Author Topic: BMW R100 Airhead (Read 35477 times)

Scott S · « **Reply #25 on:** November 05, 2015, 10:02:16 AM »

I have a manual and I'm trying to follow the directions. I've also been reading Snowbum's site, but he can get a little....verbose...and that doesn't help a person that thinks the electrical system is black magic. :permazot

Here's what's behind my cover:

I did the Regulator check by removing the B+ wire from the dode board (red wire on the right in the pic) and checking between it and the D- on the alternator.
I got a very low reading.... like 0.22 volts.

I also did a regulator check. The regulator appears to be new-ish. I unplugged it and placed a jumper between the blue and blue/black wires. This made the light on the dash go out. That tells me the regulator is faulty.

I'm trying to check the alternator, but I get to step 7 in my manual and get confused.
I don't see a D+ on my alternator and I can't determine what lead on the diode board that is.

The manual says it's #6, a blue wire(s). I don't see a blue wire on mine and the spacing isn't exactly the same as this diagram.

First of all, do I even need to go any further or have I determined that it's the regulator? What do those crazy low readings on the alternator mean? That I've done the test wrong or ??
If I need to do steps 7 and 8, can someone guide me through that using the pics I posted.

Lastly, the brush holder has a crack in it, but the brushes seem plenty long and are making good contact.

What next? I'm an absolute noob to the BMW and electrics confuse the heck out of me. Talk to me like I'm a dummy....I won't get offended.

Scott S · « **Reply #26 on:** November 05, 2015, 01:36:34 PM »

OK, my good friend and Electrical Engineer Pamco Pete came over and helped me trouble shoot. I can't begin to tell you what all we did (and by WE I mean HE...), but here's the synopsis:

The VR, rotor, diode board and alternator all test good. It appears that there's a bushing or insulator missing on the alternator, which means that the POS + brush is grounded. We used a piece of cardboard between the spring and brush to test it and the charging light goes out, voltage rises to 13.5+ when revved and everything seems to work properly.
The missing spacer/insulator might also explain why the brush holder is cracked.
Oh....and someone had the wires crossed on the brushes....probably in an attempt to troubleshoot or repair this same problem. That means that all the testing in the world "by the book" would have led me nowhere. It simply wasn't assemble properly.

Here's a pic from the web showing the spacer:

Scott S · « **Reply #27 on:** November 05, 2015, 01:37:12 PM »

It looks like all I need is a new brush holder, the proper spacers and new brushes.

Is this everything?
http://www.euromotoelectrics.com/Bosch-Alternator-Brush-Kit-BMW-R-Airhead-p/boalt-brushholder.htm

Scott S · « **Reply #28 on:** November 05, 2015, 02:49:22 PM »

Here's a pic of mine for comparison. If you look closely, you can see that it's missing the washer/spacer/insulator. You can also see the crack in the brush holder and the strip of cardboard we used to get the brushes to work properly.

Scott S · « **Reply #29 on:** November 05, 2015, 03:24:10 PM »

I also have a few more questions....

I looked at the throttle cable while I had the tank off. There's a ton of slop in the cable. I backed out where the cable goes from 1-2 but it didn't really do much. Do I just need new cables?

Video:

Also, I noticed that the dual plug heads/coils have one lead from each coil going to each cylinder. Wouldn't that mean that the coil is firing on that cylinders exhaust stroke? Is that the whole point of dual plugs? Or should the coil fire both plugs at the same time?

I also tried to check the timing and it seems way off. The "S" mark isn't even in the window, no matter which of the 4 wires I use. I didn't try to adjust it yet because I wanted to understand the dual plug stuff. The bike starts instantly and idles great. It pulls OK to 3-4K and then hits a flat spot. I can't tackle the carbs until I get the timing and throttle cable sorted.

Scott S · « **Reply #30 on:** November 05, 2015, 04:41:36 PM »

Here are some pics of the throttle. This pic is with flash and shows the teeth/gears.

Same pic without flash.....is that ramp supposed to be there or is that wear?

This is the other end of the slot or groove that's closest to the rubber grip. I *think* I can see a dash or mark on the 2nd tooth.

These are the gears underneath.

Do I align the dot near the chain or use the dash mark ~90 degrees out? If I align the dash, there's a mile of slop. If I align the dot, it wants to skip a tooth when I turn it (admittedly, without the cover installed....only holding it down with my hand), which might indicate wear?

Should I align the dot on the gear with the mark on the 2nd tooth on the throttle, install cover, and see how it goes?

Scott S · « **Reply #31 on:** November 14, 2015, 08:29:08 AM »

I got the new cam, cover and throttle grip installed. Right away, about 75% of the slop was gone. I took up some more slack under the tank where the single cable splits to two. That made it even better....about what I'm used to up at the grip.
But I'm still not getting full throttle. I noticed that the lock nut and adjuster down at the carb(s) was screwed all the way down/in. I backed them out an equal amount (eventually, I'll get it running again and sync them with the manometer) and that helped even more. I'm still not getting quite 100% full throttle. I guess I just need to keep backing them out until I can achieve full throttle? And...now that they're backed out like that...sometimes the throttle doesn't return. Will it be better once the engine is running and I get some vacuum on the diaphragms? Could it be that the return springs are worn? Or should I have bought cables, too?

I have a Haynes manual and it's a bit inadequate when it comes to adjusting the throttle....especially lacking in pictures. Is there a good "How-To" you can point me to? I mean, I get the basic idea....but I'd like to see it done one time.

These screws were bottomed all the way out. Why, I don't know. Guess just keep adjusting until I can get full throttle?

Do the springs lose tension over time? Or is something else causing the throttle to not snap back?

Scott S · « **Reply #32 on:** November 14, 2015, 10:38:50 AM »

GRRRRR!!!!
I took the oil filter cover off so I could remove the paper gasket and now the hole that's behind the header doesn't feel right to me! It's not stripped.....yet...
Looks like I'll be removing the exhaust AGAIN so that I can go in nice and square. I'll chase the threads and make sure everything fits smoothly. Stupid 5 minute job....

Roach Carver · « **Reply #33 on:** November 14, 2015, 12:27:58 PM »

Back that throttle screw all the way out for now. These are cv carbs if the throttle doesn't snap back pretty easily then there is something going on with the cable. Also make sure you have the throttle tube and gear oriented for the full movement

Scott S · « **Reply #34 on:** November 15, 2015, 10:11:52 AM »

Made a thread chaser by cutting three grooves in a bolt and it worked great! Was able to get the cover back on without removing the exhaust.

I also got the throttle working properly. I cleaned up the bar and re-lubed everything and went through the whole adjusting process again. I think the biggest culprit was the rubber sleeve for the bar end mirror. It's damaged and, even though it didn't touch the grip when initially installed, it mushrooms out of the end of the bar when tightened up. That was making it rub on the end of the grip/throttle sleeve just enough to be a problem.
I now have full throttle and the carbs snap back as they should. I still need to sync and adjust them....soon....soon....much closer than I was before. And, worst case scenario, I just need a new mirror.
Anyone have a busted up Napoleon Bar End that I can rob the insert from?

Scott S · « **Reply #35 on:** November 25, 2015, 05:25:47 AM »

I had a buddy come over yesterday and we found true TDC on both pistons. My GF was helping me the other day and she said that she thought the new mark was off by 7 or 8 teeth. That didn't make sense and turns out it's off by much more, which makes sense. It appears that the flywheel is off by one bolt and they marked new TDC.
Next time I'm in there for service, I'll install it correctly.

With true TDC on both pistons, I rechecked the valves and tightened up on the intakes since they were a little loose. The bike sounded better right away. It idles nice and will rev freely in neutral, but it's still breaking up in the mid range, around 2500-3500 rpm. I synced the carbs with a manometer and that helped, but the symptoms are still there. Guess I'll be pulling the carbs. I might try taking a look at the diaphragms and dropping the bowls to pull the jets and see if I get lucky first.

RE: Timing
At idle, the mark is below the window a little bit. I have to stand to the rear of the bike and shine the timing light down to see it. At 2000-2500 rpm, it's dead centered in the window. If I keep revving, it continues to rise and leaves the window entirely.

Roach Carver · « **Reply #36 on:** November 25, 2015, 06:47:41 AM »

a lot of the time i do a down and dirty clean up on my carbs without removing them from the bike. I take off the tops and the bowls and do a little carb cleaner and air in the holes I can reach easily. That's my spring start up

and it is usually adequate. as far as the timing i cant help you there. It is not that hard to get in there to fix the flywheel. Maybe a day to do the job start to finish but if you have to go in there I would go ahead and replace the rear main seal. make sure to block the crank. if you are not familliar with that procedure look it up before you dig into it. It can be a major problem if you forget to do it.

Scott S · « **Reply #37 on:** November 25, 2015, 01:34:13 PM »

I'll do that, probably next week when I get a few consecutive days off.
If I end up keeping this bike long term, I'll eventually get the flywheel on correctly, too.

Scott S · « **Reply #38 on:** December 01, 2015, 12:21:56 PM »

I pulled the top and the bowl on the RH carb to take a look. Uh.....yeah....probably at least part of the problem....

The carbs are pretty filthy. I started trying to clean it with carb cleaner and compressed air, but I think it's time for a REAL cleaning. Luckily, the diaphragms look fine. While I was messing with the carb, I noticed that the RH petcock wasn't holding. The LH has a repair on it and I knew it leaked. I got pissed and watching the petcock pissing, so I pulled the petcocks and drained the tank.
Yup.....not gonna be able to rebuild these. Time to order two new petcocks.

The tank wasn't too bad. Some of the factory liner has flaked off, but it's solid and rust free. I drained it, flushed with water to get all the flakes and sediment out, then flushed with demineralised water, followed by swishing some denatured alcohol around. I blew it out with air and my heat gun. I'm letting it air out now and, if it doesn't stink too bad, will bring it in tonight and set it over a heat register.

While I'm at it, I plan on ordering new fuel line, too

Back to the carbs: I have a bucket if Berryman's, spray carb cleaner and compressed air. I have the RH carb mostly apart. I haven't removed the choke body yet. Is it safe to dunk the carb in the Berryman's with the plastic cover on the opposite side of the choke? Other than the O-rings on the jets, are there parts that should NOT be dunked?

Lastly, both needles have the tiniest ridge on them. I cleaned them with 0000 steel wool and carb cleaner, but there's this teeny-tiny little lip that I can barely catch a fingernail on. Is that a problem?

Roach Carver · « **Reply #39 on:** December 01, 2015, 12:36:59 PM »

I would be leary to dunk any of it that i did not take all the way apart but that's just me. I would disassemble as far as I felt comfortable with and clean with carb cleaner and fine wire. Probably would not be a bad idea to replace the needle while you have them apart and I would recommend replacing the diaphragms as well. They get stiff and don't work as well as they should. Also get genuine BMW braided hose or VW hose will work as well (or so I have been told) If you decide to take the butterflys off the shaft you need to know that the screws are peened in place so they will likely need to be replaced and possibly the throttle shaft as well? I suspect if you get all that trash out of the system and get clean fuel in there even with worn parts it will probably run quite well. The carbs are pretty simple but are still susceptible to trash in the lines.

Roach Carver · « **Reply #40 on:** December 01, 2015, 01:42:29 PM »

what size Delortos, and pump or no pump. sorry for the small thread jack.

Scott S · « **Reply #41 on:** December 01, 2015, 01:55:02 PM »

Cal, what kind of deal are we talking?

I just spent 30 minutes on the phone with Tom Cutter. He advised me on the timing as well as the carb issues. New parts are on the way: carb kits, petcocks, fuel line and needles/jets. I will do a bath of Simple Green and hot water and reassemble the carbs with new needles. He also seems to think the timing is too retarded for the DP heads.
Hopefully, after I'm done with all this, the old girl will scream!

dusterdude · « **Reply #42 on:** December 01, 2015, 03:03:45 PM »

Yea,we know you

Scott S · « **Reply #43 on:** December 22, 2015, 04:39:39 AM »

Been a while since I updated. I've been working like crazy and, in all honesty, taking a break from this thing from time to time. I've also been trying to read up and learn about all it's quirks, especially since someone not so "knowledgeable" seems to have been working on it before I got it.

While addressing the valve cover leak, I found a failed Heli-Coil on the LH head. Seems that is a common failure when people try to over tighten the valve cover. I have a good friend that's a retired mechanic (air cooled VW specialist, too!) and he's going to Time-Sert it for me. He showed up yesterday and, of course....like everything else on this bike...someone has really hogged out the hole for the Hel-Coil. The 8 x 1.25mm Time-Sert he brought that should have been the right size is too small. He has the parts but didn't bring them with him. Another day, another delay.

Scott S · « **Reply #44 on:** December 22, 2015, 04:50:10 AM »

Since I'm feeling a mid-range "flat spot" or poor running, I thought I'd do a "quick and dirty" on the carbs by pulling the bowls to drop the mains and needle jets and pull the tops to check the diaphragms.
The carbs didn't look so clean, so off they came.

The diaphragms looked OK; no splits or tears or anything. I ordered rebuild kits anyway. There was some wear showing on the needles and I could actually snag a fingernail on the groove/wear mark on one of them (it was on both, but one seemed deeper), so I ordered new needles/needle jets, too.
The brass bits and bowls got a soak in a bucket of Berryman. The bucket I have is probably 20 years old and will STILL curl your nose hairs! I wanted to avoid removing the peened throttle screws so the carb bodies got a bath in hot water and Simple Green, followed by cleaning all passages with carb cleaner and compressed air. The needles look to have been on the 2nd position from the top...about 47mm when measured...so that's where I went back with them. All other jetting looks to be stock as well. I also set float height while the carbs were on the bench.

Wear on the needle.

Old on left, new on right.

I managed to split an O-ring for one of the mixture screws, so I'm waiting on replacement. The carbs are otherwise done and back on the bike. I also installed new fuel line, ordered two new petcocks and drained and flushed the tank. I fogged the tank with Sta-Bil marine tank fogger while it waits.
All of this ought to rule out any fuel delivery problems.

Scott S · « **Reply #45 on:** December 22, 2015, 05:07:25 AM »

I also spent a little time trying to understand and find true TDC on this bike since the flywheel is installed off by one bolt. I know the proper fix is to install the flywheel correctly, butI need to prove to myself that it will run like it should first.
THEN I'll worry about fixing the flywheel.

After a lengthy discussion on the Facebook Airhead Beemers page, I got a really simple explanation from Tom Cutter of Rubber Chicken Racing. Actually, I got lots of good information during that discussion, but his was simple, straight forward and in language I could understand.
Basically, it boiled down to this:

"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 found true TDC several times yesterday, mostly as a sanity check to make sure I was doing it right. Then, when my retired mechanic buddy came over I had him check my work. He agreed that we were at TRUE TDC. I also checked the valve clearances while there and they were spot on.
I also found this picture on the Internet. (This is NOT my flywheel and appears to be a severely lightened one at that.) This pic helped because A ), those are the types of markings on my flyhweel, and B ), it helped me see the actual 9 tooth count between markings.

After finding true TDC, I marked a tooth on the flyhweel with a yellow paint pen and the counted down nine teeth. I counted at least three times, going in both directions. It turns out that the white paint mark that I WAS seeing, the one that someone before me added, was only seven teeth from TDC.
If that's the case, and if I understand this correctly, my timing is in fact advanced too much. And with dual plug heads it should be retarded by 3 degrees or so, correct? The old, previous white paint mark is getting to the center of the timing window by 2,000 - 2,500 RPM. The REAL full advance mark is still two teeth down and should be in the window at 3,100 rpm.
This, too, could be affecting the mid-range, no?

simon#42 · « **Reply #46 on:** December 22, 2015, 10:26:26 AM »

scott , just in case you have not seen this site

http://bmwmotorcycletech.info/technical-articles-list.htm

loads of information , possibly goes into things in to much depth unless you are a sad nerd like me .

Scott S · « **Reply #47 on:** December 22, 2015, 11:35:09 AM »

Oh, I'm very familiar with that site. It gives me a headache trying to sort through it all, though. If he cleaned up those pages, it would be even more invaluable.

Roach Carver · « **Reply #48 on:** December 22, 2015, 12:27:31 PM »

snowbums site? if thats it, I agree. Its still burned into my memory. I dont go there unless i absolutely have to.

I bet when you get the timing close and those carbs in good shape you will have a totally different machine.

Scott S · « **Reply #49 on:** January 09, 2016, 05:30:08 AM »

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.

News:

Author Topic: BMW R100 Airhead (Read 35477 times)