Is a lightweight flywheel worth it?

[Matt_E]

A flywheel is a storage device for kinetic energy.
On the spool-up, the engine deposits less of its energy into the flywheel and is able to reach RPM faster. But this also means that there is less energy available from the flywheel to put back into the driveline when you let off the throttle.
Practical example: when I let off the throttle on my ski (ATP Total Loss, lightest flywheel on the market), it stops very quickly.
When I get on stock skis, it always takes me far longer to stop, causing me to badly misjudge my stopping distance when I come back to the boat ramp.

 

[SJBrit]

The flywheel also smooths out the engine in between sparks - that's the main purpose of flywheels. An engine is a pulse device - you get two whacks to the crankshaft every revolution, one from each cylinder. The flywheel is there to help smooth things out - to keep the drive train spinning in between pulses. So, as your flywheel gets lighter these things happen:

The engine revs up faster.
The engine revs down faster.
The engine vibration increases.

Most freestylers will sacrifice the second two for the first item, but it is certainly a trade off.

 

[OCD Solutions]

A flywheel is a storage device for kinetic energy.
On the spool-up, the engine deposits less of its energy into the flywheel and is able to reach RPM faster. But this also means that there is less energy available from the flywheel to put back into the driveline when you let off the throttle.
Practical example: when I let off the throttle on my ski (ATP Total Loss, lightest flywheel on the market), it stops very quickly.
When I get on stock skis, it always takes me far longer to stop, causing me to badly misjudge my stopping distance when I come back to the boat ramp.

Great explanation!

The Polaris Octane is a good representation of the opposite side of this topic, being bred for racing, it came with a heavy flywheel where that stored energy was desireable.

 

[kawirydr44]

i want to add in that some dirtbike guys actually put weights on the flywheel to smoothin the powerband on 2 strokes.

I have a tbm flywheel and tbm couplers like i said so ive cut down quite a bit of rotating mass and my ski deff revs a lot faster..... but doesnt have the smooth fallow through power of a heavey stock setup

 

[Melmack]

adamrs80,

First of all, where do you ride? We have several local riders that ride Canyon and the Guadalupe river here in New Braunfels. You should come ride with us sometime. And don't miss the LSFR ride in 1.5 weeks. we have 35+ riders attending.

As far as flywheels go, I was wondering the same thing about Yamaha wheels. My Jetinettics wheel made a dramatic difference on my 550sx but that was a tiny motor with a very heavy stock fw. My buddy BByamaha had his 701 fw lightened. I can't say it made a diference on his. I would do the couplers mentioned above and maybe advance your timing slightly. Be careful advancing timing because it is easy to advance it too much and will cause big problems if you do a lot of high speed runs.

BTW, if your going to lighten anything, lighten your ski. My FX is 30lbs lighter than a SJ and it hits super hard because of it's light weight. I have a milder motor than most but get huge air off wakes because of the skis weight. Look for lightened hoods and poles and make sure your foam is dry. Think light and you'll see more gains in performance for less $$.

 

[adamrs80]

I mostly ride at LBJ. I've got a little girl and another one on the way in July so hopefully I can ride a bit before then.

I think my foam is dry and I really don't want to have to find out. I'd rather just find an FX-1. When I reinforced the tray and installed the footholds it was dry but I understand that it could be wet in other areas. I just don't have time to find out.

I might try a lightweight flywheel on the 550 I'm working on.

 

[Proformance1]

Before I start ripping into my ski for the season, we are going to install and hopefully check the timing on a new TBM 701 charging flywheel. I will have a full review from hopefully a few peps then. It will be a seat of the pants opinion and also a timing light check with an MSD enhancer, to make sure its close to the timing with the stock flywheel.

 

[waxhead]

I would say for for a liteweight flywheel
The lightened ones dont make a huge difference in my experience. however the alloy flywheels have been known to crack

 

[Jetpilot106]

I run the total loss on mine. The down side to it is that the battery doesn't charge. So you have to try and not shut it off all the time. It kind of sucks when your running a bulge also.

 

[Matt_E]

I run the total loss on mine. The down side to it is that the battery doesn't charge. So you have to try and not shut it off all the time. It kind of sucks when your running a bulge also.

With a decent battery, you should be able to run through three tanks of normal riding without running the battery down. Even with bilge pumps running.

 

[Jetpilot106]

With a decent battery, you should be able to run through three tanks of normal riding without running the battery down. Even with bilge pumps running.

Yeah I know. I usually ran the cheap ass Wal Mart battery's. I'm going to invest in something better this year.