just old or really fast?

[26667]

I'd owned an '82 R100, sold it a few years ago, and regretted it. So last fall I bought a '78 RS. But the first thing I noticed was that tho' it feels heavier ( both to lift and at low speeds) than my '82 which had a full Pichler, it also feels a LOT faster. First trip home from the purchase headed N on the 294, suddenly I was above 90 on the speedo; so ...maybe really 85, but still way quicker than the '82 got there. A few weeks later I did a carb synch and valve adj. ... the ex. valves were virtually closed! Still this bike "feels" so much stronger than the later model. What's up? What changed? Or is it all part of the aging process of motorcyclists?

[jdmetzger]

I'd owned an '82 R100, sold it a few years ago, and regretted it. So last fall I bought a '78 RS. But the first thing I noticed was that tho' it feels heavier ( both to lift and at low speeds) than my '82 which had a full Pichler, it also feels a LOT faster. First trip home from the purchase headed N on the 294, suddenly I was above 90 on the speedo; so ...maybe really 85, but still way quicker than the '82 got there. A few weeks later I did a carb synch and valve adj. ... the ex. valves were virtually closed! Still this bike "feels" so much stronger than the later model. What's up? What changed? Or is it all part of the aging process of motorcyclists?

I don't have horsepower/torque figures in front of me, but I know the 70's bikes had higher compression than the 80's bikes, and I think the 78RS had 9.5:1 compression; much higher than the 8.2:1 on the 80's bikes. May make a noticeable power difference.

[26667]

I hadn't realized the compression ratio could make such a difference. Is the gear ratio different as well? Or is compr' the big difference? And is the factory RS fairing and mount that much heavier than my pichler plastic?

[Ridealot]

I would keep an eye on the exhaust valves. If they tighten up again it might be time for new unleaded valve seats. The valves of the 70's bikes where designed for leaded gas.

[20774]

A lot of things might influence the power of the '78. As mentioned, compression ratio, horsepower, as well as the timing was changed as of January 1978 to begin to come into line with the US emission standards. Certainly the rear end gear ratio would have an influence on acceleration and top end speed. By any chance, is the '78 dual plugged? That was popular for a time...still is I guess. The '78 would have been a points system although a PO could have put on an electronic ignition system. The '82 would have electronic ignition. That doesn't help performance so much but might make for a smoother running bike. The '82 would also have had the pulse-air injection system.

As for the valves, yes all of the '70s bikes will tend to suffer valve problems, but not nearly to the same extent as the '81-'84 models. BMW finally got the metallurgy correct in '85. The '70s will eventually show valve seat recession, more so for the 1000cc models due to the extra heat from the bigger engine. Also depends on how the bike has been treated. Suggest setting the valves to a loose 0.15/0.20mm intake/exhaust and keeping an eye on them. The exhaust valve will likely be the problem child due to the extra heat.

The RS fairing was quite a step forward for a motorcycle and was tested in a wind tunnel. I don't know much about the Pichler but the RS fairing would have been quite efficient and provided for good force distribution in keep the bike planted on the road. Maybe some of the "power" you're feeling is just the effects of the RS fairing coming through the handlebars. You're "one with the bike", grasshopper!!

Kurt in S.A.

[rinty]

Gene:

The RS fairing was developed by BMW in two wind tunnels, at the Technical University of Stuttgart, and at Pininfarina, and it is very efficient.

The early and late boxers run within a few tenths of a second of each other in the quarter mile, probably because the early boxers have much heavier flywheels.

You can get the whole story from Bill Stermer's book "R 100 RS", which I highly recommend.

Your new bike probably has a stronger engine than your '82. They can vary from bike to bike.

Rinty

[Friedle]

The older you get, the faster you were. :wow

Friedle

[srb]

In addition to what has been mentioned earlier in this thread I wonder about the carbs. Did all RS models have the 40mm bings? I know that the /7 had 32s as did the 100GS when it came out. If the fairing on the '82 had been changed, any number of things could have been (final drive).

[kbasa]

My 83 RS had 40s and I believe my 84 CS has them as well. The RS had 40mm exhausts, too.

[28796]

My 83 RS had 40s and I believe my 84 CS has them as well. The RS had 40mm exhausts, too.

I believe only the big valve R100RS/R100S from early 77 & a few Euro specials got the 40mm exhaust. The ETK shows 38mm for a 78 RS. The 82 R100 would most likely have had 32mm carbs as a base model but probably got a lower rear drive then the 78 RS. I would expect the RS with higher comp & bigger carbs to be faster but not by a whole lot.

[Isamemon]

i used to race, 4 cylinder hondas, and big kow's
I know im OLD, cause my r80 is as fast as I want to go now, and my kids, all over 20 years old, tell me dad, go faster
but the r80 is good :drink wrench lubricant might have something to do with it, and the fact that now I know bones dont heal that easy now.......
well 800 cc, kind of, is fast, I want a r100 now
my oldest rides a rice 599 that will blow this old r80 away.....
beside, you can kill your self at 5 mph with a bump in the "wrong" place just like you can drown in two inch of water

[26667]

yes, the Stermer book is great. Mine has 40 mm carbs as did the '82. looked up the vin and mfr month was Jan. of '78. No it's not like running a...i don't know what...modern bike, but noticeably quicker and faster than the '82. Judjing by what's been suggested here I gotta go w comp ratio, and drive ratio. Tho' the 82also went thru valve jobs like "Sherman thru GA," i.e. three top ends in 85 k. Two the result of the oem valve problems often discussed, and a dealer not getting the bulletin from BMW till long after the work was completed. Anyway, maybe just somehow a sub-standard mill...a 'lemon?'
Haven't had a chance to ride fast or far since the recent valve adjust on the '78, but I'm thinking of checking again at maybe 500 mi just to see if there's any change. And for the practice. PO had claimed(underlined) to have done a minor before I purchased, and i ran about a thousand mi before doing the adjust. So maybe they closed up, maybe he didn't do it. The bike had sat for 20 years.
I particularly appreciate all the responses since I'm just learning some of the basic maint' techs and having a ball.
Best,
g

[vanzen]

If the '82 is an RS, it would still have the big valves and 40mm Bings, wouldn't it?

If both are 1000cc motorbikes, FD ratio would be the same. Differences in CR would mean little to real or perceived performance – but a bunch to being able to run pump gas. Cam timing, also a concession to the above, but again, not really noticeable.
BMW was struggling to meet the demands EPA regs and the loss of leaded premium fuel and still maintain the performance levels achieved with the R90S. Both the '78 & '82 were rated at @ the same HP with similar performance.
Between the '78 and '82, the change that would most affect "perceived" speed / acceleration would be the lighter flywheel of the '82 – less weight there will make a Type 247 rev quicker and feel snappier.

[28796]

If the '82 is an RS, it would still have the big valves and 40mm Bings, wouldn't it?

If both are 1000cc motorbikes, FD ratio would be the same. Differences in CR would mean little to real or perceived performance – but a bunch to being able to run pump gas. Cam timing, also a concession to the above, but again, not really noticeable.
BMW was struggling to meet the demands EPA regs and the loss of leaded premium fuel and still maintain the performance levels achieved with the R90S. Both the '78 & '82 were rated at @ the same HP with similar performance.
Between the '78 and '82, the change that would most affect "perceived" speed / acceleration would be the lighter flywheel of the '82 – less weight there will make a Type 247 rev quicker and feel snappier.


The fact that they were both 1000cc doesn't mean the FD ratio would be the same. Depends on which model it was & we haven't really found that out. When you are talking about the difference between 8.2/8.5 & 9.5 comp ratio there is a noticible difference in performance.

[terham]

The older you get, the faster you were. :wow

Friedle

So true. As I get older, I was also better looking. :laugh

[26667]

plus, didn't I used to be smarter than my dad?

[Isamemon]

you know
today, I feel older, 2007
I dont know if it because the years are creepin up on me, or my bike is fast
so with the title of the thread, old or really fast
Im not sure
Im sure some 18 year old says I ride a slow scooter
but this old scooter will make me pucker, and if I drop it, these old bones dont heal as fast as when I was a kid
but the object of life is " not drop your scooter"
and you can kill yourself on a vespa, an "antique" honda 90 or a new duc 1098 ( 160 horses, what do you do with that on the street ?)
Im actually glad I made it to 2007 with all my stupid actions especially on a scooter, Ive dropped too many times, not always my fault....sure......
so I guess, old or really fast, is a matter of how you look at life and how fast you heal :bikes

[vanzen]

FD ratios: guess I assumed 2 RSs which likely would have the same ratios – but yes, a different ratio would provide substantiallly different performance characteristics and "feel".

8.2 vs 9.5: all else being equal, I'd bet you couldn't tell which was which.
Well, sure, I'm exaggerating the point, but, I have have owned post '81 light flywheel motorbikes with 8.2, 9.5, and 10.5 CR and the difference is not so great – compared to the differrence in "feel" between a light flywheel '82 and a heavy flywheel '78 machine (owned some of those too)

I still maintain flywheel weight would be THE major contributor to perceived performance differences, '78 vs '82.

[Isamemon]

I have ridden tons of bikes,,,,,,,,,,and dont shoot,....the shifting of a 70's era BMW is like riding a Harley as far as transmissions go............first gerar...CLUNK...second.......clunk........after that they seem to smooth out......this is why, when I HAVE to go into the tranny or the clutch, on an old airhead...a light flywheel is just assumed as part of the deal
dont take me wrong, Id take my airhead now, over a hog , over any scooter, no prbolem,
Im looking forward to this ol girl with a light flywheel, cant wait to see if its as smooth as a 70's era honda.( comparing 70's to 70's).......sorry

[flash412]

Back in "the day" of the Airhead, the MOA ON had a regular column by "Dr.Curve." He was a resident hop-up guru. His opinion was that the '78 R100RS was the strongest (airhead) motor BMW made. Having owned more than two dozen airheads (nearly every /2, /5, /6 model, plus many others), including a '78 R100RS, I have to agree.

Check your valve clearances every 1000 miles and keep a log. If you see them moving at 1000 miles, get new valve seats BEFORE you drop a valve. If you can SEE the valves tuliping when you look in the spark plug hole with a flashlight and slowly turn the motor to where you can see the valve, STOP RUNNING IT NOW and get new seats. New valves and seats are a whole lot cheaper than a complete new jug on one side and new valves and seats on the other.

BTW, Airhead transmissions shift as smoothly as butter, up and down, with or without the clutch, if you have the ability to match engine and road speeds, even with the stock flywheel. (Sometimes it really is about rider-error.)

[26667]

Thanx, Flash. i plan to peek at the valve clearance asap, but hard to put on any miles for a couple months yet. I realized later that of course the po didn't adjust the valves before i picked it up. The gaskets were a small bitch to get off. If he had those head covers off, I'll go GET a hat and eat it. So it sat since 1984, I rode a thou' and then adjusted to 4 & 8.
I haven't relly "winterized" yet so I'll take a peek inside when I pull the plugs.
I've read that a "squirt of oil in the spark plug hole is a good idea for the winter. 20w50? what squirts good? A turkey baster or the like? How much really?
Thanx, guys.

[lkchris]

Gear ratios are same between your former '82 and the '78 RS.

Yes, the '78 has a bit more power, but I'd offer the difference is the fairing.

Your "sense of speed" is significantly determined by feel and hearing, and wind blast and wind noise are reduced enough by the RS fairing to get you going faster to the point where these senses feel the same as they did on the unfaired bike.

When you then look at the speedo, you're going faster.

I've always said, the whole world's downhill on an RS.

[tuber1]

I believe only the big valve R100RS/R100S from early 77 & a few Euro specials got the 40mm exhaust. The ETK shows 38mm for a 78 RS. The 82 R100 would most likely have had 32mm carbs as a base model but probably got a lower rear drive then the 78 RS. I would expect the RS with higher comp & bigger carbs to be faster but not by a whole lot.

right, only a few RS models were big pipers...you prob couldn't even find one now

[Braddog]

right, only a few RS models were big pipers...you prob couldn't even find one now

I only have to look as far as my garage. I ride it every day in the warmer months.
:german

[kbasa]

BTW, Airhead transmissions shift as smoothly as butter, up and down, with or without the clutch, if you have the ability to match engine and road speeds, even with the stock flywheel. (Sometimes it really is about rider-error.)

Totally agree. Airheads don't suffer hamfisted operation well, in any way. They're a machine that's all about finesse and smoothness.

[BubbaZanetti]

Totally agree. Airheads don't suffer hamfisted operation well, in any way. They're a machine that's all about finesse and smoothness.

so glad it's the bike i learned to ride on, i never felt the transmission was "clunky" cause it was all i ever knew. the oilhead transmission is a bit better, but nothing compared to a modern Japanese liter bike........i don't find the clunk to be annoying at all, although that preload thing took a little getting used to when i was brand new to riding.