Odd things to me.
Why is the Oil window on the opposite side of the oil fill?
Why does the rear tire hugger have a cut out hole in it?
What exactly is the overrun fuel cutoff?
The oil window placement is to keep the foaming of the oil in the window at a minimum. Or, BMW engineers just wanted to make you get up and walk around the bike to check the oil level as you fill it during an oil change.
The Rear Hugger has a hole due to a low pressure area that formed during high speed runs of the rear tire turning so fast. That low pressure area caused the tire to deform and shake.
I guess you see Overrun Fuel Cutoff in RCK3. This cuts the fuel at the injectors to keep from hydro locking a cylinder on over rev of the engine banging the RPM limit during those high speed runs that deform the rear tire.
My guess at these questions is:
The Rear Hugger has a hole due to a low pressure area that formed during high speed runs of the rear tire turning so fast. That low pressure area caused the tire to deform and shake.
Ok, that's my 2 pennies.
Sorry, I have to totally disagree with this. The tire is WAY stiffer than that thin, flimsy "hugger". So if there was a low pressure area there, that would deform WAY before the tire would. In fact, there's no way there would ever be enough of a pressure delta to do anything, there's a huge air gap around the tire with a far larger area than that small hole. I've never even heard that particular theory before, and since no other bike I can think of has it, I think we can myth bust that. What it looks like is that it's simply a clearance hole for when the rear suspension is totally compressed, to prevent it from hitting that pointy part in the inner fender that sticks out.
Thanx!
It states the overrun fuel cutoff is switched off at engine speeds greater then 4000rpm in slick mode, but activated in other modes like rain, sport and race.Trying to figure out what exactly is this feature.
Overrun is when you shut the throttle, but the engine is still spinning and not doing any work. The drivetrain is however keeping the engine spinning.
Overrun cutoff is shutting the fuel off during overrun.
Deactivating the overrun cutoff keeps some fuel running to the injectors even though the rider has shut the throttle. This decreases engine braking. The added fuel helps cool the engine and control temperatures. It also makes a sudden throttle on smoother. And makes race cars shoot flames out of the exhaust on throttle off.
The fuel will automatically be turned back on when RPM drops to around 1,000 RPM over idle speed.
Summary:
Overrun cutoff active = more engine braking.
Overrun cutoff deactivated = less engine braking.
Unlike Ducati's system, BMW does not allow us to tune in the amount of engine braking we would like (stock bike). There is just the "normal" setting and the overrun cutoff setting. For no engine braking, more fuel needs to be added so that the engine spins on its own without relying on the driveline, but is yet not accelerating.
Elk,
Thanx for that info! I was trying to figure out exactly what it does and you explained it.
I have never had a bike that had a hole in the rear huger and never had a bike that had the oil window on the opposite side of where you put the oil in. Very strange German stuff I must say.
I have my wife watch the window as I put in the oil. It makes for an interesting discussion. I SAID MORE - NO WAIT NOT THAT MUCH. TAKE IT OUT TAKE IT OUT. The neighbours must wonder.
As far as I know the hole in rear tire huger is to have room for ABS pump if one bottoms out. This happens especially on 2up rides. So babes over 120lbs 2up is a no especially on bumps >
That hole is there to allow gravel to fling onto the undertail and dent it, so it doesn't recirculate back under the front of the tire and create an endless loop of the same gravel circulating under the tire, over and over. Brilliant, actually...
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