• Welcome, Guest! We hope you enjoy the excellent technical knowledge, event information and discussions that the BMW MOA forum provides. Some forum content will be hidden from you if you remain logged out. If you want to view all content, please click the 'Log in' button above and enter your BMW MOA username and password.

    If you are not an MOA member, why not take the time to join the club, so you can enjoy posting on the forum, the BMW Owners News magazine, and all of the discounts and benefits the BMW MOA offers?

Considering adding a 92 K75

If the fan is of the original stock type, then they are stiff to turn, not like a spiral fan.

That is not true (no offense intended). The fan motor has brushes and bronze bushings,so it will not spin as freely as a brushless ball bearing motor, but it should spin easily. You should be able to spin it and not have it stop the instant your finger leaves the blade. It should rotate at LEAST a full turnafter your finger leaves the blade.

Now it IS COMMON for K75s to have stiff fans, it is not because they are supposed to be that way, it is because they are on their way to failure if not addressed.

The early K fan motors are a common source of failure due to a couple factors. They are very light duty. One rumor has it that it was originally designed by Bosch as a Porshe 911 defroster fan motor. As previously stated, they have bushings, not bearings. They run infrequently. They are directly in the dirty airstream behind the radiator. They dirt, grit and moisture pack between the shaft and the bushing for months on end during the coller weather when the fan isn't needed. The in the middle of the summer, when you're in stop and go traffic or stopped at series of long lights, it decides to turn on. The extra drag on the motor shaft causes a rise in current demand. The extra current causes excess heat inside the motor. The extra heat burns out the windings OR melts the PLASTIC brush holders and frys the motor.

You might not notice that the fan is out, other than the horn stops working since it is on the same fuse, until the overheat light comes on (if the bulb is still good and they are paying attention to the gauges). Overheating the engine can do all kinds of damage.

The fan motor, the rear splines, the crankcase vent hose, dissolving fuel pump vibration dampers, dirty starter commutaors, dirty ignition switch contacts, and ignored valve adjustments are the most common failures on early Ks if not monitored.




:dance:dance:dance
 
That is not true (no offense intended). The fan motor has brushes and bronze bushings,so it will not spin as freely as a brushless ball bearing motor, but it should spin easily. You should be able to spin it and not have it stop the instant your finger leaves the blade. It should rotate at LEAST a full turnafter your finger leaves the blade.

Now it IS COMMON for K75s to have stiff fans, it is not because they are supposed to be that way, it is because they are on their way to failure if not addressed.

The early K fan motors are a common source of failure due to a couple factors. They are very light duty. One rumor has it that it was originally designed by Bosch as a Porshe 911 defroster fan motor. As previously stated, they have bushings, not bearings. They run infrequently. They are directly in the dirty airstream behind the radiator. They dirt, grit and moisture pack between the shaft and the bushing for months on end during the coller weather when the fan isn't needed. The in the middle of the summer, when you're in stop and go traffic or stopped at series of long lights, it decides to turn on. The extra drag on the motor shaft causes a rise in current demand. The extra current causes excess heat inside the motor. The extra heat burns out the windings OR melts the PLASTIC brush holders and frys the motor.

You might not notice that the fan is out, other than the horn stops working since it is on the same fuse, until the overheat light comes on (if the bulb is still good and they are paying attention to the gauges). Overheating the engine can do all kinds of damage.

The fan motor, the rear splines, the crankcase vent hose, dissolving fuel pump vibration dampers, dirty starter commutaors, dirty ignition switch contacts, and ignored valve adjustments are the most common failures on early Ks if not monitored.




:dance:dance:dance


:thumb:thumb:thumb:thumb

I check the fans on my two K75s at least twice every year, and if they don't turn as Lee described, then out they come for a cleaning and lubrication. And, I watch the other stuff Lee listed, as well. All of those things do not go bad suddenly, so checking them a couple of times a year should give you plenty of warning to allow in-garage service on your schedule rather than on the side of the road.
 
:thumb:thumb:thumb:thumb

I check the fans on my two K75s at least twice every year, and if they don't turn as Lee described, then out they come for a cleaning and lubrication. And, I watch the other stuff Lee listed, as well. All of those things do not go bad suddenly, so checking them a couple of times a year should give you plenty of warning to allow in-garage service on your schedule rather than on the side of the road.

After 35 years, almost everyone in the BMW community has heard that "early K bikes run forever" Unfortunately, over the past couple decades (and second, third and later owners) some have forgot, ignored, or never heard the second half of that sentence; "WITH PROPER MAINTENANCE"! Admittedly, the maintenance usually isn't much, but you at least have to still check things more often than you would on a modern car. Anything goes wrong on a bike, you fall down!

On a bike that has a short list of common, simple issues, ignoring inspecting them until they fail is not very smart. Remember the old Fram commercial; "You can pay me now or you can pay me later".



:dance:dance:dance
 
After 35 years, almost everyone in the BMW community has heard that "early K bikes run forever" Unfortunately, over the past couple decades (and second, third and later owners) some have forgot, ignored, or never heard the second half of that sentence; "WITH PROPER MAINTENANCE"! Admittedly, the maintenance usually isn't much, but you at least have to still check things more often than you would on a modern car. Anything goes wrong on a bike, you fall down!

On a bike that has a short list of common, simple issues, ignoring inspecting them until they fail is not very smart. Remember the old Fram commercial; "You can pay me now or you can pay me later".



:dance:dance:dance

I don't think you can go wrong using the BMW factory maintenance schedule as a guide. I augment it with things like we are discussing, plus spline lubes, but by staying an a schedule I've never had anything catch me by surprise and had no problems on the road. These bikes will run forever but in my experience things that "last forever" require periodic maintenance to do so, and I've found that things stay put on a serviced K-bike. Disposable things, OTOH, can be let go. :brow

I've attached a copy of the BMW K-bike service schedule, and also a document I put together for someone on the Forum who was buying a K75 and PM'ed me for a list of things to check. Lee, I would very much appreciate your input on that document for corrections or additions.
 

Attachments

  • K75RT-K1100RS-LT.pdf
    41.3 KB · Views: 13
  • BMW K100 and K75 Service Information.doc
    50 KB · Views: 12
Greg,

As to the factory maintenance schedule:

The air filter change schedule is excessive unless you ride a lot of dirt.

The timing chain rail change is excessive.

Upper clutch cable barrel should be cleaned and lubed at least twice a year (a seized barrel is the most common cause of cable failure)


The biggest disagreement that I have is what is NOT on that schedule:

REAR SPLINE LUBE (interval depends on how often you want to buy a new $400 driveshaft and/or source a good final drive) I recommend every rear tire change or every 5k MAX, I do mine every 3K (I'm rough on tires). I recommend: https://www.beemershop.com/product/ts-60-spline-lube.html

Check fan

Check and replace crankcase vent hose

Check valve body vacuum caps

Coolant level should be checked AT THE RADIATOR CAP once a year and before every long trip

Clutch freeplay should be checked EVERY RIDE! It's amazing how many people bring me their bikes for service and it has NO freeplay. No freeplay damages the throwout bearing and will accelerate clutch wear.

:dance:dance:dance
 
Last edited:
Greg,


Your list of things to check is very good and helpful.

I only have four minor comments:

9. Monkey Nuts

The impellers are 3 bladed.



11. Backfiring

The first thing I would check is the throttle position switch adjustment, then follow with the things you suggested.


15. Checking the valves

c.
I would HIGHLIGHT that you are suggesting putting the sealant ONLY on the head/ timing cover seams and the half moon seams, NOT the entire V/C gasket. The gaskets don't need it and having to clean excess sealant off V/C gasket surfaces will DOUBLE the time it takes to check the valves.


e.
Bolt grommets/bolts

A very misunderstood subject.


The bolts are not what holds the clamping pressure on the V/C gasket.

The bolts have a shoulder that BOTTOMS OUT on the head surface and the tops of the cam journal caps. It is CRITICAL that these not be overtightened (6 1/2 ft/lb= 78 INCH/lb). Otherwise you run the possibility of stripping out the tops of the cam journals as these are a very low grade aluminum. Helicoiling these is not easy as the threads are deeply countersunk. HIGHLY recommend getting a 1/4" drive INCH/lb torque wrench. HF on sale for $10 will work just fine. Ft/lb torque wrenches are not accurate enough that far down on their scale.

What generates the clamping force to the V/C gasket is the compression/elasticity of the grommets. Over time and with heat cycles the rubber looses its elasticity and hardens to a thinner state which applies less pressure to the gasket and more chance of leaks. Because of the shoulder on the bolts that is already bottomed out on the head and cam journals, tightening the bolts will NOT pull down the cover. It WILL pull out the threads.

Those grommets should always get changed ($1ea, K75 10ea, K100 12ea.) on your 1st valve check on a new to you bike. Always have a set on hand and inspect at future valve checks. Keeping these grommets soft and pliant is as or more important than replacing the V/C gaskets. V/C gaskets can be reused several times with good bushings.

Sorry for the long winded reply on this last one, but it is one of my pet peeves that I see on alot of peoples bikes that they don't seem to understand.:blush


:dance:dance:dance
 
Last edited:
Lee and I are on the same page. He really knows what he is talking about. I have had the maintenance responsibility for something over 600,000 miles of K75s, Including 370,000 miles on "Old Smokey, my 2 time Iron Butt Rally bike, and I still own two.

Driveshaft splines - lube every tire change.

Fan: I replaced on on a picnic table in a state park. I modified one with a brass tube directed down from the top to the nose bearing. A few drops of "sewing machine" oil once a year eliminates most risk of it binding up.
 
Bolt grommets/bolts

A very misunderstood subject.


The bolts are not what holds the clamping pressure on the V/C gasket.

The bolts have a shoulder that BOTTOMS OUT on the head surface and the tops of the cam journal caps. It is CRITICAL that these not be overtightened (6 1/2 ft/lb= 78 INCH/lb). Otherwise you run the possibility of stripping out the tops of the cam journals as these are a very low grade aluminum. Helicoiling these is not easy as the threads are deeply countersunk. HIGHLY recommend getting a 1/4" drive INCH/lb torque wrench. HF on sale for $10 will work just fine. Ft/lb torque wrenches are not accurate enough that far down on their scale.

What generates the clamping force to the V/C gasket is the compression/elasticity of the grommets. Over time and with heat cycles the rubber looses its elasticity and hardens to a thinner state which applies less pressure to the gasket and more chance of leaks. Because of the shoulder on the bolts that is already bottomed out on the head and cam journals, tightening the bolts will NOT pull down the cover. It WILL pull out the threads.

Those grommets should always get changed ($1ea, K75 10ea, K100 12ea.) on your 1st valve check on a new to you bike. Always have a set on hand and inspect at future valve checks. Keeping these grommets soft and pliant is as or more important than replacing the V/C gaskets. V/C gaskets can be reused several times with good bushings.

This is very good information- thanks Lee.:beer
 
I guess I'm going to being going against the flow here, but I'll say it. That looks to me like a very nice K75; clean, good paint, "garage kept" and only 57K miles. It looks VERY well cared for. A tank cover, side cases, windshield... someone really liked that bike. $2500 seems like a fair price for that machine. Yes, it may need a few things, but everything you buy used does.

Personally, I have gotten extremely tired of everyone wanting to get everything for nothing. "What's the least you will take for it" is my favorite response from these people, and that's in an email before even looking at the item. I'm supposed to bargain myself down for them. Just when did "low balling" everything become the norm? Perhaps we have reality TV to thank for that.

It's the guys bike, he can sell it for whatever he wants to. But I think offering $1000 for that bike would be a pure insult. I would hope the guy would just roll the bike back into the garage without a word. I would.
 
John,

I acctually agree with you. The bike looks great and probably worth close to the asking price. It would definitely be worth the asking price once it is running correctly.

I am just pointing out what could be wrong with a K75 that had sat for awhile. When buying a bike, you have to look at the bottom line, but offering someone $1000 for a bike that would cost you $100-200 to make right is, especially when it looks as nice as this one, is kind of insulting. The mechanical stuff is easy to fix, not so much the cosmetics. It's not like it's worn out or trashed. It is just probably something minor. I would buy it,if I needed and had room for an 8th bike!





:dance:dance:dance
 
Just to set the record straight, here’s the next chapter:

After my second 3-hour round-trip to further investigate this bike and it still not starting...and finding the fan problem (and lifting the tank bra and finding concealed tank damage) I went home.

I did not make an offer, telling him I wanted to see it running and ride it before discussing price.

He texted me two days later and offered to sell it to me as-is for $2300.

I politely passed on the offer w/out making a counteroffer and wished him good luck, told him if he could get it running to reconnect with me.


Sent from my iPad using Tapatalk
 
Would the “concealed tank damage” be a leak, at one of the seams?

Seen this a few times with K bike aluminum gas tanks. They can be repaired.

Just to set the record straight, here’s the next chapter:

After my second 3-hour round-trip to further investigate this bike and ...... (and lifting the tank bra and finding concealed tank damage) ......
Sent from my iPad using Tapatalk
 
Would the “concealed tank damage” be a leak, at one of the seams?

Seen this a few times with K bike aluminum gas tanks. They can be repaired.

Yes, but ...

Full honesty ought to be expected and provided. Finding something undisclosed ought to kill any further thought of a deal. Hide one thing, what else is hidden.
 
Paul,

I think you are right. I initially missed the part that the damage was under a tank cover. I was thinking it was under the tank, where some K fuel tanks have seam splits.

Yes, but ...

Full honesty ought to be expected and provided. Finding something undisclosed ought to kill any further thought of a deal. Hide one thing, what else is hidden.
 
Yes, but ...

Full honesty ought to be expected and provided. Finding something undisclosed ought to kill any further thought of a deal. Hide one thing, what else is hidden.
When I got there and it wouldn’t start would be the end of the deal for me I’ve been to look at to many bikes that were in good running condition that wouldn’t even start.
 
John,

I actually agree with you. The bike looks great and probably worth close to the asking price. It would definitely be worth the asking price once it is running correctly.

I am just pointing out what could be wrong with a K75 that had sat for awhile. When buying a bike, you have to look at the bottom line, but offering someone $1000 for a bike that would cost you $100-200 to make right is, especially when it looks as nice as this one, is kind of insulting. The mechanical stuff is easy to fix, not so much the cosmetics. It's not like it's worn out or trashed. It is just probably something minor. I would buy it,if I needed and had room for an 8th bike!
:dance:dance:dance

Lee, I'd be the last person on earth to question your intuition about K75 machines. And that certainly wasn't my intention. All the follow up advice you, and others gave about what to look for in these machines is dead on. A couple of times now I've bought BMWs without looking at the final bottom line, as you suggest, and ended up very seriously regretting it. You get what you pay for is all too true.

It looks like I was too quick to come to the sellers defense judging from the problems the prospective buyer uncovered, and the fact that the seller still thought the bike was worth $2300. I'd say that the adage, "Beauty is only skin deep" certainly seems to apply to that bike. Paul too, is absolutely right about people being honest about what they are selling, which that guy quite clearly is not. Good for you, Rangemaster, you may well have done yourself a big favor by walking away.

In my youth I couldn't pass up buying run down MG Midgets to fix up and drive. My wife claimed that I " felt sorry for them." Yes, I guess that was true. I'm hoping I've finally gotten cured of that. Some cars, and motorcycles, are just not worth the trouble, no matter how "cute" they are.
 
Lee, I'd be the last person on earth to question your intuition about K75 machines. And that certainly wasn't my intention. All the follow up advice you, and others gave about what to look for in these machines is dead on. A couple of times now I've bought BMWs without looking at the final bottom line, as you suggest, and ended up very seriously regretting it. You get what you pay for is all too true.

It looks like I was too quick to come to the sellers defense judging from the problems the prospective buyer uncovered, and the fact that the seller still thought the bike was worth $2300. I'd say that the adage, "Beauty is only skin deep" certainly seems to apply to that bike. Paul too, is absolutely right about people being honest about what they are selling, which that guy quite clearly is not. Good for you, Rangemaster, you may well have done yourself a big favor by walking away.

In my youth I couldn't pass up buying run down MG Midgets to fix up and drive. My wife claimed that I " felt sorry for them." Yes, I guess that was true. I'm hoping I've finally gotten cured of that. Some cars, and motorcycles, are just not worth the trouble, no matter how "cute" they are.


This post is a bit too civil... :brad


I'd also walk away, only because there are so many other good condition, running K-bikes out there... the current marketplace shows a couple under this seller's asking price...
 
Lee, I'd be the last person on earth to question your intuition about K75 machines. And that certainly wasn't my intention. All the follow up advice you, and others gave about what to look for in these machines is dead on. A couple of times now I've bought BMWs without looking at the final bottom line, as you suggest, and ended up very seriously regretting it. You get what you pay for is all too true.

It looks like I was too quick to come to the sellers defense judging from the problems the prospective buyer uncovered, and the fact that the seller still thought the bike was worth $2300. I'd say that the adage, "Beauty is only skin deep" certainly seems to apply to that bike. Paul too, is absolutely right about people being honest about what they are selling, which that guy quite clearly is not. Good for you, Rangemaster, you may well have done yourself a big favor by walking away.

In my youth I couldn't pass up buying run down MG Midgets to fix up and drive. My wife claimed that I " felt sorry for them." Yes, I guess that was true. I'm hoping I've finally gotten cured of that. Some cars, and motorcycles, are just not worth the trouble, no matter how "cute" they are.

Funny you should mention MGs...I used to had that affliction as well [emoji1787].

I’ll just wait and see what the seller does...I have learned to be patient about such things.


Sent from my iPad using Tapatalk
 
Funny you should mention MGs...I used to had that affliction as well [emoji1787].

I’ll just wait and see what the seller does...I have learned to be patient about such things.


Sent from my iPad using Tapatalk

It took two MG's and a bucket of money to cure me. :D
 
Back
Top