Author Topic: BMW R100 Airhead (Read 35298 times)

Scott S · « **Reply #50 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!

calj737 · « **Reply #51 on:** December 01, 2015, 02:53:15 PM »

Well, you know me, and it is Christmas time... How about close to what I paid to have them rebuilt with all new, perfect and proper BMW NOS components? PM me if you are genuinely interested.

dusterdude · « **Reply #52 on:** December 01, 2015, 03:03:45 PM »

Yea,we know you

Scott S · « **Reply #53 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 #54 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 #55 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 #56 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 #57 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 #58 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 #59 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.

Scott S · « **Reply #60 on:** January 09, 2016, 05:32:07 AM »

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 · « **Reply #61 on:** January 09, 2016, 10:11:24 AM »

Quote from: Scott S 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.

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 · « **Reply #62 on:** February 03, 2016, 01:58:04 PM »

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.

calj737 · « **Reply #63 on:** February 03, 2016, 03:43:26 PM »

I'll bite... What you thinking on $ ?

Scott S · « **Reply #64 on:** February 03, 2016, 06:26:33 PM »

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.

calj737 · « **Reply #65 on:** February 04, 2016, 04:02:59 AM »

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

Stev-o · « **Reply #66 on:** February 04, 2016, 05:24:03 AM »

Quote from: calj737 on February 04, 2016, 04:02:59 AM

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

Ouch!

Scott S · « **Reply #67 on:** February 05, 2016, 12:35:41 PM »

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?

calj737 · « **Reply #68 on:** February 05, 2016, 12:38:35 PM »

Yes, it should stop and be stationary in the window at that held RPM. Bet you want more money now that she's running well

Scott S · « **Reply #69 on:** February 05, 2016, 01:51:30 PM »

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 · « **Reply #70 on:** February 06, 2016, 12:14:36 PM »

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 · « **Reply #71 on:** February 07, 2016, 12:54:23 PM »

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 · « **Reply #72 on:** February 18, 2016, 03:50:01 AM »

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 · « **Reply #73 on:** February 18, 2016, 04:20:54 AM »

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 · « **Reply #74 on:** February 19, 2016, 03:49:11 AM »

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.

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Author Topic: BMW R100 Airhead (Read 35298 times)