| Author | Message | ||
     Xb9srider |
Has anyone lightened up their rotating mass at all? I installed a lightweight fly wheel on my Ducati 748 and it made a noticeable difference. I was just wondering if anyone has done anything with their XB. Did it make a difference and what did you spend? Ride safe and thanks. Mark  Never Give Up! | ||
| Midknyte |
I installed a lightweight fly wheel on my Ducati 748 and it made a noticeable difference. What difference did it make? | ||
| Djkaplan |
Interesting article by Kevin Cameron just recently in CycleWorld explained how less flywheel weight could actually lower peak horsepower. Not what I would have thought at all... | ||
| Xb9srider |
It allowed the engine to spin up faster. No real horsepower gain, but quicker response to throttle input. I saw someone was selling a lighter something or another for the Buell and was wondering if anyone had tried it. Never Give Up! | ||
| Sgthigg |
So whats the deal with all these lighter crank shafts? Do they also only give quicker engine revs and no HP gain? | ||
| Diablobrian |
faster revs and higher rev limits (in the case of lighter reciprocating components) are the goals. The higher rev limit is desirable because it allows higher hp figures. (assuming equal torque) this is the formula: torque x revs/5252= hp faster revs are desirable on a performance bike for obvious reasons. get up to speed faster. lightening the crank and flywheel cannot in themselves increase HP. The math isn't there. (Message edited by diablobrian on January 05, 2006) | ||
| Xb9srider |
Dunno. I haven't read the article yet. I'll look it up. The Ducati had a noticeable difference in how quickly I could access the power. Prior to the lighter fly wheel, it was a little truck like in revving (way better than a 916/996 though). After the flywheel change, it revved quicker. It wasn't like night and day, but a nice and fun difference. I was just wondering if anyone had tried to lighten their rotating mass on their Buell. Perhaps it's not popular because it is not beneficial. Someone would likely be touting it if it was of great benefit. Never Give Up! | ||
| Diablobrian |
pushrod motors do not have the rev range of the Ducati. The valve train is usually a limiting factor. So, as a result, the reduction in mass is not pursued except in pretty highly modified motors. | ||
| Xb9srider |
Ah! Mystery solved. Makes sense. Thanks. Never Give Up! | ||
| Charlieboy6649 |
Danmit Diablo, there you go proving my 9th grade math teacher right again. I told her I wouldn't need it!  | ||
| Sgthigg |
Gotcha. Learning has occured. Thanks  | ||
| Litng_dave |
Boy you guys have a short memory. On the Ducati motor the flywheel is a bolt-on mass, easily changed, for good or bad. On the Buell/Sportster motor the flywheel is the Crankshaft, which can be lighten by a machine shop, but only after complete disassembly of the motor. Now if you recall back in the later ninties during the age of the "Tubers", specifically the S1's and X1's, the engines were manufactured with basically Sportster crankshafts that had a few pounds ( I think it was around 2 LBs.) removed from their "flywheels" to improve throttle response. As usually Erik is ahead of the curve, and didn't remove too much mass ( as K. Cameron describes)which could have reduced power and hurt driveability. | ||
| Xb9srider |
Righto! Never been inside a Buell motor. Thanks. Never Give Up! | ||
| Diablobrian |
my formula above is actually incorrect.....oops actually it is (torque x rpms)/5252 = HP | ||
| M1combat |
The rotational inertia will overcome the compression easier... I think that's why you "can" get better HP numbers with more mass, but it costs in the area of quick revving. Quick revving is only useful when the clutch is disengaged. It would make throttle blipping more quick. It would ADD engine braking. It would move the usable "putting" range up a hundred RPM or so. The best thing is to reduce the mass of the rods and/or pistons. The problem with that is that we're really limited by stroke length, so none of that REALLY needs to happen until you shorten the stroke so you can at least get to where the valve train is the limit. Or at least that's how I see it... | ||
| Xb9 |
Don't forget about the gyroscopic effect of a rotating mass - wheels, crankshaft, gears. The lighter the rotating mass, the less gyroscopic effect. There's a high speed, high RPM turn at Nelson Ledges called the carousel, and you can really feel the gyro effect of the crankshaft on the Buell compared to say a 600RR.... It makes the bike harder to turn. Hence I'm going to a lightened flywheel and primary drive parts on the 9R track bike I'm building this winter. | ||
| Tommy_k |
XB9srider, It's Trojan that offers the 3lbs lighter crank. Maybe Matt has some experience in actually using one in a built engine. TK | ||
| Xb9srider |
OK, racingmotorcycles.com has a 2 lb. lighter primary crankshaft sprocket pulley. I'm not much of a wrench, but, seems like reducing the rotating mass (inertia) may let it spin up easier. Let's admit it, it spins like a truck. I know it will increase engine braking and I'm OK with that. However, it may also add a twitch to the on/off throttle response I would not be OK with. Mostly, it's academic because it's highly unlikely I will do anything but ride her. Anyway, it's an interesting conversation with alot more response than I thought. Maybe Mr. Buell could chime in or something. I understand he already hotrodded the motor to a great, but reliable degree anyway compared to where it started. Thanks to all. Never Give Up! | ||
| Diablobrian |
Hey, it's winter, what else are we gonna do with all the free time? | ||
| Darkducati |
Horsepower can be gained by weight reduction of the engines rotating assembly by cutting parasitic losses. An average gain of 2.7 hp per pound removed from the engines rotating assembly is normal in automotive applications. This will also affect acceleration. Regardless of horsepower gains, the drivetrain will increase speed faster with less weight present. Whether you will feel the difference is another story. | ||
| M1combat |
I think it may be cheaper to go with a lightweight sprocket and clutch basket... Maybe a lighter front pulley as well. Of course, if you'll have the cases apart anyway I say go for it but be prepared for an increase in engine brakes. |
