Flywheel weights stock vs SP4

got2dv8

Just thought I would throw out the weights for stock flywheel:

4lbs 1.4oz / 1.854kg

And the SP4 flywheel:

3lbs 2.6oz / 1.434kg

A weight savings of 14.8oz / 420g (that's 70 grams per hole😎 ) ok it's not just the holes as the step is machined out as Marvin pointed out....

Not that much compared to the aftermarket flywheels but significant nonetheless. Any reduction in rotating mass is also a reduction in stress on the motor, not to mention reduces dead weight of the motorcycle itself. I didn't want to go to the extreme with a flywheel right of the bat. Maybe I will want something lighter or I will be happy with this one... only time (a lot of time) will tell.

Robert

griff851

Mine weighs in at at 740g. Definitely gives a snappier response. As for de stressing the motor, well that's debatable. A heavier fly wheel will smooth out the pulses a lot better than a light one.

Griff

marvin

It's not just the holes. They have also machined the floor of it out.

got2dv8

marvin wroteIt's not just the holes. They have also machined the floor of it out.

I just wanted to see if anyone was paying attention...

Robert

marvin

got2dv8 wroteI just wanted to see if anyone was paying attention... Robert

Hard to miss if you've ever machined one down. I take some off of the front rim also (down to the triggers) and a little off of the OD. You can't really take any off of the back rim as there are balancing holes there (unless you re-balance).

996 & Testastretta flywheels are a different story. You can take almost all of it off, leaving just a shell.

BTW, I have an aluminum flywheel for a 916 if anyone needs one (for 1.6 ECU/single phase).

Mr.R

Hi,

Here's a link to a pic' of the one I'm using at the moment it weighs 550g,
I had it dynamically balanced before fitting it.
I also turned down/lightened the standard Strada alternator rotor while I was in there.
Even using a completely standard very heavy 916 crank with 851 'H' section rods it spins up very quickly under load, although this probably has something to do with the lightened primary gear, alloy cam/jack shaft wheels and the seriously lightweight clutch.
I have some Ti' bolts to fix the clutch to the primary gear at some time in the future...
Reasoning that every little bit of weight lost has got to be worth it, or at least trying it and seeing what happens.

I think Jasper's also using one of these flywheels in his SP5.

Steve R

MarkT

Hey-

Here are two pictures of a factory endurance flywheel that is used with a starter. I am going to use it on my '91 Racing since I am going to use a starter since I sold my starter machine. I was lucky to find this one in Germany. It is machined about the same as the one piece Corse flywheel- I have not weighed it but I could if you wish. I have a few one piece Corse flywheels I could also weigh for a baseline of what the factory felt was optimum. I used a "Nichols" version on one track bike and did not like it so I started turning down my stock flywheels. I never milled out holes on them since I did not want to get too far out of balance.

got2dv8

flywheel lightening

Well, my flywheel plan has been shot to hell. I had dropped off my stock flywheel AND the flywheel center (or flange or whatever you want to call it) for lightening. I had not read about anyone doing the center and I figured that would be a good way to shave off some weight also. I was just having them put some equidistant holes (about 18mm or so) in both units. They were charging me 75 bucks....but over a month later and still nothing. So, I stopped by and picked up my flywheel untouched. This guy had done stuff for me in the past, but now I guess he's too big for his britches and does a lot of customized parts. Guess my $75 job wasn't big enough. I would love to do the lightening myself but I don't currently have the equipment. Can a good drill press be used to bore the holes and if so, what type of drill should be used??? I have no hopes of getting a milling machine or anything like that in the near future.

Robert