1971 75/5 Weird Clutch / oil pump shaft break

[olironrider]

… keep thinking about your left cylinder head problem ?

Any thought about breaking down the ‘70 head’s exhaust valve to check spring height, upper/lower washers, keepers and, valve stem diameter, face, seat ?

How about the height of the pressed-in “spools” that support the rocker pivot blocks, above the face of the cover gasket surface ? If feeling “adventurous”, same look-see on the spare ‘71 head ?

Figure you already checked to see that “OT” of the flywheel agrees with TDC of piston.

/ comparison ?

If you rotate one revolution from both valve closed on TDC, do both valve show slight movement, i.e. exhaust opening and intake opening together… the cylinder is setting-up for the next fuel/air charge ?

Kind of like a “dog with a bone” here, every spare moment I’m thinking about this !

 

[pomurchu1]

… keep thinking about your left cylinder head problem ?

Any thought about breaking down the ‘70 head’s exhaust valve to check spring height, upper/lower washers, keepers and, valve stem diameter, face, seat ?

How about the height of the pressed-in “spools” that support the rocker pivot blocks, above the face of the cover gasket surface ? If feeling “adventurous”, same look-see on the spare ‘71 head ?

Figure you already checked to see that “OT” of the flywheel agrees with TDC of piston.

/ comparison ?

If you rotate one revolution from both valve closed on TDC, do both valve show slight movement, i.e. exhaust opening and intake opening together… the cylinder is setting-up for the next fuel/air charge ?

Kind of like a “dog with a bone” here, every spare moment I’m thinking about this !

Well I haven’t have had a chance to do much during the week other than realize I made a stupid mistake. Sorry for the verbose post:

I got to thinking, each rocker block has three main points that impact its setup - (1) the pushrod position, (2) the valve end position, and (3) the shaft of the rocker block aka the fulcrum.

I convinced myself that (1) was ok by measurement, and (2) was ok because I installed a sweet looking head with a great looking valve. So that just leaves (3) the fulcrum (the rocker shaft or bushing). So I came home from work, grabbed the calipers and sure enough the top block was ~2mm closer to the center of the motorcycle than the other 7 blocks on the bike. Closer inspection showed that I had somehow reversed the top block on the exhaust rocker meaning that the “built in washer” side of the block was facing in rather than out - as described in every rocker rebuild procedure there is! I reinstalled it and everything fits back in place much better.

Remember this rocker was originally from the right intake so not everything is explained here but bottom line - all valves are now tunable without being at the end of their adjustment. Anyway, lesson learned so tomorrow onto the rear main seal, pump cover, and clutch.

 

[olironrider]

Long way around the barn to just freshen the clutch

Good Work and, your investigative, measuring efforts with outstanding images… best I’ve seen in a long, long time !

All the rocker pillow blocks get their new o-ring and spacers ? The ‘71 cylinder head will leak thru that broken valve cover stud casting; may run the ‘70 head until you can get the ‘71 welded-up ?

Looking forward to seeing if any other are in the woodpile…

 

[omega man]

“Long way around the barn just to freshen the clutch”.
I think that will be a great title for when this thread becomes a “Best of Forum”.
You guys have done a great job of working your way through surprise problem after surprise problem with excellent pictures to illustrate what was going on.
Great work.
OM

 

[pomurchu1]

Short day today and another skunk although it’s one that I just introduced. Turns out that the camshaft must be from a later model airhead that used a beefier woodruff key. Therefore it wont fit the keyway on the inner oil pump rotor. I could try filing the current rotor but, as the corresponding rotor is still available, I decided to just order it.

I might put the oil pan on later today. Surely that has to go smoothly

Thanks for the help and support Olironrider and Omegaman. We'll get the skunks out one at a time.
View attachment 100136
Still waiting on the 3x spacers for the right cylinder so thats not done yet either.

 

[olironrider]

Yahno… I may have mentioned earlier about my approach to newly acquired Motorrads, most of them having been “around” over the past 50+ years; the 1971 R 75/5 was the only factory new to me: 2 980 551.

Whether, on Hope & Prayer, I ride them home (rarely) or haul them home (mostly), I go huntin’ skunks ! It has paid-off in the end and I have intimate knowledge of them; full confidence that they are Roadworthy; can establish the Periodic Maintenance Schedule.

If you can “Keep the Airhead Faith” like you’ve been doing, you too will know of what I speak ! Realize the Joy of then helping others in this Airhead Tribe of ours !

Another thought I had over the weekend: this thread also mentioned the “Otto Cycle in 4-Stroke, Internal Combustion Engines”. So when reading about TDC (Top Dead Center) or BBDC, ATDC, etc., I searched and found a simple diagram of the subject…


Thanks to testbook.com, the above diagram presents it well ! Starting at the yellow dot of the inner most green spiral, follow the spiral through the various colors to the yellow dot at the end of the grey line.

The Top Dead Center of the Compression Stroke, where we set Valve Lash (Clearance), is the junction of the black and red spiral… make sense ?

Valve Overlap, where both the Exhaust and Intake Valves are open at the same time (terminal end of grey spiral), is another area to look at for making certain the TDC/Compression (valve push rods rotate freely) has been set and not fooled by this stroke (valve push rods tight).

Flywheel markings are the reference points but you should know which cylinder is on which stroke ?

I can’t wait until you post a video of you & your 1971 R 75/5 heading down the road and, the huge smile you’ll be showing

 

[olironrider]

Kinda quiet on this thread ?

Yeh, yeh… I know: work, life, too much to do and not enough time to do it !

We’re all waiting for the next episode

 

[pomurchu1]

Well today I had a clear plate in the morning but that didn’t last too long.
I did get the right side rocker spacers/ orings on So once I get the flywheel back on I’ll gap them again for the 154th time .
Also got a new inner rotor installed on the oil pump it fit perfectly on the beefier woorduff key. If I had to do that over again I would definitely ditch the woodruff cam and get the later flat inner rotor drive. It is more robust and would mean you could remove it without touching the transmission.

Put on the new oil pump cover and o-ring and got the bolts torqued per Snowbums guidance.


Hopefully I’ll get the flywheel and clutch kit on tomorrow.

Slow going but that’s ok - it’s finally raining in California.

 

[pomurchu1]

After getting the flywheel on today I decided to hold off on the clutch installation until I verified the oil circuit was working. I should be able to see some oil from the rockers within a few seconds of the starter turning the engine.
Before doing this I tried to set the valve gap on the right cylinder now that the rocker spacers and orings were installed. Of course the right intake rocker (which was previously on the left exhaust) would not gap even at the end of its adjustment. This is just like when it was on the left exhaust.
So - I decided to install the 4 needle valve rockers I had just received from eBay. This was recommended by Ted Porter. Sure enough - all four dialed right in terms of valve gap and pushrod centering. I’ll be interested to hear how they sound but they dropped right in without any faffing around.

FYI - the pushrods look very off centered in the pics but they are really not. It’s difficult to get a representative pic.
Busy week ahead at work but hopefully I’ll get to test the oil flow some evening. Then, assuming all is well, I’ll proceed with putting everything back together.

Im assuming that it should be ok to use the starter to check for oil flow to the cylinders? If the pump works I imagine it should only be a few seconds before I see oil right?

 

[melville]

Pull the plugs and use the starter. It might take longer than you expect to see oil on all four rockers.

 

[20774]

Be sure and ground the plug threads if you remove them. You can also drop the float bowls so no gas is pulled into the engine. I agree that it takes some time for the oil to move around...my heart began to beat faster the last time I did this!!

 

[pomurchu1]

Be sure and ground the plug threads if you remove them. You can also drop the float bowls so no gas is pulled into the engine. I agree that it takes some time for the oil to move around...my heart began to beat faster the last time I did this!!

Thanks for the reminder - I would have forgotten to ground them. No need to worry about the float bowls, the carbs are sitting on the bench beside the transmission. Fingers crossed it works.

 

[pomurchu1]

I confirmed that the pump is sending oil to all 4 rockers after blocks. It took about 5 blasts of about 10 sec on the starter to see the oil. First on the right and then on the left a few sec later.

That’s a big relief!

 

[pomurchu1]

A few steps forward and backwards today
1. Installed the clutch kit and set up the freeplay/clutch arm distance. This seems like a much heavier pull than the previous clutch.
2. Installed the gearbox and added the gear oil up to the lower threads
Installed the exhaust, carbs, airbox, tank
3. Tried cranking the engine. Very labored crank with an audible squeak. Possibly from the starter.
- Wouldnt start or even get close. Spark is good.
4. Added a jumper pack to the battery - no improvement.
5. Removed the front timing cover and removed the plugs to check if the engine was giving resistance. It turned smooth as butter using an allen key in the crank/ alternator.
6 Took off the tank and starter cover and tried again. Here are the videos:
Without plugs installed:

With Plugs installed:

The squeak makes me think it might be a starter issue but this was working fine before I started this whole project. I did have it out though.
Any ideas or things to check?

 

[pomurchu1]

Rather than leave this thread hanging I'll keep updating until I get out on the road again.

1. Regarding the starting problem I was using jumper cables to connect the battery to the hot and ground on the bike in the video above. In the end I decided I would just try it withe the battery installed as normal - it fired right up. I guess I just wasnt able to get enough current to the starter with the jumper cables in the loop.

2. I got the transmission back on and the clutch set up. The clutch pull seems a lot harder than before but i suppse thats to be expected with a new spring.

3a. I installed the shaft drive and final drive and decided to change the gear oil. No problem with the final drive. However I removed the shaft drain plug and filler plug and nothing more than a brown stain dropped out of it. It was bone dry practically. I found that the shaft/transmission boot was leaking so I replaced that (what a pain).

3b However the really bad news is that the threads for the shaft drive drain and fill were really buggered up beyond reliable use. I decided to separate the shaft and the final drive to check the condition of the gear - thankfully they looked great but there was bits of thread all over the place.

So - thats where I am now. To repair the threads I will need to remove the threaded ring as it interferes with the bottom of the drain and fill plug holes. I havent decided if I will take the assembly to a machine shop to get the Time-serts installed or if I will get the kit to do it myself. Unfortunately Ted Porters Beamershop doesnt do component work any more - If they did I would just drop it off there as i live very close.

I also dont have the special tools. I took an angle grinder to a piece of scrap steel and made a crude gear holder to get the gear holder nut off, but looking at the threaded ring I will need something less crude. The walls of the threaded ring look very flimzy so I'm afraid I would damage it if I tried to bodge something together.

Anyway - getting closer but there is still a few skunks coming out of the woodpile as Oldiron (Don) has been saying.

 

[olironrider]

Buy a ‘71 R 75/5 and get a free herd of skunks

Oh… I feel your pain, Paul ! Great to hear you’ve not given up on the… er, what have you named the R 75/5: “Skunk Works” ? I mean, it’s black with white coach lining after all

There is “danger close” in attempting recoup of those stripped out driveshaft fill & drain ports (have you checked the fill & drain ports of the rear drive ?) ! The pinion with its bearing package, is heat-skunk, er, SHRUNK in the housing ! Along with the bearing pack, there are seals, shims and sealant involved !

Send it out for repair !

Maybe Ted Porter can recommend a shop in So-Cal or, contact the So-Cal Airheads Airmarshal: Gary Jackson in San Diego, socalairmarshal@gmail.com… If you’re not an Airheads Beemer Club member, become one today ! There might be some ‘Hedz nearby that will help you with your bike… “misery loves company” ? Living in the Wilds of Pennsylvanistan, I use either a great local independent shop or, MAXBMW; they’ve got the special tooling, presses, precision measuring, heating oven, experience. I know when to call in a ‘9-Line’ for hot extraction.

Over the decades I’ve worked on these air-heads, the three (3) consistent issues I find are: under-lubricated, over-torqued, mal-adjusted.

Hoping you noticed that the M8-1.25 studs connecting the rear drive to the driveshaft housing (with gasket), have reduced wrenching flats on the nut, unlike a standard M8 nut ? Close quarters there (recommend 350 IN/LB Tq), with the rear axle fully installed through the swing arm and rear drive, for alignment purposes.

The short wheelbase 80/90 gear oil fill of the rear drive/driveshaft assembly after complete drain, is a measured: 125ml.; fill & drain plugs torqued to recommended: 120 IN/LB with fresh crush washer. Recommended torque on rear drive is: 170 IN/LB FILL, 240 IN/LB DRAIN, with fresh crush washers; of course, 80/90 gear oil fill to lowest thread of oil fill port with bike on center stand.

I seem to remember you knowing of the 12 point bolts securing the driveshaft to the transmission output flange, are to be the shorter ones without lock washers but, with blue LOCTITE ?

Perhaps, you might give a “shout-out” as to where you’re looking for the next skunk so, we here can offer advice before things really smell bad

Paul, I am truly impressed with your valor in this seemingly relentless skunk hunt; so looking forward to your video of the First Ride !

Don

 

[88bmwjeff]

If you're in CA and decide to send it out for repair, one option is Scottie's Workshop.

https://blog.scottiesharpe.com/

 

[pomurchu1]

Send it out for repair !

Yes - I’m leaning that way. I have done time-sert repairs before but that was a long time ago with all the right tools on hand.

Maybe Ted Porter can recommend a shop in So-Cal or, contact the So-Cal Airheads Airmarshal: Gary Jackson in San Diego, socalairmarshal@gmail.com… If you’re not an Airheads Beemer Club member, become one today ! There might be some ‘Hedz nearby that will help you with your bike… “misery loves company” ?

I’ll check with Ted if there is someone in the immediate vicinity.
I’ve been a MOA member for about 3 years.
Regarding that special tool to remove the pinion ring apparently this works too for a whole lot less money https://a.co/d/cxh27iF

I seem to remember you knowing of the 12 point bolts securing the driveshaft to the transmission output flange, are to be the shorter ones without lock washers but, with blue LOCTITE ?

Yes- all good there. Full confession - I didn't use a torque wrench so I gave them a good grunt. I will recheck them at the next oil change to make sure.

Perhaps, you might give a “shout-out” as to where you’re looking for the next skunk so, we here can offer advice before things really smell bad

Will do. Although the only skunk I looked for was the clutch repair. The rest of them just showed up

Paul, I am truly impressed with your valor in this seemingly relentless skunk hunt; so looking forward to your video of the First Ride !

Don

Yep. Hopefully soon. Actually none of the issues have been too bad really. With the great help and advice from yourself and others on here the issues were fairly manageable. If I send the rear drive out I'll just focus on timing and and maybe see what impact (if any) that scratch on the left cylinder wall is having.

Paul

 

[pomurchu1]

If you're in CA and decide to send it out for repair, one option is Scottie's Workshop.

https://blog.scottiesharpe.com/

Thanks! I’ll check this out. I’m in the Santa Cruz area.

 

[olironrider]

… an excellent plan, Paul !

The Airhead Beemers Club is dedicated just to the 1970 - 1995 air-cooled BMW Motorrads: airheads.org

Here’s the February 2025 cover…



All about Airheads: the folks that love them, technical support, member sponsored get together TechDays in your area, folks that’ll teach you how to maintain them. Twelve issues a year, big event in PA on the Super Bowl weekend, “SuperTech” with seminars, cut-away components that so you can see how they work… decades of my membership with the ABC !

Myself, I’m a Life Member of the BMW Motorcycle Owners of America, which covers them all.

Together, ABC & MOA, my BMW Motorrad world is complete

Don, ABC 6344, MOA 95089