New kid on the block - k75c

[matjas]

Hello
I have been a way for a moment but been busy with other bikes and projects.
In the meantime I dropped my k11 in a parking lot just turning anround and broke the left mirror, cracked the upper fairing. All in front of a cafe. Bygger!!! This led me to getting rid of the 1100 although I loved the bike ssssoooo much.i really am going to miss it.

But the weight and the constant pressure from the fairing on my knees started to wear out my patience.
Also - the heat!!! This summer did it for me really.

But I managed to find a very nice k75 :) - good service history, 76kkm, all in all very nice bike.
Glad they still can be found.
Now I need to go the unknown path as the beast is leaking somewhere in the front. See pics so it seems like the front cover off time :( no fun. This is however not so bad. The bike has been cleaned thoroughly and degreased - you can see the leak already forming in the front.

Worse is it is leaking gearbox oil through the telltale hole of shame at the bottom of the gbox housing.
The whole bottom of the engine and centrestand was mucky and smelled of tranny oil.
Now I replaced the oil with new 75/140 with the usual MOS2 additive and only after 25kms the weep has changed color :(

As you know I am not afraid of digging into the bike but maybe I am missing something and ofc counting on a miracle. Is that 100% input shaft seal leaking? Wouldn’t that be also caused by the clutch rod transferring the oil somehow from the back of the gearbox??? Just a wild idea…
If not it seems I need to pull the transmission. I so much don’t want to do it but am afraid of soiling the clutch which for now seems to be ok.

While in there I think I will have to replace the crankshaft seal + oring /is there an oring too as is in 1100?/ and maybe see if the clutch disc is still thick enough to let it be for another 50kkm.

Your insight is as always welcome and appreciated.

P.s. I have a leftover mounting piece/platform in front of the oil water pump - I can’t see
Pictures of any lower fairing for the k75c on the internet. What could this be for? PO idea of sorts?

[matjas]

found /i think/ the leak in front of the engine: i think it is one of the screws in there leaking through. When I took it out the hole was full of oil. so MAYBE I will save some time here, clean it all with solvent, degrease and fit the bottom front cover screws with dirko. This should stop the leak. I really do not have much time this time to dig into this and possibly also ruin the Hall seal on refitting the cover.

As far as the gearbox leak is concerned... the question I have: IF this is the input shaft seal leaking will this soil the clutch eventually? IF NOT I could live with it for some weeks until winter and then do it.
Reason for me asking is I know engine oring leak WILL do the clutch. I wonder how far can the oil migrate on the tranny input shaft towards FRONT of the clutch plate splines.

What do you think?

[Laitch]

found /i think/ the leak in front of the engine: i think it is one of the screws in there leaking through. When I took it out the hole was full of oil. . . . 
What do you think?

I think you should post a photo of the screw hole location that is leaking oil.

If there is transmission oil leaking from the weep hole at the joint of the transmission and the engine intermediate housing, it is likely to be a transmission shaft seal or transmission cover seal leaking and oil is flowing directly down the cover and out the hole, not toward the clutch assembly. Cover and seal replacement is not a complicated task.

Have you run the Brick's identification number through a VIN checker to verify what you have? I can tell you it doesn't seem to have a C handlebar or fairing but modification of models is not uncommon.

[matjas]

0251690k75 - real oem does not return any result.

I will take some more pics of the bike. For 75c google returns pictures of bikes with fairings identical to mine so idk.

See the pic: bottom front cover screws and this is the one to the right. Simply the upper portion of the sealing goop must have given up and oil flows into the screw hole and out. Could be same with all three of them. Seems like the cover has never been off - all original factory sealant.

[Laitch]

The result I received is listed below. Does that Brick have a rear drum brake?

[Laitch]

I'm going to answer the question I asked you, matjas, about your K75's having a rear drum brake. It has a rear disc brake.

[frankenduck]

There is a seal at the rear end of the clutch pushrod that keeps the oil in the clutch boot from travelling forward via the hole for the clutch pushrod. In my experience it's more common for that to fail than the trans input shaft seal.

Diagnosis: When you take the trans off check the clutch pushrod to see it if has gear oil on it.




Since the seal is in a metal cup and it's in the trans very tightly it's a bugger to get out.

Use a socket of the same diameter to drive the new one in.

[frankenduck]

I'm going to answer the question I asked you, matjas, about your K75's having a rear drum brake. It has a rear disc brake.

K75C has a rear drum from the factory.

[matjas]

So it is a K75C with a disc brake :)

It seems like I have read it all and ready for the job. What I hate is that for the pushrod seal I need to take the tranny out. On the other hand, though, the clutch spline lube would be nice at this mileage.

p.s. checked the real OEM site in the morning and the input shaft FWD seal is not available in BMW anymore

02   Shaft seal   22X35X7   1         23121451020

Do you think I can use a generic simmerring of the above size? Isnt the seal 'directional' as it often happens in BMW?

what is really bad is that this pushrod seal is also ended...

14   Bush      1      06/1988   23131239891         ENDED


:(
solutions? do you have the dimensions od the pushrod seal?

[Laitch]

We seem to have established via observation and realoem information that your Brick is a 1991 K75 Standard with a low seat, not a C model.

What has not been established is where the transmission fluid leaks out of the moto. The shock absorber adjusting tool has a transmission level line milled into it. If the leak rate is acceptable, check its level with the tool, or an accurate substitute, carry a spare bottle and ride on. If tolerance for uncertainty is in low supply, remove the transmission to find out. My riding season usually ends in the first week of November so if this were my Brick's symptom, I'd keep riding if the clutch weren't slipping. It's a good looking moto. It is likely to handle better if you change the model of tires.
 

[matjas]

Thanks Laitch for the reassuring words.  The seat is indeed a tad low for my long'ish kickers - feels sort of like riding my R80GS :D
RE Tyres - in my 1100 just before selling it I have changed the tyres to Bridgestone T32 - this tyre has really transformed the brick from an axe to a knife. GREAT improvement.
Do you think this might be the route for k75 also?

NOW - another question :D
I have done the valves twice on k1100 /first checking and riding for a season - then the actual setup/ and k75 is slightly different in the chain adjuster department.
There is no hole - is the adjustor purely hydraulic type? If I loosen the chain a bit wont it 'ratchet out'? Apart from this little niggle I am all good.
One intake is .14 and ALL exhaust are just below .25 so good I have NOT believed an invoice from Germany so that the valves were checked and all in spec only 2000kms ago.

Good news is that when done the engine will sing even better than now. I was really amazed this little motor pulls 100kmh in the second gear!!!

[Laitch]

Leave the chain out of the equation; your Brick has two overhead cams, two valves per cylinder and a less complicated valve clearance adjustment. It has shim-over-bucket adjusters. A shim is seated on a land within the perimeter of the bucket. Clearance is measured using a feeler gauge. Adjustment is accomplished by replacing worn shims with shims allowing the correct clearance. There is no bucket replacement. Instructions are in the BMW K75/K100 manual downloadable from this site, in Chilton's manual and in the Haynes manual. The shim is circled in the diagram below. Instructions on video below diagram. Kawasaki shims will work. If the exhaust valves are below 0.25mm they are out of specification. They should be on the loose side of their spec. There is a hydraulic chain tensioner.

[frankenduck]

RE Tyres - in my 1100 just before selling it I have changed the tyres to Bridgestone T32 - this tyre has really transformed the brick from an axe to a knife. GREAT improvement.

There isn't a T32 size that fits the skinny rear Y-spoke wheel.

If you have a rear disc, not drum, brake you can:

A - Swap in 3-spoke wheels to run T32s. (You really only need to swap in a rear 3-spoke as the front Y-spoke will run a 110/80-18.)

B - Run Continental Trail Attack 3s on the Y-spoke wheels in 110/80-18 front and 130/80-17 rear. These are 80/20 (street/dirt) tires that are the only radials I know of that will work on the rear Y-spoke wheel.

[frankenduck]

p.s. checked the real OEM site in the morning and the input shaft FWD seal is not available in BMW anymore

Availability and pricing on RealOEM are very out of date and worthless. RealOEM is really only good for finding part numbers.

Max BMW usually has the most up to date availability and pricing:
https://shop.maxbmw.com/fiche/PartsSearch.aspx?&searchtype=undefined&parts=23121451020

[matjas]

thanks for the info guys. I was only after the tensioner. All the rest is pretty straight forward.

just to clear things up a bit - this is not the shims that wear down, are they?

The bucket replacement on the 16v series is really a major PITA - sssso happy with the 6valve shim over bucket system here :D

As per the tyres - well, the wheels are to stay. This is a classic and needs to remain one. I will see available options. The contis look good though.
So no radial tyre for K75 :(

m

[Laitch]

just to clear things up a bit - this is not the shims that wear down, are they? . . . sssso happy with the 6valve shim over bucket system here :D

The euro coin-shaped shims wear down until, for example, you need to replace them so the exhaust valve clearances are up around 0.30mm instead of below 0.25mm.

How about changing your signature from K1100LT into 1991 K75 Standard so impressionable readers here aren't led astray?

[frankenduck]

thanks for the info guys. I was only after the tensioner. All the rest is pretty straight forward.

just to clear things up a bit - this is not the shims that wear down, are they?

The bucket replacement on the 16v series is really a major PITA - sssso happy with the 6valve shim over bucket system here :D

As per the tyres - well, the wheels are to stay. This is a classic and needs to remain one. I will see available options. The contis look good though.
So no radial tyre for K75 :(

m

Those Contis I cited are radial.

[matjas]

Another thing to keep your omnipotent minds busy ;)
This shock does still have rebound damping but the bumper in it is gone.
Can this be replaced or should I go for YSS and don’t bother ?

[sooprvylyn]

Not sure if the bumper can be replaced, but if you do decide to go w another shock, give Ram Shocks a peep.  I've replaced both my K75 and K1100 shocks with them and I've been pretty happy so far. You can get info about them from contacting Realm Engineering here, and they'll get your rider weight and riding style details to get you set up with the right one for your needs.  Their site doesnt have any info on k-bike shocks, but they still make em.

https://realmengineering.com/ram-moto/

BSK used to carry them and still has some images up
https://www.bskspeedworks.co.uk/ram-rear-shocks.html

I paid £283.50(shipping to US from UK incl) in 2021 for my latest one to give an idea on pricing.  Might have gone up a little with the recent inflation.

[matjas]

with the tyres at the Polish tyre sellers I have been told it will be impossible to find the size for the Conti Trails to fit BOTH wheels.

i have been offered these:
https://allegro.pl/oferta/opony-maxxis-130-90-17-100-90-18-do-bmw-k100-k75-13209725659
and
https://allegro.pl/oferta/opona-continental-contiroadattack-3-100-90-18-100-90r18-na-przod-16545445062
https://allegro.pl/oferta/opona-continental-contigo-130-90-17-na-tyl-16593441784

however I am not into mixing tires on a bike.

Thinking also about finding the original Metzeler Lasertec in Germany maybe. These are not bad tyres and defo suit the K well.

Seems like there is not many options as it was mentioned above without replacing the wheels which I will not do.


On a side note - from the comments on the sellers account people are very happy with the maxxis m6103 promax. ALL of them are riding some old pieces of technology with no access to newer rubber.