OT - Airheads Only

[Rapid Dog]

...at the risk of steppin' in a pile...I need some insight, about...airhead exhausts and advantages and disadvantages.
Evidently I've exhausted all me resources, mo pun intended.

The bike in question is my '81 R100RS
So, Roger, all, let's start if I'm not boring you...

Anyone able to identify theses mufflers? Know anything about them?
Opinions? Crap? Better worse than the OEM Zuena pipes?
Better/worse mid-range or top-end?
Let's discuss.

[roger albert]

A yes, old Luftmeister stuff. They marketed a lot of stuff than others made, kind of like Wunderlich today. Better top end, less bottom end, want fat-ish jetting, and as much idle mixture as you can stand without the motor/plugs loading up. Even then, likely some popping on decel. Pretty nice though.

[Rapid Dog]

...hmmm...interesting. I was said recently by a certain someone that "If you had a healthy motor there'd be a noticable improvement in midrange over a pair of stock mufflers"

I haven't ha a stock set of OEM Zuena's on this bike yet. These Lufty's are on it now, it does have a nice midrange, nothing mind blowing.
The issue is top end. I may be expecting more than I should. It is the 1981> low compression motor.
I did a road test this week and the best it would do was 111mph per the GPS.
I'm wondering if the mufflers are suspect.

[roger albert]

Midrange seems a tad up too, but it's not like I've done hundreds of them and am an expert. I doubt that I've even done a half dozen, and of those, about half of guys don't want to lose mileage, and don't want them jetted right. 111 is not bad for an airhead. Most of them aren't as quick as most of the owners seem to remember them, anyway, maybe 115ish. I think they must have shimmed my speedo cluster wrong and have it binding up, because when it came back from speedo-repair, it was about 11 mph slower.

[Rapid Dog]

...seem to remember them. I concur.
All I have is a couple-three airheads to comare to this '81 for reference.
Indicated top speed on my true '77RS was 134 once. Probably 125 real.

The weird thing is this '81 won't do redline in 4th or 5th. 111 is more like <65Krpm.

Bottom line I don't want to trade these off for stockers if there's no real gain in performance, not really concerned about terminal speed.

[BikerMiker]

Originally Posted by Rapid Dog

...seem to remember them. I concur.
All I have is a couple-three airheads to comare to this '81 for reference.
Indicated top speed on my true '77RS was 134 once. Probably 125 real.

The weird thing is this '81 won't do redline in 4th or 5th. 111 is more like <65Krpm.

Bottom line I don't want to trade these off for stockers if there's no real gain in performance, not really concerned about terminal speed.

Something is definitely off. Have you checked your plugs for color? If it's running rich your top end will suffer but you will still have torque.

Without bags I got up to 140 according to my crappy speedo and probably could have squeezed a few more out but I got scared (the bike needs a stiffened frame). They usually read about 10 off for some reason... thus the 11 that Roger was showing is on par. So I probably hit 130ish which never seems like a real stretch without bags. That was stock with no faring. I'm guessing you have the 40mm Carbs? I can't see the mufflers robbing you that much.

Looks in much cleaner than mine!

[Rapid Dog]

111 per the GPS 115 per the speedo.
Nope, plugs are toasty brown, all 4 of 'em.
Here's the specs:
55K
40mm Bings, all new parts.
Complete new ignition with Motorrad Elektric Alpha bean can
Dyna coils
Newly rebuilt heads (dual pugged)
Uni foam air filter
Uses nearly zero oil

Only thing that might be 'off' at the risk of opening a can o worms, is the heads are '77-'78 squishband type but still 38mm exhaust (not 77RS)

[cageyar]

By 1981, EPA restrictions had hit all motorcycle manufacturer's selling in the U.S.
Actually 1980 was the first year of less ignition advance and neutered cam durations - I recall people complaining about it at the time.
For another example, the 1980 Honda CBX had less ignition advance and much milder cams - within a few months, you could not even buy a 1979 advance unit.
The 1980 model was a dog compared to the 1979.
Don't forget, this was time of the 85 mPH speedometers as well.
Check the specs on advance degrees and cam timing/duration/lift vs. your 1977.
I wouldn't be surprised if there were significant differences and not for the better.

[Rapid Dog]

yeah, I'm probably expecting more than I should.
Bike runs well, just a little soft. I realize it's a low-comp medel.
I also had a '91 R100GS that sported a 336 cam, it would easily out run this bike in a drag race, maybe not WFO, but close.
This has all the smog stuff removed.
The ME Alpha ignition module is designed specifically for dual plugged bikes.

so, about those mufflers...

[BumbleBeemer36]

As an owner of an '82 R100...I think you're expecting too much. Mine never quite reaches redline either. Don't know GPS'ed speed but I think it hovered right at 115 the last time I let it hang out. But it felt like it could do it all day.

And my pipes are pretty much completely open.

I have serious doubts anyone's stock r100rs ever went 130-140 mph.


It's the off-the-line that makes these bikes fun. I used to love killin Harleys in Scottsdale when I was young-er and stupid-er

[BikerMiker]

Dual plugged too? ****.

Yeah what Cage said.... Valve clearances checked too I suppose?

[BikerMiker]

Originally Posted by BumbleBeemer36

As an owner of an '82 R100...I think you're expecting too much. Mine never quite reaches redline either. Don't know GPS'ed speed but I think it hovered right at 115 the last time I let it hang out.

And my pipes are pretty much completely open.

I have serious doubts anyone's stock r100rs ever went 130-140 mph.

Maybe I had a tail wind I can't say for certain that everything internal is stock or the old rusted pipes I had on it for that matter. It was most likely magic.

[tm1100s]

Found this in an old Luftmeister catalog.

Luftmeister Catalog - Muffler Page

I think the Luftmeister 2 into 1 exhausts are from this company but I'm not 100% sure.
They still have some left over, though. (from 30 years ago).

MAC Exhausts

[tjs]

what F/D is on your RS? 2.91, 3.00, or 3.09. I had an 83 R100 I made into an S. Stock F/D on that model was 3.09. I had the Luftmeister mufflers, 38 mm Dellorto pumpers, (stock R90S jetting) and K&N filters. I also added a CC products fork brace and had the swingarm braced. The combination of the S fairing and probably the Bar-end mirrors caused the bike to want head for tank slap territory at around 125 indicated. Very fast though in reaching that speed. Next shop I worked at I bought an 85 R80 and made it into a R1050RS. Sports Cam dual-plug,etc. Wish I had kept that one. tjs

[Rapid Dog]

32/11 stock rearend (2.91), valves spot on, stock jetting.

It was actually my R100/7 converted with all the 77 RS parts and an S fairing that indicated 134, tailwind, slight downgrade, barn sour for home ...

Nice find on the Luft cataloge. I've been looking for weeks for info!

[R111S]

IMO low compression is what's holding you back from reaching the top speed of the '77 Model. Unless I'm wrong the '77 had 9.5:1 Pistons right? And your newer model has 8.5:1?

Since you have Dual-Plugged Heads go for 9.5:1 Pistons and never look back.

After Dual-Plugging the Heads on my '94 R100GS/PD, I put in 9.5:1 Pistons (stock 8.5:1) and it made a big difference at all engine RPMs. It would hold redline in 5th, got better gas mileage, started better in cold temps, and low idle was very stable.

[Rapid Dog]

...actually i think its 8.2-1....low boy.
General conensus is as you say, need some hi-comp pistons.

[BumbleBeemer36]

Talkin out my butt, but didnt the low comp motors have base gasket that could be removed as well?

Sorry, halfway through an Easter morning Peach ale.

[Droptarotter]

Originally Posted by BumbleBeemer36

Talkin out my butt, but didnt the low comp motors have base gasket that could be removed as well?

Sorry, halfway through an Easter morning Peach ale.

Nope...........in the '80's they had done away with the base gaskets and used O-rings.

Oops........forgot about the late '70's motors did have different base gaskets.........but weren't the guys at that time adding gaskets so they could run cheaper fuel?
Remember...........the cheapest thing on a BMW is the rider!

Get back to your Peach ale!

Cheers

[tm1100s]

Don't remember any engines coming with base gasket that would make a difference but there was a thicker base gasket offered to reduce compression and mitigate the valve seat problem with non-leaded fuels. Tried it, didn't like it, took it out. Never had the problem, but then again, haven't put a lot of miles on it since then (/7). I'll probably install new seats this summer just because I have the equipment available to do the job.