Hi, I have just bought my first BMW an 1987 K100 RT with full fairing and bags. Wanted one for years so this is a dream come true. However, I do not know what is normal for the bike.

The engine revs up good through the first few gears, and it accelerates with no missing, but on acceleration up through the gears, the engine does not seem to go over about 6000 rpm. My Honda will redline if you don't watch it closely; the BMW does even get close.

It is not very fast off the line, about like a Honda CB750 -- of course, it is much heavier, so maybe the weight is eating up the extra 250cc. And it much slower on accelerating than a K100RS that I test drived -- the RS snapped my head back - but no fairing or bags.

Is there something wrong with it? And if so, where would I start looking? It only has 8000 miles since new. Since it is not missing at all, ignition would seem to be ok. Maybe needs plugs? or what else? I have not tried taking it over 80 on the highway, but the limit there is me rather than the bike -- it might go faster.

Also, get a LOT of smoke when starting, but not after I have gone a few miles. I have heard this is normal.

Any experiences, observations or tests you can offer?

Tom

Smoke is normal if you park the bike on the side stand.
The oil has the tendency to get in the cylinder bypassing the rings. I think that this problem was rectified in 1988. (New type of rings)

You should be able to go higher than 6000rpm. However, I believe that the K100 has a device that will limit the rpm.

Last week end, I just pushed mine to 200km/h going uphill and with a passenger. The bike was pulling like an ox.

Mine is an 1985 which has an extra 10 horsepower.

For me acceleration is a relative thing and unfortunately I can not compare to another K. My category as a rider is "older, wiser and slower" . I feel that the bike is relatively low geared and being an "under-square" engine does not seem to have the willingness to rev like a Japanese bike. I tend to shift at about 3500 revs and let the engine's torque do the work which where it really starts to shine. The throttle action, on mine at least, is quite heavy and slow and appears to be a bit of a deterrent but on the rare occasion I have accelerated past 5500 revs it appears to still have most of its 90HP left but to be fair I don't think I have seen 6000 revs and don't feel the inclination to try. As I mentioned in another post the most impressive feeling I get is rolling on the throttle in top gear from about 80k's onwards which is where beemers really seem to shine.

Regards,

Phil Mars

My K100LT from 1990 with 45.000 km can easliy rev over 6000 rpm in the three lower gears for sure. Although I only drove it once up to 200km/h, yours should be able to rev over 6000 rpm.
On the smoking, the engine has been improved during 1988. I will try and dig up the exact serial numbers (and a weblink), but since yours is from 1987 I doubt weather that will have been tackled by an overhaul because it's in the cilinder/piston.

Hi,

Some weeks ago I took advantage of the wonderful autumn weather we were having and took the bike for a ride on varied asphalt.

When I got to a new stretch of highway with brand new asphalt I was really in for a surprise. at 6000RPM bike just kept accelerating and I let go at 150KMH, as without a fairing the wind was a punishment. I think it would have gained a few more KMH if I continued at 6000RPM.

I am not likely to try going higher as one can lose one's license for a LONG time, but it sure felt bike still had a lot more to give.

I should have added that bike is a 1987 k100 base model with more then 140,000 kilometers.

This link includes the following line: -The majority of K100 do not consume oil. Until August 1988, K100 parked on the side stand were puffing a cloud of blue smoke when the engine started. The engine oil had the tendency to seep into the combustion chambers. On the 1988 models, BMW has developed pistons and rings with a different design to resolve this inconvenience. I haven't double checked it's data.

The oil seeping to the combustion chamber makes the initial smoke but only just that.

Now for not revving:
there are some things you can check: coloring of the spark plugs, check for false air (tough job), check compression of all cilinders, disconnecting sparkplugs one by one and have a look at thedrop in revs, etc.
I wouldn't check the Motronic/EFI as it seemes to be doing fine in the rang of idling to 6000 rpm. It does have a revs limiter but as faar as I know it is in the Motronic/EFI.
You get see the following fora for further (english) help:
http://www.ibmwr.org/
http://f3.webmart.de/f.cfm?id=100478
http://www.motobins.co.uk/forum.php
http://www.i-bmw.com/

Sorry couldn't find anything on serial numbers.
Can you help out on this question?

sir i also have an 85 k100 it can pullhard until the rev limiter kicks in then it will missfire and not let the rpm go over 8000and some
i love my bike it has two powerbands ; up to 4000 like for around town
then above 4000 for the highway seems to have a whole different character it screams
but lots of things can keep you from that
for me new sparkplugs and wires'adjust the valves and the big one reseal and syncronize the throttlebodies
oh yeah that little hose that connects the airbox to the #4 cyl gotta be good

i also replaced the injectors with pattern parts suggested in the tec at ibmwr that was huge when i pull out to pass a car if i wick it up i will be doing 160 k by the time i blow by
i am so tickled with my 90hp and the way bmw has engineered it
and i hear there is a 1200 what about the new1300 with 175 hp
mere mortals shouldnt have such power and ability
so we will all have to become gods
i loe my k100

It seems to be accurate that the rev limiter quicks in at 8000 rpm.
I never had any experience of it, but I know that it exists on the K100.
I am a slow rider too and only went to 200k twice. It was on a highway with no trafic and chainlink fence on the sides to prevent animal (mostly deers) to enter the Highway.

Fuel filter clogged??

Good point Scottie

Hi there another newbie to the block (this site) that is

I own a 90 K100RT which I bought back in 2002. At the time I bought it, it had 182,000klm on the clock.
The previous owner didn't have any prior history on the bike as he had owned it for only 8 months.

Since then I have now just ticked over the 250,000klm mark, albeit a major failure of the spline on the final drive that connects to the rear bevel drive. So at the moment the bike is not doing a great deal until repaired.

Anyway getting back on the topic when I first bought it I started to become acquainted to the balance and handling of this great machine, I noticed it never appeared to be an effort when pulling along uphill whatever, nothing seemed to bother it at all at low revs. I did notice it definitely appeared to want to rev out with noticeable acceleration above 5,6rpm.
I also discovered that the speedos on the RT showed 240kph in comparison to the RS 220kph.
I decided to push the limits a bit further one day on a long stretch of road to see what the bike could do and at 5,600rpm it was like, 'Hello do you want to play' and really opened up and stretched its legs and then some. When the bike hit 8,500rpm the fuel injectors shut off as they are electronically set to run to that rpm. I must say I was stumped when I looked at the speedo to see the needle was up touching the 240 mark
(At that speed I was enjoying symptoms of long range tunnel vision, I found the front end had become quite light but still quite stable, and also my fear the constabulary waiting around the next bend was enough to back it off immediately) I was nethertheless surprised how effortlessly the bike opened up and responded to throttle at the higher revs than under riding speeds.
Even when it got to its top speed it felt like there was still more left in the tank if the injectors hadnt of cut out. I would almost describe it as if the bike had a powerband which under normal riding simply never gets to go near.
As far as how accurate that the actual speed was at that time I cannot say other than since then have noticed that when checked against my gps the speedo indicates 110kph and the gps its showing 109.4kph, which to me is acceptably accurate and is also a good way to check and calibrate any speedo error.

This is assuming a tire circumference of 2100mm. obviously, the tire cir will very depending on speed and wear etc. It should be close, that is what I used to calibrate my speedo on a k75S (130/90/17).

Hi Swells thanks for the breakdown info.

Just a query though I noticed that you have shown at the top of the specs 'K100RT' and that the final drive ratio was 11/32 but you also stated that you used it to calibrate your speedo on a K75S (130/90/17)

I found a post made on the IBMWR website the other day on the Final Drive Ratios which made reference that the final drive ratios on the K bikes. It stated

All rear disk brake non-paralever final drives are interchangeable. Ratios commonly go from 3.2 on a K75 to 3.09, 3.00, 2.91 on a K100RT, to 2.81 on a K100RS. Used units can frequently be had for $300-400. New ring and pinion sets are a lot more, like $700, and labor to install is extra, of course. Note: Early K100s have a different final drive spline design, so a new/used driveshaft may also be required.
The only K75 final drive that WILL required a ring and pinion set to change ratios is the early K75C drum brake unit. These only came in a 3.2 ratio.

So one would assume that the speeds relative to the RPM would be no doubt different depending on the ratio I would think.

Yes, that's right, it's a straight conversion. from the stats shown and I had found for the 100RT shows a 11/32 or 2.91 FD and it uses the same rear tire as the 75S. Unless the crown and pinion has been modified, the FD ratio is stamped on the FD housing. All you have to do is dump your stats in excel and convert rpm to revolutions per hour, reduced by your fifth gear and FD ratio= the number of tire revolutions which then can be converted to a distance per hour. I physically measured my tire and came up with 2.03m. I both measured the circumference and tried a rolling measurement. It is difficult to do alone and not necessary for rpm vs speed, but if you are fine tuning the speedo it might be.

Cop says I was going waay too fast. Officially nailed at 140 in a 100, probably doing about 165K, loved every second of it!

Hi Bruce
Here in Victoria Australia, 140 in a 100 will get you 6 months walkin , anything over 135? i think is 6 months , between 125 and 135 is a month, under 125 is just fines and points yada yada,,

Me and a freind got clocked (2 bikes) at 144 on a beautiful Sat morning on an empty road, Plod was good enough to knock it back to 134 , so only did it for a month, had been 20 years since last loss of licence and plod took that into consideration,

On another occasion in the Northern Territory a few years ago before the 130 speed limit was introduced, I sat my K 100RT on 200 ks for 25 minutes straight, good place to make a mile and it was legal, but not anymore,,

Good luck.