bring this beauty back to life!!

drneo66 said:

Your "C" is also a low-seat version (as evident by the gas tank surround)


A couple notes about the throttle.

The K75/K100's had an option for a throttle lock/poor mans cruise control - if you look underneath the off/starter switch, you may see a small silver knob, turning that out may solve your sticky throttle situation.

I believe the throttle cable itself has a teflon coating inside that the braids wear against. It's generally not advisable to use a cable lube on these.

We will all be watching as you bring this beauty back to life!!

Click to expand...

Found out about the poor mans cruse.. (same concept on the Harleys.)

The low seat I didn't know. As for the cable itself, it looks like a bicycle chain in the hand control housing and not sure how to remove it w/o destroying the controls.

So I am under the impression that a dry lube is in order there?

Its filled with a nasty looking graphite lithium grease and sticks like the dickens attached.
When I unhooked the throttle and cable from each other, the cable moved fairly easily. But when back in the housing, it gets sticky as all getup.

The tires also seem to be diff. as well. The rims are both 18 inch. Is that typical?

Also the rear hub cover is missing and the hub cap/collar is a NLA part.

I am seriously thinking of going back to 130/90 on the rear and keeping the 100/90 on the front. Just a new tire.

Update:

Ok. So the bike is titled, registered and insured.
It is physically moving but some issues are creeping out as I expected.
1: The rubber o rings on the fuel rail are leaking and given that I had to muscle the injectors open, I may just have to out rightly replace them.


fuel was leaking a bit onto the head and there was some odor so that's how I found out.

2: The instrument cluster lights up but doesn't work yet.
So I will need to work on that aspect. The right side turn signal has the relay buzzing.

I don't know if its a bad relay or the fact that I have to replace the front turn signals.

The front fairing is missing (me thinks its the real low profile piece) and the horn (yes singular) is in the wrong place.

The butcher job on the wiring is turning out to be a mostly simple fix and I hope that the only real problem electrical wise is the butcher job they did on the front end.

3: The fuel pump works perfectly and the sending unit went in fairly well, just really tight.

4: The transmission is still a bit sluggish, (expected with an unused older bike) but the bike does pop into and out of gear.

5: The tires were re-inflated and I will watch the condition, but I will replace them before I get onto the highway.

6: The "feel" of the bike improves the more times I run her and do the necessary things to get the o' juices flowing again.

7: There is a question that I do have, is that there is this plug coming off the battery that has the two wires going to each side of the battery, but has no apparent use.

The wires look factory, but I really am not sure. This plug is a white plastic thing with an upper and lower "T" shape. There are no ports, other loose wires or the like that looks like they would connect to this thing.

Does anyone have any ideas?

The only "T" shaped connector that I can think of offhand is the one to the back of an accessory plug. This plug, on a C is usually on the dash pad. It is a Powerlet, BMW, John Deere type receptical instead of a larger cigarette lighter type receptical. Other models had this receptical at the top of the coil cover. The receptical was used for heated gear, running a tire pump, and charging the battery with a BMW battery charger that had that unique connector.

A picture would help.

How old are the tires? Molded into the sidewall numbers that'll show the date of manufacture. If they're more than five years old, don't ride on them - the rubber compounds degrade with age and ozone, and the tires will have impaired traction even if there's reasonable tread.

Looks like a fun project. Your attitude is admirable!

Ill get a pic of the connector later.
The accessory above the coils is already hot. So that makes me wonder it its an aftermarket thing.


The tires are a bit older and I would love to go duel sport, but finding a good compatible tire is a bit challenging.
Because the area I am in there a very few shops that actually mount motorcycle tires Ill wind up doing them myself.


I also found out that the rear drum either needs adjustment or is shot, (there is no real solid rear brake ) and the peg travels to the end.

The speedo and Tach as I said isn't working nor is the Neutral light.


The Choke light comes on and the center triangle-explanation point is lit constantly.

I am scavenging newer Harley Nightster turn signals and though some modifying of some HDPE to make a base is needed for the rear, the front is coming out killer looking.

Mirrors will prob. be a higher quality style. The other mirrors I tried were too short on the thread shank.

The Nightster tail turn signals look really nice in fact, but the buzzer thing is still driving me nutts.

So I pulled the fuel injectors and replaced the o rings.
The bike is running strong with some good torque.

When I went to work the Tach and speedo, I also decided to look at and clean up the headlight.


Well...……………………….…………………………………………..




Here is what I found:



This is the headlight removed from the "housing". Note the hole in the back.

I am strongly assuming that it isn't suppose to look like that.

This is what it looked like on the inside.



What are those two green wires with the torpedo connectors? Anyone know?

Also note the splicing job on the wires with the yellow and blue. That is the horn circuit and only one horn.



The back of the headlight bulb itself and the connecting harness wires look fine, but what are those two wires coming off the harness on each side of the main connection?
They obviously are factory, but are they running light wires?


Please, I humble myself to gurus of the forum.....

Fill me with your wisdom and knowledge.

All brown wires are ground wires.

The extra wire near the headlight connector is possibly a parking light connector. See if it is hot when you turn the key 1 click clockwise from off. You can remove the key in the off position or in this parking light position.

So I have come to realize that the two wires are for a secondary bulb in the CORRECT headlight system.

Ill keep this for now and clean it up until I can replace it with either factory or something new.

But the question i would have it this.

Will the system work fine without that secondary small bulb connected, or will it absence cause an electrical problem?

That secondary bulb is the front parking light. No problem leaving it disconnected IF you make sure it is insulated. Tape will do fine.

OK.. I am a little bummed and am facing a bit of a curmudgeon.


So the original speedo was melted badly by the Arizona sun prior to me getting this bike.

I go to Ebay and find a gauge cluster described as "Excellent condition working..."

Buy the thing and plug it in.
Then start the bike and run the street.
Tach works but speedo is dead.

I take the base off the bike and open it up. On the inside I find this massive layer of rusted waterline going clean across the speedo parts and PC board. its fried!


So I am now wondering if I should try again with a questionable set of gauges off another bike from someone in the UK or NJ, or N'Dele Bamingui-Bangoran Africa for that matter, or do I just bite the bullet, do some serious electrical slicing and put in a brand new digital gauge set onto the bike and call it a day?

Any suggestions either way?