K75 Noises

[bluebossa]

Hey again folks...

Thanks in advance - would appreciate your wisdom on what to look for first?

[Laitch]

It would be helpful for you to make a video containing the noise with all its permutations during idling and moderate revving, post the video on YouTube as public, and then post the link here. In my opinion, it's too early to focus on the timing assembly although it's a possibility. When somebody indicates a loud rattle, the alternator rubber dampers are my first consideration and relatively easy to rule out. Faulty fuel injectors would be next.

[TriSpark]

The cam chain rattle diagnosis sounds like a guess from a mechanic who hasn't much experience of K bikes, and that's not unusual as they don't see them on the work bench as often as they used to. 48K miles.....my K75 has 120K and no trace of any cam chain noise at all. When I lived in London I had a plain K100 with 80K on it, and no cam chain noise on that either.

One thing I've learned here is to always follow Laitch's advice before tearing into the engine. Let us know how you get on.

[Laitch]

That's a useful video. I recommend anybody with a mysterious noise post something like that for group diagnosis.

I used a strap wrench to anchor that cup for removal. Use Liquid Wrench, Kroll or PB Blaster on the nut and screw. After spraying, tap the nut and screw joint a few times—without deforming either—then let them sit for fifteen minutes or so before disassembly. This is my usual procedure on fasteners that likely haven't been touched for years. Regardless of what you choose to do, they should release each other without putting you through a dying strain on the end of the wrench. If they do, regroup, heat up the fasteners with a heat gun, apply the penetrant until you're smoked out of the room, have a coffee then try again.

It looks like you've got things under control. Wipe the dampers with silicone grease so they'll stick into position. Align the arrow so the paddles will index correctly into the damper joint spaces.

[TriSpark]

Good video and photos - thanks for sharing those, I learned something new about Bricks from that. I viewed the video, and it's clear the knocking noise is at the back of the engine, nowhere near the cam chain. With the rubber dampers being 40 years old, it's no surprise they have crumbled and failed. Better check mine.......I had the starter motor seize up on my K75 due to old age, so I hope my alternator is not going to go next.

Much better than tearing the engine apart only to find the cam chain is just fine, right?

You've got a nice looking K75 there.

[Laitch]

Its a lovely Bike - weird that Naked T with RT bars, but maybe they switched to that for the later models... My C bars are lower...

The higher bar is the original equipment—T meaning touring. From what i've read it was a dealer-installed limited edition. The same bar is OEM on the RT and the Standard. My Standard had it plus an aftermarket National full windscreen. After 10K miles, I removed RT bar and windscreen to install a C-bar. I also sold the Corbin Canyon seat with its backrest at that time. I returned to an OEM bench but the custom padding within it is honeycombed. Its profile allows me to shift my butt fore and aft according to riding conditions and it's comfortable on hours-long rides unlike my experience with the OEM.

After 5K more miles I removed the C-bar to install a sidecar bar. The sidecar bar is as low as an S-bar but is wider and has less pull-back. After decades of bicycling thousands of miles with dropbars on touring bikes and straight bars on mountain bikes, the sidecar bar gave me a comfortable and familiar riding posture while lessening wind drag on my body and allowing my butt and thighs instead of my back to absorb any excess road shock. The Brick is still as black as in the top photo; it had a case of the blues the day it was photoed.

[bluebossa]

Here's another little puzzle I'd like help with - Centre Stands..

Were there different versions of the centre stand RT / S / C / T?
this might explain why is my 1986 K75C is now so hard to get on its stand...

My C might now have a centre stand from an RT, though I thought it was from an S, as the drivetrain I put on was an S - though the orginal Bike it came off was an RT, I know all very confusing- are RT stands taller? The C now sits 4/5 inches off the ground at the back, it does have the 17 inch wheel now, whereas originally it had the 18 inch Drum brake wheel, I initially thought it was just that, but several near hernias later, I'm not so sure.

Pics for comparison - 1st two are 1994 K75T with original stand, see height - second 2 is 1986 K75C with what I think is an RT stand, see how high it sits
I just assumed that centre stands were all the same!

I think I still have the C stand - the 1994 is a dream to put on its centre stand, while the 86 now gives me a near hernia everytime!

I tried jacking the Bike today, but didn't find a way to get it high enough without losing all stability to try and swop them over - I have an Engine Jack flat plate type - any tips on how to change the Stands without taking the whole back end off?

[Laitch]

Whenever I want to know if one particular part is the same on different models, I use a parts fiche. If the numbers are the same, the parts are the same.

According to Max BMW's parts fiche, the Standard, the S, the T, the RS and the RT 2V models all have the same stands and brackets. Measuring them would confirm that. However, sometimes a 4V side stand has been installed when the original hollow tube 2V stands have been deformed or broken by the effects of internal rust. Yours is not 4V stand. An 18" wheel definitely makes the lift easier because the mass you're moving is already raised by a half-inch and the angle of the lift has been modified favorably. A tire with an 80 aspect ratio requires somewhat more effort because the mass is lower than when carried by a tire with a 90 ratio and the angle of the lift also has been altered.

Lubing the stand pivot is of utmost importance to lessen effort. Dried grease—or no grease—makes lifting exponentially more difficult. I lube the stand whenever I sense more effort in a lift. It could be necessary to disassemble the stand to inspect and clean its pivot pin and bushing.

If you had years of lifting that Brick onto a stand when it had an 18'' rear wheel, your body's muscle memory hasn't adapted to the difference yet but it will. Verify the front wheel is aligned during the lift. Misalignment will increase friction resulting in more effort.

[daveson]

I tried jacking the Bike today, but didn't find a way to get it high enough without losing all stability to try and swop them over - I have an Engine Jack flat plate type - any tips on how to change the Stands without taking the whole back end off?

With the centre stand up instead of deployed, lean the bike against a wall, in some sort of stable way, for example with the front wheel chocked in a channel,  then remove the stand assembly.

It might be good to take some measurements first, like stand heights and angles, frame height, centre to centre measurements for the suspension.

.

[bluebossa]

Whenever I want to know if one particular part is the same on different models, I use a parts fiche. If the numbers are the same, the parts are the same.

According to Max BMW's parts fiche, the Standard, the S, the T, the RS and the RT 2V models all have the same stands and brackets. Measuring them would confirm that. However, sometimes a 4V side stand has been installed when the original hollow tube 2V stands have been deformed or broken by the effects of internal rust. Yours is not 4V stand. An 18" wheel definitely makes the lift easier because the mass you're moving is already raised by a half-inch and the angle of the lift has been modified favorably. A tire with an 80 aspect ratio requires somewhat more effort because the mass is lower than when carried by a tire with a 90 ratio and the angle of the lift also has been altered.

Lubing the stand pivot is of utmost importance to lessen effort. Dried grease—or no grease—makes lifting exponentially more difficult. I lube the stand whenever I sense more effort in a lift. It could be necessary to disassemble the stand to inspect and clean its pivot pin and bushing.

If you had years of lifting that Brick onto a stand when it had an 18'' rear wheel, your body's muscle memory hasn't adapted to the difference yet but it will. Verify the front wheel is aligned during the lift. Misalignment will increase friction resulting in more effort.

Thanks Laitch - Mystery Solved - it was the Rear Shock, nothing to do with the stand.
I fitted a Sachs to the C from the previous build - it was 50mm shorter than the T shock (which is a YSS at 350mm)
I thought the Yellow sprung Sachs was an upgrade, but didn't consider its length - and it was wound up tight... still is... !

So, last night I fitted a normal length, bolt to bolt 350mm Koni shock, from a parts Bike which transformed the Stand experience... its always the simple things

Picture attached but way easier now and the C is sitting properly again now...

All stands are the same as you say and I like you defer to the MAXBMW Fiche when I'm confused for part numbers and compatibility...

[Laitch]

 Good find!

[Edward]

no wonder it was hard to place on the stand. The difference in length could have blown out your knee.

[bluebossa]

Nearly did, you are 100% right on that... crazy hard...