R75/6 carbs vs /7

User avatar
schrader7032
Posts: 7193
Joined: Fri Oct 27, 2006 3:00 am

Re: R75/6 carbs vs /7

Post by schrader7032 »

I would certainly retorque at say 100 miles (or sooner) and again at 500 as you suggest. If you don't see anything changing then maybe the duration can be extended. Use 25 ft-lbs...no need to go any higher than that.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

Andey
Posts: 44
Joined: Wed Sep 02, 2020 12:45 am

Re: R75/6 carbs vs /7

Post by Andey »

About to change the main rear seal, so will re-torque everything after it’s done...

Hopefully I can get it back on the road soon

User avatar
schrader7032
Posts: 7193
Joined: Fri Oct 27, 2006 3:00 am

Re: R75/6 carbs vs /7

Post by schrader7032 »

Just to remind in case you weren't aware...to get to the rear main seal, you have to remove the flywheel. You need to block the crank in the front of the engine so it doesn't move forward during the seal change. Snowbum has some discussion of that here:

https://bmwmotorcycletech.info/flywheel ... arning.htm
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

srankin
Posts: 78
Joined: Fri Jul 14, 2017 8:45 pm

Re: R75/6 carbs vs /7

Post by srankin »

I concur with Kurt on blocking the crank, nasty things can happen if it moves and the shim comes off its pins.

I would also suggest purchasing a tool to install the seal as well. I found this one on Boxer 2 Valve and Siebenrock also carries it.https://www.boxer2valve.com/rear-cranks ... -tool.html

The seal should be soaked in oil for a bit and it must be installed straight and to the proper depth. a tool like this makes it a whole lot easier to install.

Now mind you, I have never installed a main seal without the proper tool. In fact, I have used the BMW tool. getting the big seal in straight and proper is tricky, if it goes in wrong and you have to pull it back out, you have pretty much ruined it.

Believe it or not yesterday I was at my friend's shop and he had just replaced a main seal which the bikes owner had installed a few months before only to have it leak. The problem turned out that the bikes owner had used some kind of punch or rod to tap the seal in place by going around it. He had damaged it and so it leaked.

I am sure, the seal can be changed without the tool if care is used. Something else can be substituted.

While you have the flywheel off, it would be a good idea to also change the seal on the oil pump as well. One of my friends bought a bike where the previous owner had changed the main seal and when Jim bought the bike six months later, the pump seal started leaking.

Good luck with the job. St.

Andey
Posts: 44
Joined: Wed Sep 02, 2020 12:45 am

Re: R75/6 carbs vs /7

Post by Andey »

Would be the first time attempting to replace the main seal... so did a bunch of research before hand... the usual YouTube and the same web resources to walk through the methods before attempting it.

I managed to track down a second crankcase when I was in LA earlier this year (its a long story...)... and the seller did mention about the crank shim even though I told him about knowing absolutely nothing about what he was talking about... so that stuck with me, I was conscious to figuring out the significance...

I ended up using the boxer2valve method of using a cargo strap and a hex socket to make sure it didn’t budge...

Seemed to work ok, was nervous though and took care to make sure no forces were forward on the crank...

The main seal seems to be the original, white with BMW written on it... and replaced the oil pump cover o-ring too...

I managed to get a machine shop to create 2 tools... 1, a flat 100mm disc to push the main seal in place using the old flywheel bolts and 1, to pull the flywheel out (basically a flat metal bar with 2 elongated holes using the clutch release tool...) so glad I got that made as the flywheel wouldn’t come out by hand..)

The clutch friction plate was gone... no material left and has some small cracks in it...

I’m still to torque down the clutch, but slow progress on getting it back together...
Attachments
73EA0B6C-DECC-4D9C-9035-CD533F2CC700.jpeg
0E2A8BD7-C5BD-43D0-AD1C-2E29AB03D88B.jpeg
ACE1CAD8-98C5-469C-8648-38417FBAD96B.jpeg

srankin
Posts: 78
Joined: Fri Jul 14, 2017 8:45 pm

Re: R75/6 carbs vs /7

Post by srankin »

Give yourself a pat on the back for researching how to change the seal and for having the tool made for its proper installation.

I am amazed at the number of videos on the internet now compared to 10 or so years ago. Cheers, St.

Andey
Posts: 44
Joined: Wed Sep 02, 2020 12:45 am

Re: R75/6 carbs vs /7

Post by Andey »

I’m completely indebted to all who has posted any information online.

Including the gents posting on this forum.

Couldn’t have achieved much without it.

The drive train bolts are no fun at all... and had to eyeball the torque values of the bolts... not the most user friendly design there...

Also, in retrospect I should have changed the pressure plate too... I feel like that will come back to haunt me... will be another breakdown practice session ;)

Onto the final parts of getting the bike restarted...

srankin
Posts: 78
Joined: Fri Jul 14, 2017 8:45 pm

Re: R75/6 carbs vs /7

Post by srankin »

Always remember, any car or motorcycle company designs and builds things in order to make them cheap to sell high. Make it easy to assemble on the line, again easy is cheap. The poor guys who have to work on them are the last guys to find out how things go together and too bad for them, LOL.

I have a friend who was a mechanic on cars for 35 years, he has a tool box full of weird, bendy, strange, special tools needed to remove various fasteners on different makes of cars.

I watched the BMW documentary about the motorcycle plant. I forget exactly how long it takes them to assemble from a collection of parts to a complete S1000. I think it is something like 20 minutes? Of course we know if the head gasket needs changed later on, it will most likely take three hours to do the job.

When I am confronted with a bolt or screw hidden just out of sight, or difficult to remove, I turn the air about me blue, then remember or think about how the bike was assembled and in what order it was assembled. That doesn't make things better but, I makes sense.

Cheers, St.

Andey
Posts: 44
Joined: Wed Sep 02, 2020 12:45 am

Re: R75/6 carbs vs /7

Post by Andey »

srankin wrote:
Wed Sep 16, 2020 8:13 am
Always remember, any car or motorcycle company designs and builds things in order to make them cheap to sell high. Make it easy to assemble on the line, again easy is cheap. The poor guys who have to work on them are the last guys to find out how things go together and too bad for them, LOL.

I have a friend who was a mechanic on cars for 35 years, he has a tool box full of weird, bendy, strange, special tools needed to remove various fasteners on different makes of cars.

I watched the BMW documentary about the motorcycle plant. I forget exactly how long it takes them to assemble from a collection of parts to a complete S1000. I think it is something like 20 minutes? Of course we know if the head gasket needs changed later on, it will most likely take three hours to do the job.

When I am confronted with a bolt or screw hidden just out of sight, or difficult to remove, I turn the air about me blue, then remember or think about how the bike was assembled and in what order it was assembled. That doesn't make things better but, I makes sense.

Cheers, St.
Definitely relating to that... takes the assembly line with the right space and setup 5 mins, takes the weekend warrior 3 hours...

Funny that

srankin
Posts: 78
Joined: Fri Jul 14, 2017 8:45 pm

Re: R75/6 carbs vs /7

Post by srankin »

Not ha ha funny either, LOL.

If you get the chance on Y tube see if you can find the documentary I am writing about, it is really quite something to watch.
St.

Post Reply