1971 R75/5 Tranny Output Flange

[james.a]

A couple of things.
1) The kick starter is darned handy to have when you are turning the motor over to adjust valves and/or set the timing or points.
2) The 5 speed transmission is a small improvement over the 4 speed in that 4th gear on the 5speed is the perfect kick down passing gear when you are motoring along close to the speed limit. When you drop a gear to pass with a 4 speed, the R's go up to where you are on the waning end of the power band.

 

[fxray]

FWIW, here's the bottom of my '74 R90/6 gearbox, with the two-wire switch. It is a 5-speed and has '74 cast into the case. It is the original box.



DonTom, since you said your gearbox had been apart once before at a dealer, and hearing what steps you have been through (giving it hammer shocks while under tension with the puller), it sounds like they might have done you the "favor" of using a bit of Red Loctite on the taper the last go-around? I hope not, and good luck with your repair.

Ray

 

[DonTom]

While I loved the kick starter function on my /2 and my /6, I agree with above that it would be a waste to spend the extra bucks to get what you essentially don't need. There is always "bump" starting which is very easy in 2nd gear, and if you watch where you park, you can part upside of an incline and just "coast" it to start it!

The time I was stuck near Phoenix, I was on a level freeway. But I had a friend with me, so that should have worked, with a push.. I never tried a push start on the BMW on level ground--no need to try anything other than the kick starter, But my other three bikes don't have a kick starter--but they all have a better charging system too than 180 watts near redline (or whatever it is on my 1971 R75/5).

On my "headlight-always-on" /7, I wired in a switch (using "USA" circuit which was still there) so that I can turn off lights when I need to.

I did that too on all my bikes other than my 2013 Triumph Trophy SE. Still too new to modify--still in warranty.

-Don- Reno, NV

 

[DonTom]

All these show just one wire to the switch...the ground is made by the switch internal to the transmission:

http://rna.ucsc.edu/albion/bmw/images/slash5_wire.jpg
http://www.powerboxer.de/images/stories/schalt_wart/schaltplaene/im_01_strich5_schaltplan_e.gif (switch is #13)

When you get to the two-wire setups, they would be like this for the late /6s:

http://www.powerboxer.de/images/sto...ltplaene/im_03_strich6_75-76_schaltplan_e.gif (switch is #20)

I am not seeing the big difference . .

Aren't they both normally open switches that ground the low side of the neutral indicator as long as the extra /6 switch connection is grounded?

-Don- Reno, NV

 

[DonTom]

A couple of things.
1) The kick starter is darned handy to have when you are turning the motor over to adjust valves and/or set the timing or points.
2) The 5 speed transmission is a small improvement over the 4 speed in that 4th gear on the 5speed is the perfect kick down passing gear when you are motoring along close to the speed limit. When you drop a gear to pass with a 4 speed, the R's go up to where you are on the waning end of the power band.

Well, that clearly shows the advantage and disadvantage of the five speed vs. four speed. Which makes it a tougher decision to decide which is best for my /5.

But my /5 is pointless--I put in the Dyna Ignition System many years ago. Four spark plugs-- but mine still with six volt coils and a waste spark. I also have Mukuni carbs since the /5 Bings only belong in a trash cans, IMO. I don't care about keeping things stock or resale value or any of that stuff. I never sell motor vehicles--I just use them until they are junk that nobody would want.

But it seems parts and tools are easy to get for the BMWs so they last forever.

-Don- Reno, NV

 

[20774]

Yes, they might be normally open switches, but they work differently in the way that they close. Tom Cutter referred to the earlier 5-speed switches as "innies"(#23 14 1 352 153) gets pushed in to make the connection. The later 5-speed switches (#61 31 1 243 097) were "outies" and get pushed out to make the connections. The pushing has to do with the cam that the switch rides on inside the transmission. When you select neutral, a cam rotates into position that either pushes out or lets the switch extend in to make contact.

In this picture for the /5, #13 has only one wire going to it...note the electrical ground symbol shown with it. So that means that when the switch is moved to the right position, internally the contacts are made and the switch itself then acts as a conductor to ground.

http://www.powerboxer.de/images/stories/schalt_wart/schaltplaene/im_01_strich5_schaltplan_e.gif

In this picture for the later switch, #20 has two wires going to it but no ground symbol is showing for the switch. So that means that when the switch contacts are closed internally, the circuit is completed from one of the wires to the other wire. The wire colors are BR and BR-SW. BR is brown and flows through #19 to ground. BR-SW means "brown switched" goes elsewhere in the system to complete its circuits.

http://www.powerboxer.de/images/sto...ltplaene/im_03_strich6_75-76_schaltplan_e.gif

 

[DonTom]

Yes, they might be normally open switches, but they work differently in the way that they close.

But does it make any difference? It's all internal in the tranny, right? I mean, are they interchangeable or does it mean some bikes won't have a working neutral indicator after the tranny swap?

-Don- SSF, CA

 

[20774]

But does it make any difference? It's all internal in the tranny, right? I mean, are they interchangeable or does it mean some bikes won't have a working neutral indicator after the tranny swap?

-Don- SSF, CA

Don -

The real point here is that you have to get the right switch that is compatible with the transmission. The switch is just that...a switch. But the internal cam plate is what causes the switching. As far as I know, the switches look identical. And for people with transition year bikes, say '75 to '76, hopefully just providing the VIN will be enough to get the right part, but sometimes not. For sure, check for proper operation of the switch before installation in the bike and/or filling with oil.

 

[DonTom]

Don -

The real point here is that you have to get the right switch that is compatible with the transmission. The switch is just that...a switch. But the internal cam plate is what causes the switching. As far as I know, the switches look identical. And for people with transition year bikes, say '75 to '76, hopefully just providing the VIN will be enough to get the right part, but sometimes not. For sure, check for proper operation of the switch before installation in the bike and/or filling with oil.

IOW, I guess you mean I have to make sure the switch matches the tranny. But don't the trannys, if bought used, usually already have the correct neutral switch built in?

BTW, I just called the BMW shop to ask about my tranny. They said they will take a look at it again in the morning. Perhaps by tomorrow afternoon I will hear something. But I am trying to decide if it's worth while to look for a later 5 speed tranny, say from a 1977 to 1980 airhead, if the only possible issue is the neutral switch.

-Don- SSF, CA

 

[20774]

IOW, I guess you mean I have to make sure the switch matches the tranny. But don't the trannys, if bought used, usually already have the correct neutral switch built in?

Sounds right. I think the issue would be if you decided to replace the switch. Then you need to make sure you get the right one.

 

[DonTom]

Sounds right. I think the issue would be if you decided to replace the switch. Then you need to make sure you get the right one.

OKay, if I understand all this, I can install a tranny from a 1970-1980 BMW, from an "R" anything, but I should avoid 1974 as is has the redesign bugs. So the next question is should I be looking for a five speed and forget about the kick starter? Is it a worthwhile change, IYO? Sounds like it is, if I can find one at a good price on e-bay or wherever.

I figure if I am going to upgrade the tranny, now is the time to do such, since my old one is removed.

-Don- SSF, CA

 

[DonTom]

Does this guy have his year wrong or what?

What is it really from?

-Don- SSF, CA

 

[20774]

OKay, if I understand all this, I can install a tranny from a 1970-1980 BMW, from an "R" anything, but I should avoid 1974 as is has the redesign bugs. So the next question is should I be looking for a five speed and forget about the kick starter? Is it a worthwhile change, IYO? Sounds like it is, if I can find one at a good price on e-bay or wherever.

I figure if I am going to upgrade the tranny, now is the time to do such, since my old one is removed.

-Don- SSF, CA

Don -

I think that just about any decision you make will work. I've never had the "luxury" of having a kick start on my /7, so it's not something I miss. The situations where I've needed something like that (which have been rare), I've been able to bump start the bike. But if it's part of your "DNA" with owning an Airhead, then maybe you should consider that a priority. I wouldn't take a non-kicker box and convert it, though...way, way expensive for the payoff. If a kick start box is available and seems better from a service standpoint, get it...and vice versa. If it's a toss up between two choices, it would seem having the kick starter would sway your decision. Nothing wrong with that. So, I think whatever presents itself as a decent option, take it.

 

[20774]

Does this guy have his year wrong or what?

What is it really from?

-Don- SSF, CA

According to Snowbum's site, the serial number ZSA097296 does appear to be a 1984 model...a little confusing with his notations for using Z and ZSA. It may or may not have the shift kit installed. I can't tell from the ad if maybe the box was bought and modified for an earlier model?? I can't tell but from my eyes, the input splines appear to be the longish type which I thought meant it was for a pre 1981 clutch/flywheel. R65s were odd ducks in various ways, so I don't know if a transmission meant for that model is universally OK for other models. Hard to say what is going on.

 

[DonTom]

Don - If a kick start box is available and seems better from a service standpoint, get it...and vice versa. If it's a toss up between two choices, it would seem having the kick starter would sway your decision. Nothing wrong with that. So, I think whatever presents itself as a decent option, take it.

I recall there were some kick starters on some five speed BMW trannys--but I cannot remember the year. But I think they have been added. The SF police department was using airhead BMW's with kick starters, but perhaps that was in the 1980's--too late for my bike.

Perhaps the shop will have my tranny fixed today. I could still look for a five speed, then I can have both and see which I like best. I assume the five speed, at least until I need the kick starter for whatever reason.

-Don- SSF, CA

 

[DonTom]

Should I be using synthetic gear oil in my 71 R75/5 tranny? I never have, but It seems to indicate I should do such here.

-Don- SSF, CA

 

[20774]

GL5 80w90 gear oil. I'm not sure there's straight mineral gear oil out there...it's mostly some portion of synthetic. I've been using Castrol HypoyC and maybe Valvoline. You want a good quality hypoid gear oil.

 

[DonTom]

GL5 80w90 gear oil.

That has been what I have been using. I didn't just realize it was synthetic (or partly such).

-Don- SSF, CA

 

[PGlaves]

GL5 is an API rating as a gear oil suitable for hypoid gears (spiral bevel gears running at an angular contact below or above the centerline of the pinion gear. 80W90 is a viscosity index for the gear oil. Both GL5 and 80W90 specifications are available in both synthetic and non-synthetic gear lubricants. A 75W90 specification is more common for synthetic stuff but 80W90 is available.

 

[DonTom]

I just took a drive to San Francisco and offered $360.00 cash for this and they accepted. So now I can start putting my bike back together and soon have a spare tranny--maybe!

It looks like they forgot to take it off e-bay.

I spent the last hour cleaning it up. It doesn't now look so filthy.

But this one doesn't have the rod (that goes through the tranny)for the clutch. So I have to pick up my rod from the other shop tomorrow.

BTW, is there room to install the clutch rod if I mount the tranny first on my 71 R75/5?

But I will probably wait until I have the rod anyway.

The shop said they will start work on my tranny right away (I heard that before). They say that they just got the bolts in that my flange stripped on their tool as happened on mine. Now, they are going to try stronger bolts. I gave them permission to do whatever is necessary to get the thing out. I realize something might get destroyed in the process, beside their tool.

I thought with their experience, they would have less trouble than I did. But I guess not. I never removed a flange before, and I thought the problem was that I didn't know what I was doing.

BTW, have any others here had that problem of not being able to remove the flange--and destroying the tool bolts instead? Perhaps the treads on the flange will get destroyed in the next attempt, but what else can be done?

-Don- SSF, CA