just machined my flywheel down to 1.5 kg for what you see now. It was 2.488 before. I believe you can go down to 1, but not sure whether that's with the internals removed. Im happy to leave mine as is, if i havent knackered it.??
Fair do's fella. I recently had the engine rebuilt on my 1098R track bike. I enquired about a lightened flywheel during the rebuild. I was informed It'll help spool up a bit quicker but may be a touch more snatchy tapping on the gas. I left it standard as bonkers pick up isn't something missing in the 1098R. Good luck, I'd be interested to hear how you find it. Might go for it next time.
That'll spin up lovely that will, providing you've left the pick ups in place or the only spinning it'll be doing is from the starter motor. I've seen 996RS ones down in the hundreds of grammes. But they don't like ticking over with that little mass. Good job.
Well that's ok then :Facepalm:. I wasn't aware of so many differences until I started buy bits myself, to find they didn't fit, or needed modifying, or, worse of all, needed another 6 different parts to enable fitment.
When i do them i turn the outer ring further down so that it is removed. (Looks like you have about 4mm left)
Tried to find the posts you sent me Andy, remembers the 3mm thing, but got the wrong circumference. Took it back to get re machined after seeing only a 500g loss.
Amongst other work the flywheel on my 1098 SF has just been lightened by 30%. Haven't ridden it yet because the roads are shite. But I have high hopes its going to be feistier than a very feisty thing.
Didn't bother to balance it as I only took material from the circumference, uniformly. When speaking to FE about his approach, he said that he used to have them checked, but the deflection was negligible.
Seems like a great way to lose overall weight, gyroscopic weight, engine inertia etc but if it is so beneficial, why the devil don't they come from the factory like that? Not exactly difficult for Ducati to do, after all. A slightly lumpier tickover seems a small price to pay...
One possibility is loss of engine braking, certainly one of the things I first noticed was the huge engine braking, at least at the time it seemed like it!, when I first rode a Ducati.
I haven't got a slipper clutch and I don't really want one for road riding. I don't want the outlay, the maintenance or the low speed feel and I don't think its strictly necessary on the road unless you're in the habit of clutchless changes and approaching bends in the wrong gear. I'm hoping having a lightened flywheel the tuning work I've had done which has increased static and dynamic compression won't make a slipper clutch any more necessary than it was before.
Lighter flywheel will give more engine braking, because you don't have the momentum of the flywheel to keep it running on.
All you need to know. Courtesy of Shazzam! Why You Have a Flywheel A lightened flywheel is one modification to a street bike that will have more negative than positive effects. I left mine stock. Here’s why. An engine makes the least torque at idle and low rpm, especially when cold (when there are more misfires.) So when you release your clutch a little too fast, the engine torque is too small to overcome the bike's inertia, and it stalls. If you have a flywheel, the stored momentum augments the engine's torque allowing you to use a lower rpm starting-off. Without a flywheel you'd need a higher idle speed, or constantly need to start-off at a higher rpm in order to raise the engine torque output enough to avoid stalling the engine. As you ride at lower rpm in traffic, you are constantly changing between acceleration and deceleration. Engine torque levels are still fairly low at these speeds, so slack in the drive train needs to be smoothed-out with a flywheel. Otherwise, on-off throttle transitions have a jerky effect, giving a less comfortable ride and causing you to use smaller throttle inputs (which is not always easy to do.) At higher speeds a flywheel slows the rate at which an engine rpm changes, so cracking the throttle open or closed results in a smoother transition in torque being applied to the drive train and tires. Again, without a flywheel more careful throttle transitions are needed. The key to faster track times is reduced wheel spin so a light flywheel works against you by making it more difficult to modulate wheel spin, even though it helps lap times by producing more acceleration in the straights. So in effect, a flywheel slows an engine's ability to change rpm producing drive train smoothness and drivability. It also reduces the engine's ability to match it's rpm with the drive train's rpm making it more difficult to downshift without producing wheel-hop. And, when you miss a shift you’ll be glad you have one ... Lightweight Flywheel - Pros and Cons The weight of the stock flywheel is derived by Ducati test riders to provide an overall balance between performance and smooth drive train behavior. That's why Ducati selected the flywheel weight that they did. Did you think that they meant to purposely cripple the bike's performance by using a too-heavy flywheel? When you remove weight from the flywheel (and to a lesser degree, from the clutch) the effect on the engine’s ability to more quickly spin-up is indistinguishable from increasing your engine’s torque (and consequently horsepower) output. But only in neutral. In any other gear, there’s little benefit at all. Obviously, your bike’s ability to accelerate faster through the gears is enhanced by reducing the overall weight of the bike as well as the inertia of rotating components. The crankshaft, pistons and connecting rods, transmission gears, drive chain and sprockets, wheels and tires, clutch and flywheel are all candidates. However, the overall weight of the bike and rider completely overwhelms any reduction of rotational inertia produced by a lighter flywheel. A two pound lighter flywheel on a 600 pound bike-plus-rider will accelerate only 0.3% faster. F=ma. Of course every 0.3% helps a racebike. When you reduce weight you’ll get faster acceleration, and faster lap times - IF - you can modulate your wheel spin driving out of corners. Factory racebikes make so much power, for example, that transmitting the power to the road effectively becomes the limiting factor - so heavier flywheels actually become a benefit. Fear the high-side. The ability of an engine with a lightened flywheel to SPIN-UP more quickly is often pointed-to as a benefit when you bang a downshift and wheel hop is reduced. In this situation, it can be said you have LESS ENGINE BRAKING. However, if your riding “style” makes this an issue, a slipper clutch may be a better alternative than a lightened flywheel; at least that’s what the factory racers think. A lightened flywheel is like a poor man’s slipper clutch in this situation. Conversely, a heavier flywheel will provide more protection for the engine being over-revved in a ham-fisted downshift. The ability of an engine with a lightened flywheel to SPIN-DOWN more quickly is often pointed-to as a benefit if you want the revs to die as fast as possible when you lift the throttle for a corner. In this situation, it can be said you have MORE ENGINE BRAKING. Under normal street riding conditions we tend to prefer less engine braking so we tolerate a less efficient situation where the motor then has to work harder to put more momentum into the flywheel. When racing, you don’t care about storing momentum, you just want to get around the track as fast as possible. This enhanced ability of the engine to spin-up and spin-down also makes it less critical to match engine and drive train rpm for smoother shifts. So, the purpose of the flywheel is to store momentum, reduce vibration and smooth out the loads transmitted to the drive train. It takes energy to first store this momentum, so if the flywheel is lighter it takes less energy and it accelerates up to speed faster. There is an opposite effect when you lift off the throttle and momentum is given up, so the revs drop slower for a heavier flywheel. Because the engine will spin-up more quickly with a lighter flywheel, when you loose traction, modulating the throttle (especially in the rain) will be more difficult. Especially if your throttle position sensor, idle and CO are not adjusted properly. A light flywheel seem to exacerbate a poorly tuned fuel injection system. If you make 100 horsepower it’s less of a issue. Make 130 hp and it will matter a whole lot more. The amount of weight removed from the flywheel and inner hub is proportional to this effect, although if you remove most of the weight from the outer rim area, the effect is stronger. Different after-market manufacturers of flywheels offer different weights and geometry. If lightweight is good, ultra-lightweight is better - just doesn’t apply here. Too light a flywheel can make the bike a handful to ride so a two pound flywheel for the street seems to be a good compromise to preserve some ride-ability. A cold engine runs rough until there’s enough heat to vaporize the fuel, so until then, a lighter flywheel will be less effective in preventing stalls, especially pulling away from a uphill stop. You’ll need to rev the engine a little higher to compensate and you may find it’s a little ornery when running at light loads (3,500 rpm) in the lower gears around town. Often, your idle speed will need to be raised to around 1,300 rpm to help minimize stalling. With all that said, you’ll find plenty of owners that will praise the effects of a lighter flywheel on their bike - but perhaps one that’s different than yours. Not every bike will respond well to a light flywheel, mainly because the flywheel is just part of the overall rotational inertia of the crankshaft, connecting rods and alternator. So, if you have an old alternator SP/SPS with the lighter crankshaft and titanium connecting rods, the effect of removing 1kg from the end of the crank will be very noticeable, because the total mass is much lower to begin with. A non-SP or 2-valve bike has more crank/rod weight, so the effect is less pronounced. For example, on a 916, or any model with a single pick-up and older version alternator, you can just remove the flywheel weight and run the starter clutch hub. Inexpensive, and makes them quite responsive. However, a late-alternator bike with the heavier full-counterweight crankshaft and standard rods has significantly more weight in the alternator assembly and machining the same 1kg from the flywheel will have less of a negative effect, again - due to the higher initial combined mass of the set up. Lightweight Wheels Instead Lightweight wheels don't have the stalling and drivability drawbacks of a lighter flywheel. Also, since the wheels have a much greater rotational inertia than a flywheel, weight reduction here results in a much greater improvement in acceleration (and braking) with an added benefit of reduced gyroscopic forces for improved handling. Lighter front rotors have a similar benefit. There’s even a significant difference in tire weights between brands to consider.
I noticed that too, before I got a 750ss in the early noughties, I had a BMW R80/7 and the difference in engine braking was huge. Can't help wondering why, because you'd think the two engines might have broadly similar characteristics, as a 90 degree twin and a 180 degree twin don't seem so very different. You'd think the desmo system might produce less engine braking if anything... A thought occurs to me, could it be the valve overlap??
