EDIT 3 April 2018...
Merged a few threads today to consolidate the flywheel stuff.


Figured Id start a thread here in the knowledge forum to talk about and track flywheels lightened, and what users had to say.

I started working on another one today. But this thread is for ALL users, or interested forum members. It's not a sales ad.... If you had a local shop, Rodger Ditchfield or whittled your own flywheel down.. Please post up..
Things like starting weight, did it have balancing holes drilled in the weight? how much and from where was the materiel removed? Did you have a target weight in mind? or just a dimensions to be cut to, and end weight is just a byproduct? Did you have it balanced afterwords? If so where and how much did that cost? Post install usability.. what did you notice after installation?

This is #30 im working best i can tell... I have quotes and emails on three servers, across three different internet forums and hundreds of back and forth emails. Nothing but good things to say about the results.

I'll try and consolidate a bunch of scattered posts to this thread when i get some time.ck it up in the lathe... see what we can cut off it.

 

So far I have i it down to 7lb 13 oz

 

did you measure the diameter before and after? i know the general rule is roughly 1/2" off the diameter but i cant quite remember what that roughly equates to in weight...

by the way nice work.... your hawk will have a hell of a snappy throttle once you get that thing in...

 

It started at about 160mm.. the Rodger Ditchfield spec is 146mm. Im at 145.56mm now.

 

awesome, so heres the real controversial question - to balance or not to balance? I have read atleast a dozen threads on flywheel lightening and it just turns into a jumbled mess of a debate between "roger saying it must be balanced" and "moriwaki saying take a half inch off and slap it on"

 

No idea as I do not have a dynamic balancer at my disposal.. So it's not controversial question at all to me.... I have removed some from the OD, and some from the width, and will run it as is.

 

To me, common sense would dictate that if it was balanced prior to removing some material, it should have maintained it's balance afterwards since the metal is uniformly dense and one side doesn't weigh more than the other.

 

I completely agree

I agree with the moriwaki theory to just slap it on... I dont quite agree with rogers theory that it has to be balanced because it was already balanced and the material being taken off is being removed equally all the way around.. that and the fact that any imbalance will be reduced by both reducing weight and reducing the diameter/circumfrence.

I just know that on every thread Ive read people go back and forth on the balance theory

 

While I do not have experience directly relating to the Superhawk's twin yet, in other powersports I've removed material from the circumference of flywheels without balancing and have not noticed any irratic vibrations or irregularities in crank bearing wear upon tear down. Some of these motors I spin upwards of 12,000rpm. I would run what you have, and keep a watchful eye on the behavior.... but I wouldn't stress about it.

 

In all honesty.. I will say, if it was dynamically balanced before, it's not now...I removed mass from the assembly, and the size, placement, of the balancing adjustment (added or removed weight) in a dynamic balance is located in all three axis. Removing mass, changed that balance.

My point is..... I don't think it's much, Im not convinced the flywheel was dynamically balanced to begin with, and most importantly... I cant do anything about it... So am not worried at all....

It's installed.......... New bars are installed,,,, Im going for a ride.... See Ya.

 

Also, since you are removing material, the percentage of the weight in the flywheel vs the total becomes less, so you are actually effectively reducing the imbalance the more you remove...

So as long as the rest of the stuff is in reasonable balance, a lightened flywheel should in theory maintain it's balance or perhaps even improve on it... Worst case, a very small degradation...

And no, the material is not uniformly dense... That the very reason for balancing in the first place...

 

Roger replied me this, his words in mail:

"There is no need to re-balance the flywheel after you have lightened it
following my info."

I trust him, makes my life easier :-)

Picture of lightened flywheel following Roger´s info

 

I'll see your RD flywheel specs and raise you one.


Again, assuming the flywheel was dynamically balanced from the factory, after cutting material off.. it no longer is...Is anyone still debating THAT point?


If it was only statically balanced in one axis, removing materiel uniformly from the OD,concentrically to the center static balance should be minimally effected.

The RD cut down will effect the OEM balance due to the overall removal of materiel and that it cuts into the OEM balance adjustment points.

Again as tweety pointed out,, it's more of a question.. HOW MUCH does it effect imbalance.. not really if.

I think not enough to matter.... and my first test ride last night supports that theory.

 

+1 E.Marquez & Tweety!
Now, can you give us your feedback on the actual test ride? Did you feel a difference in acceleration and deceleration? Is this really noticeable as a single mod' for the average rider if you can judge that?
Don't get me wrong, not criticizing at all, I'm actually all for it and it is on my list as well. Just want to gauge how much actual noticeable difference you get.

 

Oh believe me, If you take an otherwise 100% stock bike and do only this mod, you are going to feel the difference... No doubt about it... The engine spools up and down so much quicker not having to lug that weight...

 

After the final cut, it's down to 7lb 9 oz
Reduction of 1lb 1 5/8oz

Yes it makes a felt difference.

Would I pay a local machine shop for an hour of labor to do this.. well maybe...but likely not if just for the change on an otherwise stock bike.

But maybe so as it does make a difference you can feel....question is,,,is it a better difference? That only the individual rider can answer for them selves..

 

This is a good point to make... it is snappier, in both good and bad ways. It makes you have to focus on throttle control a bit more and can jerk you around a bit if you become lazy with the right wrist. Personally I really enjoy a lightened flywheel (on an otherwise almost stock motor), but could see if someone wouldn't.

 

You will affect balance anyway, no matter you remove from OD or thickness. I suppose it is dynamically balanced.

But I agree with you, I don´t matter balancing.

 

The flywheel will have some imbalance. the imbalance rotates with the crankshaft. There is no "reversing" stress induced to the crankshaft. The end result will be a small amount of vibration at the rotating speed of the crank. It will most likely not be noticeable and will certainly not damage the engine. The imbalance force is orders of magnitude smaller than the forces applied to the crank by the connecting rods.

 

Thanks for the input, I guess this is jumping couple steps up on my list of upcoming mod's