"New" old K75 in the stable

I have just acquired a 1987 K75. I belive it is an "S" model with smallish windscreen and sport fairing. It is a deep red color. It was literally parked in a barn 17 years ago. There are 8K miles on the odometer and aside from being dirty it appears to be "all there" with no visible damage. The PO said it was running fine when he put it up in 1990! However, the fuel system was not drained when the bike was laid up and I anticipate there will be issues there.

I'm an "R" guy and have no experience with these machines but I understand they were considered to be a very reliable powerplant and drivetrain. I did not receive any manuals with the bike and am in need of some advice from my BMWMOA brethren. To wit:

1) A recommendation for a good service manual.
2) What fluids (crankcase oil, tranny, FD) should I use.
3) What fuel octane rating is recommended.
4) It will need tires! I suspect those on it now are the originals. Suggestions?
5) The key I have seems to work the seat/helmet lock but not the ignition switch. Were there two keys for this bike?
6) What spark plugs are suggested?
7) Egads! It's liquid cooled!! Would any 50/50 mix for aluminum engines suffice?

I know I'll have more questions. Thanks in advance for your help!!

Dr. Paul

Some quick answers.

DrPaul said:

I have just acquired a 1987 K75. I belive it is an "S" model with smallish windscreen and sport fairing. It is a deep red color. It was literally parked in a barn 17 years ago. There are 8K miles on the odometer and aside from being dirty it appears to be "all there" with no visible damage. The PO said it was running fine when he put it up in 1990! However, the fuel system was not drained when the bike was laid up and I anticipate there will be issues there.

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First, congratulations on such a find. Once you get the storage issues delt with, you should have a very fine bike.

There are two models of K75 with a factory fairing - the "S" (with a disk rear brake) and the "C" (with a drum rear brake). Both are fine bikes, but the rear tire size is different between the two.

I'm an "R" guy and have no experience with these machines but I understand they were considered to be a very reliable powerplant and drivetrain. I did not receive any manuals with the bike and am in need of some advice from my BMWMOA brethren. To wit:

1) A recommendation for a good service manual.

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Clymer seems to be the most comprehensive. Just remember that all after market service manuals have some errors, so if something seems like whacky advice, no harm in checking it on some of the lists.

http://www.clymer.com/Book.aspx?bid=485&title=BMW+K-Series,+1985-1997

2) What fluids (crankcase oil, tranny, FD) should I use.

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Transmission & grearbox: 80w90, or 90 Hypoid GL5 gear lube
Engine: 15w50

Personally, I go for the synthetic lubricants. However, in your case I'd change the fluids, run the bike for several hundred miles, and change again. Maybe the "good stuff" the second time.

Also, get the BMW oil filter and the special wrench you'll need to change it. You can get those at your local dealer or from the big on-line dealers (Bob's, A&S, Max, etc.)

For fork oil you'll need to know if your bike is an S or a C. They use different specifications.

3) What fuel octane rating is recommended.

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I'd start with premium. These are high compression engines, and many people have advanced the timing to get a bit more performance. If that's been done to your bike, you'll need premium for sure.

4) It will need tires! I suspect those on it now are the originals. Suggestions?

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My suggestions will depend on if your bike is an S or a C since they have different sized rear wheels. There are some tire models which are available for the S but not the C. Also, it would be a big help to to know about your riding style and the kind of roads in your area.

5) The key I have seems to work the seat/helmet lock but not the ignition switch. Were there two keys for this bike?

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Not out of the box. You'll need to get something changed to match something.

6) What spark plugs are suggested?

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Bosch X5DC

7) Egads! It's liquid cooled!! Would any 50/50 mix for aluminum engines suffice?

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No, you need to get a coolant that is silicate & phosphate free. Many of the newer formulations meet this requirement, but check the bottle. Also, BMW recommends a 60/40 ratio (water/coolant).

I know I'll have more questions. Thanks in advance for your help!!

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A couple of other things I'll offer:

Remove and flush the tank, then run several tanks of gas with a rich mixture of Chevon Techron (1oz/gal or more). That stuff is amazing and will do a wonderful job of cleaning the fuel system and injectors.

Get TWO new fuel filters. Replace the one in the tank and keep a new one in the tail piece "trunk" behind/under the seat. The K-bike fuel filters are designed to remove ALL the water in the fuel and can plug with just one or two bad tanks of gas.

Check the crank case vent hose on the back left side of the engine. It's about 8 inches in on the back left corner of the engine. Run your hand over it for cracks. They can crack and leak air which screws up overall engine running. Cheap and relatively easy to replace.

Pull the rear drive off the swing arm and check the drive shaft splines for grease. Unlike your airhead (assuming it's not a paralever) the K-bike drive shafts don't run gear oil - the coupling splines are lubed with grease like the clutch splines on all BMW bikes. Do this about every 10~14,000 miles. By leaving the rear drive hanging off the rear shock and tying it back, you can do this job in less than an hour.

Speaking of splines, like all BMW bikes, the K75 needs it's clutch splines greased from time to time. If you have stiff/sticky shifting, especially from 3rd to 2nd, then you are likely due.

Get the Clymer manual and read it over, but ask all the questions here you want. Hope this helps.

Do NOT attempt to start the bike!!

If the bike was put away without draining the fuel and the fuel level was above the fuel pump vibration damper, the old fuel will have turned the rubber vibration damper to gooo. If you are lucky, and no one has attempted to start the bike, the gooo will be just in the fuel tank (easy and cheap to remedy). If you attempt or someone already has attempted to start the bike, the fuel pump (if it still works) will pump the gooo through the system thereby contaminating the fuel pump and the very fine screens and orfices inside the injectors.

Best plan is to remove and drain the tank.

Remove fuel pump, vibration damper,and filter from the tank.

Inspect inside of tank. It should be clean shiney BARE aluminum (no evidence of any coating) no film of any kind. If so, you might be in luck. If not clean , clean , clean.

Inspect vibration damper. It should be hard with no signs of being desolved by the stale gas. Should have a very distinct groove where it mates with the upper of the two of the bumps around the circumferance of the pump.

BENCH TEST the pump. This way you do not run the risk of further contaminating the system. Small post +. Large post -. If it whrrrs, that's a good thing. If it's quiet or if it hums without rotating, that's a bad thing. Worst case, replace (about $220) best case, bench clean.

Install NEW fuel filter, new or cleaned and working fuel pump, good condition vibration damper, new internal hoses (F.I. and immersion rated).

Now if you try to start it, you will do no further harm to the injectors and it might start.

Make sure you have a VERY good or New battery when you try to start it for the first time. Low battery levels will cause the starter relay contacts to weld together.

Good luck. You will enjoy the bike.

Marvel Mystery Oil

It is safe to assume the piston rings are bone dry. When you change the plugs you may want to squirt a bit of Marvel Mystery Oil into the cylinders and roll the bike back and forth with the transmission in gear, to wet the cylinders and rings. The oil will burn out clean when the bike fires up.

Congrats! The mythical "barn find" lives.

Bob_M said:

Congrats! The mythical "barn find" lives.

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Keep us informed!!

Congrats on the new ride and listen to what Greg and Lee had to say!

Pics, man, pics!

Thanks for the info!!!

Many thanks to Greg, Lee and Bob. Your information is greatly appreciated. Greg, my K75 has the disk rear brake so I guess it is the "S" model. I will order a Clymer for it. Your oil and gear lube recommendations are exactly what I run in my R1150RT. I have a BMW oil filter wrench for my R; I see the K75 has the enclosed filter cavity like my buddy's K1200LT. I think the filter diameters are the same. I've used Beemer Boneyard for many service parts (my local dealer closed this past year) with good results. My R is an oilhead so I'm familiar with the dry shaft. I will lube the splines as you suggest. I presume a suitable moly spline paste is preferred. I'm tempted to go ahead and do the clutch splines while it is apart. Is that a major PITA? Lee, thanks for the suggestions on the fuel system. Do you have a recommendation on a battery? I have the Exide AGM in my R. Is the alternator belt driven and, if so, should I replace the belt on a 20 year old bike w/ 8K miles? Bob, thanks for the Marvel Mystery oil tip. That stuff is great!

I'll keep everyone posted on my progress! Thanks again.

oil filter and fuel filter is same item your R bike uses. Beemerboneyard seems to have a "best price" on Bosch oil filters. The K&N 163 filters are also well rated, and attractively priced http://cyclegear.com/spgm.cfm?L1=&L2=&L3=&L4=&item=TUC_40-1450_G&tier2=142

An S in Marakesh Red?? With only 8000 miles? What a GREAT find!!


Of course I am a little prejudice, Here are two of my three Marakesh Red K75Ss:


Let me know the last five numbers on the VIN# and I can tell you if it was made before mine. Mine was built in the first week of US K75S production and is the 81st K75S built for the US.

BEST battery: OdesseyPC680 or PC680MJ GREAT battery!!

While the tank is off: the radiator filler is under the tank. Flush and fill with fresh coolant. IMPORTANT: the overflow hose from the radiator to the overflow bottle MUST NOT have ANY cracks. If it does it will allow coolant out of the sytem and suck air into the system.

Check to see if the fan can be turned freely.

Honda Moly 60 paste seems to be the lube of consensus.

DrPaul said:

Many thanks to Greg, Lee and Bob. Your information is greatly appreciated. Greg, my K75 has the disk rear brake so I guess it is the "S" model. I will order a Clymer for it. Your oil and gear lube recommendations are exactly what I run in my R1150RT. I have a BMW oil filter wrench for my R; I see the K75 has the enclosed filter cavity like my buddy's K1200LT. I think the filter diameters are the same.

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They should be.

I've used Beemer Boneyard for many service parts (my local dealer closed this past year) with good results. My R is an oilhead so I'm familiar with the dry shaft. I will lube the splines as you suggest. I presume a suitable moly spline paste is preferred.

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Yes. My favorite is the Honda Moly 60. I just checked the rear drive shaft splines on one of my K75s after 10,000 miles and it still had good lubrication.

I'm tempted to go ahead and do the clutch splines while it is apart. Is that a major PITA?

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Depends on your definition of PITA. I would say it is for many folks. Basically, you have to unbolt the rear of the frame from the transmission and rotate it up on the front bolts so you can pull the tranny out the back. You'll have to support the engine from below (scissor jack, etc.), use a cherry picker or make a harness to pull up and support the frame. Nothing here is really difficult, but a good bit of work.

Personally, I'd do this in a couple of stages. First, I'd get the bike cleaned up inside and out (I especially like Lee's fuel system clean/test process), get some good tires, etc. and ride it. You may find the fork head bearing grease has turned to mud - things like that. This assumes the transmission shifting is ok.

Then I'd pull the tranny and do the spline lube, and you'll have it all good for the road. Even with "dry" splines, the relatively small miles you'll put on road testing shouldn't be an issue.

OTOH - you might just want to go through it front to back all at once as a big project, which is just fine as well.

Lee, thanks for the suggestions on the fuel system. Do you have a recommendation on a battery? I have the Exide AGM in my R. Is the alternator belt driven and, if so, should I replace the belt on a 20 year old bike w/ 8K miles? Bob, thanks for the Marvel Mystery oil tip. That stuff is great!

I'll keep everyone posted on my progress! Thanks again.

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Do that - and do post some pictures!

98lee said:

An S in Marakesh Red?? With only 8000 miles? What a GREAT find!!


Of course I am a little prejudice, Here are two of my three Marakesh Red K75Ss:
View attachment 10753

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Oh - VERY nice brace of K75S's!!

Greg,

You are mixing K and R metaphors (or is it semaphors) here. There is no need to move the rear subframe on a K. But, the centerstand is located on the transmission so you have to secure the front wheel very well and block/jack under the sump to support the bike.

But you knew this - you just got your Oilhead and K bike mixed up!

PGlaves said:

Greg,

You are mixing K and R metaphors (or is it semaphors) here. There is no need to move the rear subframe on a K. But, the centerstand is located on the transmission so you have to secure the front wheel very well and block/jack under the sump to support the bike.

But you knew this - you just got your Oilhead and K bike mixed up!

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Doh!!! Either too much - or not enough - coffee today!!!

Update #1

Good evening! And again, thanks to all who have contributed. The two main discoveries today are a shot fuel pump and radiator fan. The fan blade was twisted off the motor shaft and the motor is frozen. I'll bet the motor/blade assembly is not available alone and I will have to buy the shroud as well. Oh, well.

Had to drain the cooling system and remove the radiator to get the fan unit out. The coolant was pretty clean and the system was full so I'm optimistic nothing had frozen. Because the bike had sat with fuel in it for 17 years, I pulled the air box, fuel rail and throttle bodies. I would like to pull the injectors for a good cleaning but I can't figure how to get them out of the head. Advice here would be greatly appreciated. Pulled the plugs and they looked almost new. Filled the cylinders with MMO and will let sit for the night. More later .....

Paul

98lee said:

Let me know the last five numbers on the VIN# and I can tell you if it was made before mine. Mine was built in the first week of US K75S production and is the 81st K75S built for the US.

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Lee,
Those are some beautiful bikes! The last 5 numbers of my VIN are: 50141

Paul

Vin #?

98lee said:

Let me know the last five numbers on the VIN#

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Lee, If you don't mind I want in on this. Here are my last five vin#s 50067
Armando

You're in good hands with this crew -

The only additional contribution I can make is that there are some amaziing internet resources available to augment your Clymer manual -

http://www.ibmwr.org/ktech.shtml

http://bmw.k100rs.free.fr/files/repair_manuals/BMW K1100LT K1100RS - ENG.pdf

Much of what is here will be relevant for your K75.

generous and expert

What a generous, informed, and supportive series of responses to DrPaul's questions! I learned much, as I always do when the experienced share their knowledge in this forum. You guys rock, I must say.

DrPaul said:

Lee,
Those are some beautiful bikes! The last 5 numbers of my VIN are: 50141

Paul

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I WANT YOUR BIKE!!!

Our bikes are sisters from the same litter!
Mine is # 81
Yours is # 141

They were both built in the first month of US spec K75S production May of 1986.
But since they were introduced mid year they called them '87 models.

They built 325 for the US market that month.

Not suprised about the fan. New fan motors are available for $65 and fuel pumps for $200 from a guy who sells all the Bosch stuff for old Kbikes. I'll try to get you his number tomorrow. I might have a good vibration damper for you.

Don't take too many things apart yet. Is the inside of the fuel rail clean or does it have a coating of brownish gooo in it?

If it is clean, put the injection system back together and try to start the bike. If the injectors are partially fouled, running some Techroline in a few tanks might clean them up.

If the injectors are really fouled, it's not worth messing with them. I can tell you where to get rebuilt and flow checked ones for $12ea. no exchange.

If you really must know how to pull the injectors, but don't do it unless:

A. The fuel rail is full of the brown goo
and
B. you have the new injectors ready to put in


Step1
Thoroughly clean aroun the base of the injectors and the head with brake clean and a small brush and finish of with compressed air to remove all traces of sand, grit and dirt that could fall into the cylinder when you pull the injectors.

Step 2
Reattach the fuel rail to the injectors. Do not bolt rail to head.

Step 3
Gently rock the fuel rail (and injectors) to loosen them from the head.
They are only held in by the O-ring that also seals them to the head.

P.S. The rebuilt injectors come with all new O-rings top and bottom.

cafecubano said:

Lee, If you don't mind I want in on this. Here are my last five vin#s 50067
Armando

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Holy Sh*t! It's a family reunion!!!!

Your bike was also built in the first week of production of US spec K75Ss. In fact your bike and my bike were probably built on the SAME DAY. Yours is the 67th ever built and mine is the 81st.

Your next move should be to join BMW NORCAL. I am going to be cohosting a tech session for them in January.

For 2 valve Kbikes I'm going to be offering valve adjustments, throttlebody sync, rear spline lube, tire balance, tire plugging practice and help with any other issues someone might want to look at.

I'm going to Private Message you my phone number since I just live across the bay.
I'll hook you up (since were family and all)

Also I noticed in a previous post that you mentioned about not being happy with the bar placement. I have several options you might want to try.