Topic: BMW R100 Airhead

[Scott S]

 Now that the head is repaired, I can get it back together and see if my carb rebuild and timing mark discoveries make a difference.

 I also took the new rear brake hose that came with the bike and went over to Cardinal Rubber. For only $16 they made me a braided stainless hose.

[simon#42]

Finally got the head stud/failed Heli-Coil repaired. It took two tries. Like so many other things on this bike, when my mechanic showed up with the 8 x 1.25 Time-Sert, we found out that the hole for the Heli-Coil was WAY bigger than it needed to be. Luckily, being a retired VW mechanic, he had a solution. When VW went from 10mm to 8mm case studs, they made what are called "case savers". It allows you to run 8mm studs in a case drilled for 10mm.
 It just so happens that was what we needed to repair the hole. He drilled and tapped the hole, then Loc-Tite'd in the case saver insert. He said it's MUCH stronger than the stock BMW set-up now.

i do this to good cases , as you say it is much stronger .  if you ever decide to make a fast bm go for the last cases that they made [ after 89 ] these are the strongest .

[Scott S]

 Trying to get reinvigorated on this project. I've had so much going on....selling other bikes, buying a new Triumph, etc.....and, to be honest, I'm just not feeling this project. I'm really hoping that the carb work and getting the timing marks correct will make a difference. The only way to fin out is to put some gas in it and fire it up. So, today I installed the new petcocks and new external filters. The plan is to add gas this weekend and check my work. Keep your fingers crossed!
 And, seriously....anyone interested in an '84 R100 project? There's not much at all left to be done and then it's down to the cosmetics.

[Scott S]

 I dunno....depends on how much more I keep fiddling with it. What's a fair price? If has all sorts of goodies; genuine S fairing, Browns side stand, Russell center stand, dual plug heads, some charging system updates, etc. Comes with two brand new tires.

[Stev-o]

Given that this is an SOHC site and its a measly twin, how about $400? 

Ouch!   

[Scott S]

Fired her back up today and the good news is that the valve cover no longer leaks, it no longer has a flat spot and it revs to redline now! Woo-Hoo!

 I do have a question about the timing....
 I verified TRUE TDC and made new marks for it and full advance. Here's the advice I was given by Tom Cutter, re: verifying TDC and setting timing with the flywheel installed wrong.

"you can also just count 9 (nine) teeth from your known TDC point. Not the random mark you found, but the actual, verified TDC point. 9 teeth will give you a Full Advance point, at about 29-30 degrees BTDC. Mark it with a different color Wite-Out or nail polish. Start the engine, raise to 3100 RPM or so, adjust the beancan so that your new Mark shows up centered at the line in the left side of the timing hole. If the engine still runs bad, something else is bad. It could still be weak spark, clogged carb passages or a valve/ compression issue."

 I can line my full advance/9th tooth mark up in the center of the timing window at approximately 2800-2900 RPM. If I go on up to the 3100-3200 he mentioned, the mark goes on up out of the window. Does that mean I'm a little advanced? Should the full advance mark STOP in the center of the window and not keep climbing once I get to the ~3100 RPM range?

[Scott S]

 Hehe... you know how that goes....

 I'll work on it tomorrow. I'll adjust the bean can and retard the timing until the mark is stationary. Then I'll sync and adjust the carbs.

[Scott S]

 I set the timing today....it was way advanced....And tweaked and tuned and synced the carbs a bit. It runs better than it bas since I've owned it!
 Sometimes it's still nit quite as crisp right off idle, from a stop, as I feel it could be, but it's much  much, much better than before. It seems to clean up and do better after  couple of minutes, even when the engine already has some heat it.
 I think some more fine tuning on the carbs and maybe even a clutch adjustment will get rid of all that. I'm thrilled with the results, though!

[Roach Carver]

Congrats! That's good news. I don't know what you are feeling but mine feels a bit like a tractor at take off. Nothing like my Honda. Glad you are getting it sorted.

[Scott S]

Things I've learned since trading my XS650 for a Dual Plugged '84 R100

* You just gotta LOVE previous owners. Coming from vintage Japanese bikes, the BMW is just different enough to slow me down. This bike was a very nice bike at one point and had lots of upgrades. Someone really cared for it and spent some money on it.
Then a few ham-fisted P.O.'s got ahold of it....
I've been "getting the previous owners out of it" for months now. When you read the manual and online advice and things still don't make sense, when you do the tests and the numbers are just crazy, it's probably because the P.O. has stuff so screwed up that all that advice just doesn't count anymore.
Luckily, all of it has been easy and cheap (or even FREE) to fix. It's the weeks of banging my head against the wall before I figure it out that takes the joy out of it. It IS very satisfying when it's fixed, though.

* It's a cold natured beast. Even after a full tune up, sync, adjustments, etc., it takes a while to warm up. Yesterday, after setting timing and syncing carbs, I cleaned up my garage and put away tools. Only ~20 minutes or so of sitting had the idle low again. Too warm for choke, too cold to idle properly.
It only took a couple hundred yards and all was well again.

* I have to settle for an indicated ~1150-1200 RPM idle. I've baselined the cables, carbs, mixture screws, etc. so many times. If I try to lower the idle, it messes up the sync. Try to adjust that and I start this endless cycle of tweaking and end up right back at...... ~1200 RPM.

* The engineering. Hmm.....what can I say? I've had air cooled VW's before (still own a '63), so I'm familiar with German engineering. But some of this stuff makes me scratch my head. It's almost like they over-engineered it just for the sake of engineering.
The throttle, for example. Why so complicated when everybody else uses the old pull cable twist grip?
And let's set the bean can up front and the timing window on the left, away from the throttle, so that it takes two people to set the timing....yeah, let's do that! (FWIW, I can set it by myself now, it just takes a little "stop and go", back and forth).

* The power. I was told that the 1,000cc is a BEAST! Especially with the dual plug heads. I wouldn't exactly say that...
The power delivery is strong and smooth, though. Very linear....it just builds speed without drama. It reminds me of my Tiger 800 Xc, in a way.
It won't pin your eyeballs in the back of your head like my ZRX 1100 will. And the CB550's let you know when you're "on the cam". You get that change in engine note and a noticeable burst of power when you get 'em up above 6,000 RPM.
The R100 just pulls. I'll be thinking "Well, this is unimpressive", only to look down and see that I'm doing 60 in 3rd gear without getting anywhere near redline. It's tractor like....in a good way....just pulls and goes without drama.

* The looks. I'm getting to like it. The S fairing. The seat cowl. Seeing those big cylinders sticking out in the wind. It's different and that's cool. Now, if I could just pick a color to paint it....
 

[Roach Carver]

It's great to cruise. It won't scream like the inline fours. It is what it is. It's nice to have options

[Terry in Australia]

Good work mate, I read all three pages and it's great to see how you've identified a problem and worked through it with a positive result.

I've owned an R69S, maintained my brother's two R75's, and owned two early R100RS'. (1979 and 1980) To be honest, the smaller air heads were smoother, sweeter engines. The bigger they got, the more they vibrated at particular RPM's, and the less enjoyable they are to ride. On top of that, the gearboxes are horrible around town, (but OK once on the highway at 60 MPH or more, they'll cruise on 100 MPH all day as long as they're well maintained) the charging systems were terrible, they don't handle as well as other European bikes of the era, and the brakes are average, at best.

BMW eventually retired their pushrod boxer engines and introduced the air/oil cooled boxers with all the mod cons in the early 1990's, and they are truly magnificent bikes. I'm in the BMW motorcycle club of Victoria here in Oz, and quite often the old air heads are compared to the new boxer engines, like old Harley Shovelheads are now compared (usually unfavourably) to Evo's, even by guys who own both.

While there is a sentimental attraction to those vibey old airheads, once you've ridden a modern BMW boxer, you'll never go back. Sell that one to Cal and use the money to buy a good used R1100S or R1100GS (I've had one for a few months now, and love it, it's everything I hoped both of my R100Rs' would be, but they weren't even close...............) and you'll be very happy. If you decide to keep it though, that's good too, you've done a lot of really good work on it. Cheers, Terry.  

[Scott S]

 I caught HELL today trying to get the rear wheel off by myself. I had to enlist the help of my Dad and remove the rear disc to get it off. I think that the old tires were at least part of the problem. Even after deflating the rear, it's so old and hard that it held it's shape!
 I finally got it off, though. Took the opportunity to lift the rear caliper and bleed it some more. I did get a little more air out. I also degreased the wheels. The rear in particular was pretty grungy. This is about the best I can do with a few can of degreaser, some Simple Green solution, and assorted brushes, SkotchBrite pads and elbow grease. It'll do for a garage build. I'll let them dry and air out for a few days, wipe them down with some acetone and use some wheel paint on them.
 I also cleaned up the rotors. I'll deglaze them and clean with brake cleaner before installation. And the rear splines will get some high pressure moly lube, too.

[Terry in Australia]

Are you gonna dump those crappy old tires too mate? I'd hate for all your good work to be wasted if your tires fall apart the first time you ride it? As I keep saying, the cheapest new tire is safer than the most expensive old tire.....

[Scott S]

 Oh, heck yeah. The bike came with two brand new Michelin Pilot Activ tires.

 I'm looking at brake pads too, while I'm in there. I like EBC and I believe I'd prefer the organics since they don't squeal and wear the rotors as fast. Is the EBC FA18 what I want? Are they the same front and rear for the triple Brembos?

[Terry in Australia]

That's a good question mate, I replaced the pads on my R100RS 3 or 4 years ago so I don't remember, but I think you're right that the pads are the same. Moto Bins in the UK are an excellent source for parts. Cheers, Terry.

[ofreen]

I may have missed it but have you done a spline lube?  If you haven't, I strongly suggest you get in there and take a look.

[Scott S]

 On the gear box? No, not yet. I will be lubing the splines on the final drive/rear wheel.
 The gear box was off sometime before I got it. I actually talked to one of the previous owners from about 4 years ago and a shop that serviced it.
 It's been in the 3 or so years in between then and me that it's been....neglected.

[ofreen]

On the gear box? No, not yet.

Yes, the splines on the transmission input shaft. The splines are dry (if seals aren't leaking), and are fine cut. They can rust and crumble away until one day you go to leave from a stop and just sit there. You have to slide the transmission back from the engine a bit, with some disassembly required to get to that point. There are plenty of instructions on the interwebs including the airhead site. Snobum's write up is thorough, as usual. Not too bad of a job, especially after you've done it a few times. I would do it before you ride it too much. Now would be a good time if you still have the rear wheel off.

[Scott S]

Now that I have the S fairing off for paint, I can get good access to the clock and voltmeter wiring and lights.
I was pleasantly surprised to find the clock works.
However, the lights for both gauges are always on, even when the key is off. I can see constant power to the clock, but the backing light, too?
If I ground either bulb to the frame, they light up. The lights shouldn't be always on, should they?

To clarify: At rest, there is no voltage to the volunteer. It works when the bike is running. Even with the key off, if I plug in the meter and insert the bulb the light comes on.
There is always voltage to the clock, even with key off. If I plug it in, it works and the light is always on, even when the bike isn't running.

I see on the diagram that they share a brown wire with the front turn signals and brown appears to be ground.. The signals are also off the bike right now (to remove fairing). Would that have an effect on the circuit?
And as I said I understand keeping voltage to the clock, but why are the lights in both gauges constantly on right now?
(Forgive me; electrical is a weak point of mine)
 

[RAFster122s]

You are going to keep going and fix all the PO's gremlins leaving none for the next guy...calj...
You know his love of arp fasteners, you really need to slow him down a few times to make him feel like he got a good deal.



So, where are you going to stop and move your deductive skills to a more satisfying target.

[Scott S]

 I have a Haynes manual and looked over the diagram in it last night.
 Looks like I'll be going over the wiring and fuse panel in the headlight bucket soon....

[Scott S]

 And the clock and voltmeter lights work as soon as they're grounded, either to the frame or to the gauge housing.

 When I turn on the key the headlight comes on, as well as the idiot light cluster (neutral, oil, etc ) but not the tach and speedo lights.
 I'm unable to crank the bike at the moment. Would the tach and speedo come on once it starts charging? Or do I need to trace those out, too?

[Roach Carver]

David - ARP fasteners are the BOMB and I'd have thrown the stock harness out and used an M-unit from MotoGadget and been done with these electrical gremlins 

I would like to hear a little about the m-unit. I bought an old Ducati and the factory wiring hurts my head. Sorry for the thread jack.

[Scott S]

No, been working all weekend. I'll get around to it soon. Luckily, it seems like I just have to trace out and move around some wires.
 I'll probably wait until I get the wheels back on it. I'd hate to knock it off the stands.