So i got my replacement 2nd-hand ignition coil today, to replace the open-circuit 2-3 coil on my K100. Popped her in, and bugger me, I don't need the choke to start her totally cold. She idles straight away! Albeit at 200rpm without choke, but bugger me, she hasn't done that in 6+ years! Used to be, if it was under 800rpm, it was about to die.

Is the ability to idle that crazily low normal on the K100's? It blew me away just now when i started her up! Looking forward to the ride to work tomorrow now!

If the throttles are syncronized it will idle that low but it puts a big strain on the cams and cam drive gear because the cams may want to flick off the lifter ahead of the engine driving them and that makes the back run of the chain slap around.

Since we are discussing TB tuning etc ...the lowest I can go is about 22 on the carbtune and then it is still over 1000rpm but at least all 4 are in line.....furthermore it may be totally unrelated but when I am crusing at around 3000rpm I get a resonance which feels like you are "in sync" with another engine nearby ...ever get that drumming sound/feeling?...anyhow tried to align all 4 with a bit of rpm under its belt and the TB,s were way out and when back at idle they were aligned again...is this also a case of linkage problems? By the way changed the plugs, oil, and filter and back tyre...no the resonance is not the tyre as when I pull the clutch it goes away.

just prepping for the Guyra run and this pops up...bugger

@Rick G wrote:If the throttles are syncronized it will idle that low but it puts a big strain on the cams and cam drive gear because the cams may want to flick off the lifter ahead of the engine driving them and that makes the back run of the chain slap around.

Ahhh, ok - musta done a good job on the last synchronisation I did

@Klompy the grey brick wrote:Since we are discussing TB tuning etc ...the lowest I can go is about 22 on the carbtune and then it is still over 1000rpm but at least all 4 are in line.....furthermore it may be totally unrelated but when I am crusing at around 3000rpm I get a resonance which feels like you are "in sync" with another engine nearby ...ever get that drumming sound/feeling?...anyhow tried to align all 4 with a bit of rpm under its belt and the TB,s were way out and when back at idle they were aligned again...is this also a case of linkage problems? By the way changed the plugs, oil, and filter and back tyre...no the resonance is not the tyre as when I pull the clutch it goes away.

just prepping for the Guyra run and this pops up...bugger

I was talking with Rossco earlier on and he mentioned the drumming.
Many years ago I fitted a pair of new tyres to a car and immediately got a drumming like you speak of and took it back to the guy I got the tyres of as I thought it was comming from them and he came for a drive and said the tyres are causing a dopler.
It was because a different tyre on front to back and the grooves across the tyres were causing some noise but the front tyres were a slightly higher or lower frequency than the back so the dopler effect happened as does it when two bikes are side by side but one may have a worn rear tyre and the other a new one so the engine revs are just that little bit different and the dopler effect comes along and drives you nuts.
Not saying it is that but a good chance.

yes thought so too but when I pull the clutch it dissappears...would be a shame to lose my ME33 lazeretec front as we are quite attached.....

@Klompy the grey brick wrote:yes thought so too but when I pull the clutch it dissappears...would be a shame to lose my ME33 lazeretec front as we are quite attached.....

Oh, I have that 3krpm noise! (Plus the standard 3.5krpm gearbox whine. My car has it too, we're old friends) I often end up pulling the clutch in to see whether it's a patch of noisy bitumen, or 'that bloody noise' has returned. I also have a really annoying vibration around 2500rpm that sounds like my front fairing is about to disintegrate, it's damned distracting!

Why are you using such low rpms on a K bike? It really isn't good for the engine. It is rough on main and rod bearings and risks the detonation that pits the Nikasil near the top of the bore. These engines live longest and give their best service if you float them between 4000 and 7000 rpm.

@Themason wrote:Why are you using such low rpms on a K bike? It really isn't good for the engine. It is rough on main and rod bearings and risks the detonation that pits the Nikasil near the top of the bore. These engines live longest and give their best service if you float them between 4000 and 7000 rpm.

As I said in the first post, I started the bike without the choke, expecting it to die.. But no, it idled at 200rpm! Bloody impressed at the difference the new ignition coil made!

Yes, but we have members talking about cruising around at only three grand. That is too low and is not good for the engine.

Something to keep in mind. When the techs and engineers at BMW tested these bikes, it was always flat out, either on local Autobahns or at the big track in Nardo Italy. They didn't trickle along at low rpm, they were trying to accelerate wear and break things before the bike reached production. To them, a proper rider wouldn't ride their bike at such ridiculously low, in their view, rpms. As a result, such low speed drivability didn't receive much attention. For riding in snow in the German winters, they would unplug the TPS to defeat the closed throttle fuel shut off feature above 2000 rpm and smooth out low rpm throttle response in slippery conditions (with the TPS plugged in and working, there is a surge as rpms decrease below 2000 rpm as the fuel comes back on, and the TPS makes on/off throttle transitions too abrupt to ride the bike on snow as some techs did).

Ohh, sorry, I misunderstood what you were referring to

Yeah, I occasionally have it below 3krpm if I can't be bothered shifting down to first (my gear shift grub screw came loose ages ago, is now fixed, but I now have a 2" permanent slop, until I can find a replacement gear shift shaft somewhere.. - so that 2nd->1st transition is a major pain), and I make sure I'm very light on the throttle when bringing it back up to 3k - you can hear the engine labouring, and I do prefer to keep my bottom end bearings intact!

When out on a 'fun' ride, I tend to keep it in whatever gear keeps me between 3.5-7krpm, as that's the magic range that means I never have to touch the brakes, and never have to shift up or down through corners

Bugger me, the ride to work today was magical! Replacing that dead ignition coil made SUCH a difference! Funny what 4cyls instead of 2 makes! Also impressive that the K100 will still feel so smooth with 2 cylinders :-p

that second coil may well have been working ...erm in a fashion ....but woesomely low in output when it all matters .

good result rendrag ... happy riding !

@Themason wrote:Yes, but we have members talking about cruising around at only three grand. That is too low and is not good for the engine.

Something to keep in mind. When the techs and engineers at BMW tested these bikes, it was always flat out, either on local Autobahns or at the big track in Nardo Italy. They didn't trickle along at low rpm, they were trying to accelerate wear and break things before the bike reached production. To them, a proper rider wouldn't ride their bike at such ridiculously low, in their view, rpms. As a result, such low speed drivability didn't receive much attention. For riding in snow in the German winters, they would unplug the TPS to defeat the closed throttle fuel shut off feature above 2000 rpm and smooth out low rpm throttle response in slippery conditions (with the TPS plugged in and working, there is a surge as rpms decrease below 2000 rpm as the fuel comes back on, and the TPS makes on/off throttle transitions too abrupt to ride the bike on snow as some techs did).

Just because they tested them at high RPM does not mean that we need to ride them in that range. I really don't see why riding at a steady 3000RPM on the road will do any harm at all. I certainly would not recommend that they are ridden under that at high loads but with a light load at steady revs on a flat road I dont believe it would do any harm at all.

Well it does you know Rick. The cylinders are coated thinly and extra low revs does damage it.

You will get a knock on low revs. The Mason is a bit arrogant at times but he is usually right damn it.

Must be his Navy training...! Ajays

Ajays where does what you said contradict what I said.

7000rpm never been there. come to think of it that would be the national limit in 2nd wouldn't it?

@K75cster wrote:7000rpm never been there. come to think of it that would be the national limit in 2nd wouldn't it?

Probably, depending on your diff ratio.. I've gotta ask, you've seriously never been to 7krpm? Fudge, I hit it every day on the way to/from work

One thing I've always loved on the K100, is that it pulls hard all the way to where it's bouncing off the rev limiter in fifth gear. The zzr1100 i had before the K, it would take you 2-3 minutes on a good downhill straight to wring that last 2000rpm out of it in top gear, with the throttle wide open with the stock rear cog.

@Rick G wrote:Ajays where does what you said contradict what I said.

Err Um Err Hmm. It doesn't does it. Can go all day at 3000rpm if it isn't loaded.

But I would drop a cog to accelerate.

Ajays

nope cant recall ever going there, did 4200rpm most days 5000 if shuffling off in a hurry but mostly since using the 2:91 to 1 rt fd its 3850 at the national speed limit so sub 4k and i expect that wont change when back on the road, the boys can order my coffee when they get there and i can drink it without fearing it will burn me hey

I think that if the problem is as bad as was being made out then there would have been Ks going off like a string of fire crackers and BMW would have moved to the moon to escape the irate riders.
The brick engines are a small engine (big for a bike but none the less a small engine) and as such one needs to be mindful that they dont deliver torque like a 454 Chevy so you have to work the gears to get good and satisfactory performance.

short stroke and big overlap on the cam shaft ..these engines were made to rev .

you really should open up that throttle a bit keith ....perhaps in a lower gear ....great power delivery 3-7k and higher mate ....and they were made to do it, else why would they gear it for around 4 k for 100kph .

im still quite surprised that they limited them to 8.5 k rpm (round about)

im sure that these old girls would breath really well right up to 10k or more (with all the right goodies in the valve train , especially in the 4 valve models with low valve mass )..

but with the almost legendary conservatism that bmw are famous for in production vehicles and great selection of production materials (mahle pistons etc ), i guess thats why they last extreemly well .

what ever you do as long as your having fun , but dont load her up too hard at too low a revs mate, they arent a long stroke engine built for max torque at 2k, if memory serves me correctly they were marketed as a high performance vehicle ...in their day .

and fortunatly we get to have lots of fun on what many others call a dinosaur .

I am firmly of the opinion that Rick G is absolutely right, riding at 3000 revs gently trundling around town or highway will do no harm to a K's engine, the K engine is basically a similar size to many small European cars and bigger than a few too. Given the low mass compared to a car and the gear ratio 3K will be fine and as noted above if you want brisk acceleration drop a cog and wind it on.

One point to note is riding around town in low gears at high revs can attract unwanted attention from tax collectors even if you are not speeding. When I lived in the UK it used to be that two or more Police officers simultaneously observing a vehicle and believing it to be exceeding the speed limit could charge the driver (or rider) with speeding even without any electronic confirmation, providing they both estimated the vehicle to be speeding. I am sure their both their notebooks would show complete agreement with their estimate of the speed.
Regards,
K-BIKE

*grin* I can't imagine a K bike attracting police - they're so damned quiet!

@charlie99 wrote:short stroke and big overlap on the cam shaft ..these engines were made to rev .

im still quite surprised that they limited them to 8.5 k rpm (round about)
im sure that these old girls would breath really well right up to 10k or more .

As you know, Chazza, my bike has no rev limiter and I'll sometimes take it quickly to 10,000+ rpm with no issue of valve float. It seems to want to keep climbing. I have held it to that rpm for a minute or more and reached over 245kp/h indicated (150mph), again, still climbing. BTW, the water temp needle doesn't move a whisker North.

Hi TWB,
Most interesting confirmation that they deliberately restricted the performance to comply with the "limit" of 100 bhp. With your uprated breathing and no rev limiter that is great stuff, just goes to show what capabilities lurk within our bikes no wonder they are so reliable, good on you and well done.
Regards,
K-BIKE

@K-BIKE wrote:Hi TWB,
Most interesting confirmation that they deliberately restricted the performance to comply with the "limit" of 100 bhp. With your uprated breathing and no rev limiter that is great stuff, just goes to show what capabilities lurk within our bikes no wonder they are so reliable, good on you and well done.
Regards,
K-BIKE

I would love to, when I get home, get 'er out to a more remote location beyond the black stump where I could really have a sustained go, and presume to not need the air ambulance service should something go horribly wrong. The last speed run I managed was a four to five kilometre straightaway approaching the Mt Kaputar region on Killarney Gap Road, between Narrabri and Bingara, NSW. I began to ponder the thought of snout-down, stubborn wombats, errant 'roos and feral cats under my wheels, but the machine tracked straight and arrow-like with a lovely turbine whine in my ears as she pulled ever harder and higher. I know the speedo is somewhat inaccurate at those speeds with my different-from-stock tyres and wheels, even after setting the speedo calibration with the Karamba software. But perhaps 10 kms optimistic yet reading 250+ km/h is pretty bloody fast for a heavy old girl.

You are right about suicidal wildlife, I recall driving on the road from Alice to Ayers rock and I was going absolutely flat out in a quite powerful rental and coming towards me was another guy who was also shifting and in the distance a dingo was trotting along the road on my side in the same direction as we were going, just before the exact moment the two cars were about to cross the dingo decided to run across the road in front of both of us. Panic braking was done and it made it across without being struck but it frightened the heck out of all of us in our car.

The real danger is a big red, their mass makes them a real killer for car drivers too, a pal of mine hit one which came up over the bonnet and was wedged fortunately backside first in the hole where the windscreen used to be before the big red jumped on board. A passing lorry driver helped by climbing in the drivers side holding the wheel and using both feet to expel it. It bounded away seemingly undamaged which was more than my pal could say for his car.

I look forward to your doing another run when you are back and if you take a gps that will tell you exactly (well nearly exactly) what speed you reach. I know when I have ridden the KRS quickly (on a private track of course ahem!) it was as you say so stable and seemingly effortless, above 130 to 140K it just seems to smooth out and the fairing really works its magic.
Regards,
K-BIKE

Wow 10,000rpm thats kawasaki territory, or the last one I rode was a kwaka 9 so perhaps its not high enough these days, um 70mm I thought was a long stroke compared to the honda's and Kwaka's of 1984 as our engines are undersquare with a 67mmbore. Unless I missunderstood the undersquare, to be bore under stroke. If its the otherway around then let me know so I can stop confusing everybody. Still they go sweetly for the stroke they use. I will have to declare that after 230,000km I am probably just riding around in the sweet spot for me, and it may be when she's back up and running I will find myself hunting the roads at your speeds, afte all they do have a sweet spot up near the 5k mark dont they ? 10,000rpm at 12 the valves may start to lift but then again we dont have an agressive profile on the ramps of the cams and the valves arn't that big or heavy so maybe BMW had things so conservative the redline could be even higher than that.

The run up to Seans was the first real chance to see how the old boy goes (I'm pretty sedate compared to most).Very rare do I go past 120.
Idled along for the most at 100kph on 4000rpm, 110 on 4300,I'm happy with that Sean, did the same both ways.