1976 R75/6 - Clutch Adjustment

[b25bsaboy]

Good afternoon,

I am in the process of adjusting my new clutch cable on my 76 R75/6. Just watched the YouTube of Chris harris and he does it with an 8" long coat hanger wire that butts up to the back of the transmission that attach's to the engine casing. Went and did this, but found that the coat hanger wire, there is about 1/4 - 1/2" that goes past the clutch cable arm. Everything is slack, meaning that the clutch lever has about a 1/2" end play.

Would someone give me some direction and guidance or have I missed something?

 

[20774]

I think I saw Chris' video on that and I think he went over it pretty quickly...possibly skipped some important steps...basically his approach and "tool" is correct but in the link I pulled from the Resources thread, the distance is exactly 201mm per Tom Cutter...that's really 7.9 inches.

http://forums.bmwmoa.org/showthread...-in-Clutch-rod&p=499945&viewfull=1#post499945

Part of the adjustment is to the lever at the back of the transmission...it needs adjustment too.

Follow the above to the letter and hopefully it will work out better. If not, let us know.

 

[dennisdarrow]

Another method, with all due respect towards the discussed; but I stay with my owner's manuals for every air cooled BMW that I have ever owned.............Adjust the free play so that ones has 2mm of slack for the gap at the lever and 5mm of slack down at the clutch lever behind the transmission........I know that Kurt and I go round and round about this; but to each what has worked for them..........God bless.......Dennis

 

[PGlaves]

When you disect the factory recommended method to really understand it, it is simple.

Step one - adjusting the cable to a fixed length at the rear is to set the lever arm in a position so that in its travel through its arc it is as parallel to the back of the transmission as optimal. This minimizes side stresses on the throwout bearing and the clutch rod.

Step two - adjust the adjuster on the transmission lever arm to set free play.

 

[20774]

Step one - adjusting the cable to a fixed length at the rear is to set the lever arm in a position so that in its travel through its arc it is as parallel to the back of the transmission as optimal. This minimizes side stresses on the throwout bearing and the clutch rod.

Step two - adjust the adjuster on the transmission lever arm to set free play.

What finally made sense to me is which end of the cable you use to make these adjustments.

For Step One, you use the handlebar adjuster...this is where you set the 201mm.

For Step Two, you use the adjuster on the lever at the back of the transmission...this sets the free play at the handlebar lever.

 

[lmo1131]

Went and did this, but found that the coat hanger wire, there is about 1/4 - 1/2" that goes past the clutch cable arm.

If the 201mm [7.91"] guage (aka: coat hanger wire) extends 1/4 - 1-1/2" past the end of the throw out arm, the 6mm bolt (#10) is bearing down on the piston (#5), which in turn, is bearing on the rod (#1), preventing the throw out arm from rotating back any further. Chris mentioned this in the video.

Loosen the 6mm lock nut, and back out the 6mm bolt.

BTW, the throw out arm in the diagram above is drawn incorrectly... the pivot pin does not pass through the center of the 6mm bolt. If the arm were configured the way the drawing indicates, the pivot would have to be supported from either side. And even if it were, there wouldn't be enough travel to move the piston.

There must be an offset, between the 6mm bolt, and the pivot pin, and there is ... as seen in the photo. I can't believe this drawing detail error has existed for 40+ years.

 

[20774]

Lew -

I've often heard Tom Cutter say the diagrams are not actual parts drawings and only vaguely give reference information. If you were to build the bike from the diagrams, you might have a non-functioning bike!

I was thinking about your statement that the #10 bolt was bearing on the piston. My vision is that the handlebar knurled knob needs to be loosened to allow the lower end of the transmission lever arm to move towards the rear of the bike to get to the 201mm distance...the #10 bolt has nothing to do with that. Once you set the distance with the handlebar adjuster, you then turn the #10 bolt in/out so that you have freeplay at the hand lever. I think the Haynes/Clymers might say that you need to adjust the #10 bolt so that if you push on the lower extremity of the transmission lever, it will move forward about 5mm or so until you feel the resistance...this is the freeplay that you should have so that the bearing of the clutch rod stackup is not turning all the time.

Am I seeing it wrong?

 

[lmo1131]

Everything is slack, meaning that the clutch lever has about a 1/2" end play.

found that the coat hanger wire, there is about 1/4 - 1/2" that goes past the clutch cable arm.

Kurt, like you guys, I've adjusted my clutch many times using this method. The results are always rewarded with smoother shifts.

With slack as stated above, here's what I think Rick is describing.

If this is the case, that the wire gauge extends past the bottom of the clutch arm (see my sketch), then the bottom of the clutch arm needs to rotate toward the back, not (as we usually see) toward the the front.

But I messed up in my previous description, the only way to accomplish this is by running the bolt IN, not out. The pivot is above the bolt; so running the bolt in will move the bottom of the arm toward the rear of the bike.

But I can't think of how this condition could exist, and still have functioning clutch...

Do I understand the condition correctly Rick?

 

[20774]

Lew -

That will work. The only thing that one needs to be careful of is where the amount of threads are. You have many more threads to work with up at the handlebar versus down at the clutch lever bolt. That's why (I suspect) Tom says to use the handlebar to eat up that 1/4-1/2" and then fine tune the amount of freeplay with the clutch lever bolt.

As has been pointed out, it will work both ways, but if you run out of adjustment, consider what can be done to bring the adjustment back within the range of threads.

 

[lmo1131]

I totally agree Kurt. I'm just trying to understand how the condition I sketched can occur.

As I mentioned, I've adjusted my clutch many times over the years, but have never encountered the condition (as sketched, and IF that is what Rick is dealing with).

In my experience, it's always that that the throw-out arm needs to be adjusted forward, as per Chris' video.

edit_

I just re-read Rick's post, he mentions adjusting his new clutch cable.... . if he does not have the correct cable, i.e., a shorter cable, this condition might occur (?).

 

[20774]

New cable could be an issue...as in not the right one...but it still might be adjustable. If the OP didn't put the handlebar lever knurled adjuster at sort of mid range on the threads, then something like your sketch could result.

As I was out for my ride, I mulled over the following:

-- the link I provide contained the steps that were taught at BMW tech school (eg, Tom Cutter)

-- 3 things need to be accomplished:

1) when the handlebar lever is completely out, the tranny lever must not be resting against the rear frame member
2) when the handlebar lever is at mid-pull, the tranny lever should be parallel to the back plane of the transmission and/or the cable and the tranny lever make a 90 degree angle
3) there must be some freeplay so that a) when the handlebar lever is completely let out, there is no pressure on the clutch rod bearing...ie, the clutch is fully engaged and b) when the handlebar lever is fully pulled in (ie, in the process of shifting gears), the clutch must be full disengaged. Typicaally 5-6mm of freeplay should be about right. You don't want so much freeplay such that you spend those precious fractions of a second taking up the slack before you finally get clutch action...you want it to be essentially "right there".

However you get it done, those are the results you finally need!

 

[b25bsaboy]

Good afternoon,

I am in the process of adjusting my new clutch cable on my 76 R75/6. Just watched the YouTube of Chris harris and he does it with an 8" long coat hanger wire that butts up to the back of the transmission that attach's to the engine casing. Went and did this, but found that the coat hanger wire, there is about 1/4 - 1/2" that goes past the clutch cable arm. Everything is slack, meaning that the clutch lever has about a 1/2" end play.

Would someone give me some direction and guidance or have I missed something?

My apologies in not responding sooner, as it just seems since I've retired, I am always running out of time for one reason or the other.

Here is what I know and I think the solution is simple, but will not know till I remove the new clutch cable and compare with the old one that I kept. I agree with Kurt, Lew, Dennis and Paul. Once I have established what the exact cable length is, will go to the next step and start doing the fine adjusting both at the handle bars and at the clutch lever at the back of the transmission.

Note for Lew with regards to his drawing, in that it looks pretty accurate to me and you are correct in where the space distance arrows are.

 

[b25bsaboy]

Good afternoon,

I am in the process of adjusting my new clutch cable on my 76 R75/6. Just watched the YouTube of Chris harris and he does it with an 8" long coat hanger wire that butts up to the back of the transmission that attach's to the engine casing. Went and did this, but found that the coat hanger wire, there is about 1/4 - 1/2" that goes past the clutch cable arm. Everything is slack, meaning that the clutch lever has about a 1/2" end play.

Would someone give me some direction and guidance or have I missed something?

Finally was in the shop and removed the new clutch cable. Placed it on the work bench , laid out the old clutch cable and between the old and the new it is about 1 1/2" difference between the old and the new (older one being longer). Re-installed the new cable and paid attention to the routing, meaning did not put it up through the gusset that holds the VIN plate. Backed the adjustment bolt at the transmission and made sure that there was plenty of slack at the clutch lever. Took the 8" coat hanger length that Chris Harris talks about in his video about adjusting the clutch cable. It now pretty much aligns that the end of the rod is perpendicular at the ferrel on the lever. Went and started the adjustment with the handle bar lever having a 1/16" play when the clutch lever is pulled before it engages the transmission lever arm.

When I get the R75/6 started, I will know better if its right when the clutch lever is pulled and I engage first gear if it's correct.

Thank you to all the responded to my question.

 

[henzilla]

Here's another option to throw into clutch adjustments.

I added one when I replaced the original /6 cable. Sure makes the lever feel like a modern hydraulic with an even easier feel. Some folks may freak out having to CUT the cable however

http://benchmarkworks.com/articles/howto/clutch.html

 

[lmo1131]

1/16" play when the clutch lever is pulled before it engages the transmission lever arm.

If I read/understand this correctly you have only 1/16" free-play measured at the handlebar perch/lever?

When finally adjusted you want to make sure you have a 5mm gap (+/-) between the clutch lever and the perch to ensure that you have sufficient "free play". 1/16" is barely any, and even resting your fingers on the clutch lever might cause the throw out bearing to exert pressure on the clutch. Not good.

5mm isn't going to increase your reaction time measurably.

 

[b25bsaboy]

If I read/understand this correctly you have only 1/16" free-play measured at the handlebar perch/lever?

When finally adjusted you want to make sure you have a 5mm gap (+/-) between the clutch lever and the perch to ensure that you have sufficient "free play". 1/16" is barely any, and even resting your fingers on the clutch lever might cause the throw out bearing to exert pressure on the clutch. Not good.

5mm isn't going to increase your reaction time measurably.

Morning Lew,

Went and checked and its very close to the 5mm (+/-) gap before it engages in the arm at the transmission being pulled. Thank you for your wisdom and guidance.