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1973 R75/5 Back-to-road Project

Springs

You could also go for the BMW sport springs with part number ending in 017. They are actually shorter than the stock springs, making them easier to install. They're made out of a heavier gauge wire. The soft springs probably have a dab of yellow paint on the end. The sport springs have white paint.
I've had a sort of problem with the Progressive springs in that they tend to bind. Also, they come with spacers that are not really needed and make them a bear to install.
 
You could also go for the BMW sport springs with part number ending in 017. They are actually shorter than the stock springs, making them easier to install. They're made out of a heavier gauge wire. The soft springs probably have a dab of yellow paint on the end. The sport springs have white paint.
I've had a sort of problem with the Progressive springs in that they tend to bind. Also, they come with spacers that are not really needed and make them a bear to install.

Thanks, I'll keep that in mind for when I get there!
 
Right carb leaking oil....yes oil.

Yes oil, not gas. It definitely is engine oil and I assume it comes through the breather hose which is stuck in the right carb.

I noticed a few drops of oil on my boot after a 30 mls "spirited" test ride (most of the time around 65 mph or a bit faster). First I thought I overfilled my engine oil but oil level is spot on, about 10% under max.

Is this normal? My Harley with the Evolution engine did it sometimes out of the airfilter, but only after hard rides.
 
Can be normal. You want to make sure the breather spout is so positioned that it does not touch the air flow tube in order to reduce the tendency for the oil vapor to condense rather than be drawn into the intake as vapor.
 
... probably have a dab of yellow paint on the end. The sport springs have white paint..

Just rebuilt my forks also and couldn’t find reference (that I know I have found before) on if painted end of spring was top or bottom? My recollection was that the painted end goes on top so that is how I installed them. Can anyone confirm this? Thanks.
 
The part of the spring with the tighter windings needs to be put at the top. Theoretically, that reduces the unsprung weight which consists of the wheel, brakes, and the lower part of the spring. But the weight difference is virtually unnoticed, so the key would be just to be consistent in the spring orientation.
 
Can be normal. You want to make sure the breather spout is so positioned that it does not touch the air flow tube in order to reduce the tendency for the oil vapor to condense rather than be drawn into the intake as vapor.

Good advice thanks, need to double check, since I had the air filter housing out for cleaning.
 
Back to the dreaded stud....

There is a tool shown on page 20 of the September 2017 Airmail. hpd_online.com/stud_tool.asp High Precision Devices Inc,Boulder Colorado USA .

While I have been able to put 200 mls on my bike, the noise on the right cylinder has become louder, so I took off the valve cover to take a look. Rocker arm end play on the exhaust side was huge and as expected the upper right head bolt was lose (not totally but 10-15 ft.lbs max).

I took the rocker arm off, double nutted the stud and turned it in a bit further than the other ones in hopes of grabbing a thread down there but no success. At around 18 ft.lbs I started pulling out the stud.

I did a lot of reading over the last days, and I am leaning towards buying the tool from HPD as suggested by James (and others I have talked to). Yes, it's expensive, but I called HPD and I like that they are using an insert (which is supposedly better than a helicoil) and they also include the guide to drill the oil passage.

Now my question is, can you tell from my engine number (4000410) whether my engine has the 99 mm or 97 mm bore? Right now they offer the tool only for the 99 mm, but they can fabricate an adapter ring. The more I think about it it, the more I want to do it myself...Thanks!
 
...Now my question is, can you tell from my engine number (4000410) whether my engine has the 99 mm or 97 mm bore? Right now they offer the tool only for the 99 mm, but they can fabricate an adapter ring. The more I think about it it, the more I want to do it myself...Thanks!

I'm sure someone will come along and tell you definitively, but if I remember what I read correctly, the bore size changed in 1976?
 
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You VIN is a January 1973 build and is way before the spigot sized changed (should be the '76 /6 models) so your size is 97mm.
 
Hey guys, maybe we might create a registry of members who own airhead special tools, who might be willing to participate in sort of lend/lease program. I, for one, am wiling to loan these sort of things to members. Something to consider.
 
Hey guys, maybe we might create a registry of members who own airhead special tools, who might be willing to participate in sort of lend/lease program. I, for one, am wiling to loan these sort of things to members. Something to consider.

Love the idea!
 
Congrats Olaf - nice ride - I used POR to recondition tank on my airhead.

You'll more like than likely Ned to buy carb kits from Bing - have you sought out the local airheads club in TX? A great way to learn how to repair, tune and gain appreciation for this wonderful air cooled bike.

Pretty!

I restored the exact same bike but yours looks very clean! One thing I like is that the original rear shocks are on it and not rusty! It is hard to find OEM parts for that.
Have fun! That Guppie tank is rare. Plus it is the first year that BMW did the extended drive shaft mod and you can see the weld seams. Very cool!



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Ok everyone wish me luck. The drill rig arrived in the mail today, cylinder is off and I am ready to re-thread the stud. I ended up renting the tool from Northwood Airheads, looks solid, so I will go the heli-coil route. I also talked to HPD, they would make me a 97mm tool for the same price they sell the 99mm tool for, but I decided to rent for now and not to spend the big bucks. All in the hope I won’t have to do this again! I‘ll post some pics how it goes.


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Successfully cut the thread. The two pics show the newly threaded hole without and with the heli -coil. Now comes the assembly!

cb384b577d4da314b4bace2a37d7ab62.png


b8e1d1faae3716029fb386c71f21dfc6.png



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Cylinder stud successfully re-threaded!

As mentioned in my previous post, all went well. I already put 100 mls on the bike and re-torques the heads. All is fine a no leaks.

I decided to start a website where I will keep track of major maintenance and repair projects. Check it out: www.r75slash5.com

By the way, the next project is lined up, I ordered new fork springs. I will also have to do my steering bearings pretty soon. One thing after another though....
 
As mentioned in my previous post, all went well. I already put 100 mls on the bike and re-torques the heads. All is fine a no leaks.

I decided to start a website where I will keep track of major maintenance and repair projects. Check it out: www.r75slash5.com

By the way, the next project is lined up, I ordered new fork springs. I will also have to do my steering bearings pretty soon. One thing after another though....

You may find this set of write-ups I wrote when I rebuilt a 1973 R75/5 helpful.

--> http://brook.reams.me/bmw-motorcyle-rebuilds/1973-bmw-r755-rebuild-project/

At the end is an index to all the documentation organized by the part fiche subsystem number (11 Engine, 12 Engine Electrics, etc) There are other articles on my site that may also be of interest to you, so feel free to poke around.

Best.
Brook Reams.
 
You may find this set of write-ups I wrote when I rebuilt a 1973 R75/5 helpful.

Yes, indeed I find (or should I say found?) it extremely helpful. While I read up on the stud removal subject, I came across your site. Loved the detailed documentation. Very well done sir!
 
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