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Lightened flywheel Balance

Old 10-30-2008, 06:10 PM
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Lightened flywheel Balance

Ok, Sorry to bring this up again but need a bit of help please.

I have read all the posts and did not really find a firm answer on this.

I just had my Flywheel cut down. I went with 1/2" to be safe since this is a street bike with only slight mods. I only had One balancing hole in my flywheel so that was good.

Now that I have cut down my flywheel I want to have it balanced and am having troubles finding a shop that will balance for me. I even called a few specialty shops in the area and no one will touch it. So now im stuck. I can install with out re balancing, Balance my self, or just keep looking. If anyone knows of a good shop please let me know. I have no problem shipping it cross country for a good job.

Has anyone cut down thier flywheel and reinstalled with out re balance? Looking for some advice.

A few pics of my flywheel before and after.











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Old 10-30-2008, 06:42 PM
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I think most had them reinstalled without balancing and the thought was it was a minor concern at most. Question - did you take 1/2 inch off the radius or diameter? Did you check the balance before ? as stock? I don't know that anyone had done that to know how balanced it was in stock form - I never recall reading it and would think that would be telling.
Anyway one of the last posts on this had a long discussion by some good sources with info/opinions on this.
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Old 10-31-2008, 03:45 AM
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I had 1/2" taken off the diameter. I can always go back and take more off at a later time if needed. Should if of been 1/2 off the Radius?

Again, If any one know of a shop that will balance a flywheel please let me know. I am located in Central FL but willing to ship.

Once I find a shop I can also have my stock flywheel checked for balance since no one has had this done yet.
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Old 10-31-2008, 06:51 AM
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My flywheel didn't have any balancing holes. I made sure that it was within .0005 runout, machined it, installed it, and did the sign of the cross over the bike.
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Old 10-31-2008, 06:55 AM
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I had mine re-balanced as part of the machining process (although the machining performed on it by Revolution Racing was somewhat more intricate than shaving off 1/2", and I don't mean that in a condescending way, only that the man who did it had his reasons for doing it otherwise).

Good luck
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Old 10-31-2008, 07:17 AM
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Revolution Racing is overseas it is not? If so. Shipping must have been some $$$.
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Old 10-31-2008, 08:00 AM
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If you install it as is, you will notice no sign of imbalance and it won't hurt a thing.

I promise.
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Old 10-31-2008, 08:13 AM
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Originally Posted by mikstr View Post
I had mine re-balanced as part of the machining process (although the machining performed on it by Revolution Racing was somewhat more intricate than shaving off 1/2", and I don't mean that in a condescending way, only that the man who did it had his reasons for doing it otherwise).

Good luck
Do you have any pics of yours after it was done? can you describe what made it intricate?

thanks
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Old 10-31-2008, 08:51 AM
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Has anyone shave more then 1/2" off the diameter?

I could actually shave off the balancing hole and still be under abour 11/16" total. I only went 1/2" since that seemed to be what everyone talked about.
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Old 10-31-2008, 10:42 AM
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Revolution Racing is indeed in the UK and shipping cost me dearly. That being said, I bought a used flywheel (in the UK) on eBay and had it shipped directly to Roger. He did his magic, had it balanced and shipped it to me. If you e-mail him, he will send you the prints detailed exactly what needs to be done.
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Old 10-31-2008, 10:46 AM
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Who did the work for you and how much did it cost? I'm about to do mine and I think I'm going to take a bit more off than 1/2". After some comments by autoteach and some discussion here and with my local mechanic (and looking at boxes of other motorcycle flywheels), I think it's safe to remove quite a bit more than 1/2".

Last edited by killer5280; 10-31-2008 at 10:59 AM.
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Old 10-31-2008, 11:44 AM
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check this place out:
http://www.procycle-online.com/main/...lightening.htm

i called them and they said they can do it. they will take off as much as they can or whatever you specify. the price listed is for a ttr125($55/including return shipping.) they said it might be a little more for the superhawk but, they'll have to see it first. i'm prob. gonna try them.
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Old 10-31-2008, 01:16 PM
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I ran across that website awhile back when searching around for information on flywheel lightening. They sure took a bunch off the flywheel pictured. I'm sure somebody local can do it for me without having to ship it off, but I just haven't taken the time to find someone.
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Old 10-31-2008, 01:36 PM
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No need to make a science project out of it.

Chuck it up.
Turn it down (1/2" off the dia. works).
Put it on.
Call it good.
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Old 10-31-2008, 01:42 PM
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The chance of imbalance reduces as you reduce the amount of material and the significance of imbalance reduces as you reduce the amount of material... Facts...

I'm with RCVTR... don't over complicate it...
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Old 10-31-2008, 03:07 PM
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I don't want this to get too long winded (again), but I have one more thing to add.

the main reason for machining the flywheel is to reduce the polar moment of inertia (mass resistance to angular acceleartion). Taking material off the outside diameter is by far, the fastest way to accomplish this. Machining material off anywhere else has far less effect on the polar moment. It makes it lighter, but does not have the same effect on the rate of angular acceleration.

My friend that builds and tests things tried taking more off - granted, he lightened the crank and used Carillo rods, as well - found that excessive lightening of the flywheel starts negatively effecting the ability to put power to the ground, because the rear tire has a tendency to spin.

It's probably ok to go further with a stock, or mildly built engine. I was plenty happy with 1/2" off the OD.
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Old 10-31-2008, 04:00 PM
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FYI I called the guys at the site
http://www.procycle-online.com/main/...lightening.htm

They will cut down your flywheel but no balance.

I have decided. I am going to have my guy cut my FW down some more = 3/4" total just for S&G.

FYI "My Flywheel"
6.05" Before Cut.
5.55" After 1/2" cut off.
5.30" After 3/4" Total.

I will weight my FW after my final cut. Then will also weight and measure my stock FW when pull it off my bike.

Once I find a shop to balance my Flywheel I send both the stock and the cut down Flywheel and post the numbers.
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Old 11-01-2008, 01:43 PM
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I took alot of material off my Ducati flywheel and loved it. Its still no where as light as the aftermarket ones but i could tell a difference.

Since the vtr is going to be more of an around town, stop and go, hooligan machine i doubt ill lighten it any.

I like having the extra enertia pulling away from stop lights.

Having a lathe helps though, you can always remove more till you find your own personal sweet spot.
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Old 11-02-2008, 12:19 PM
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I think I took about 1/2" off the radius. I believe I only had only .200 of the stepped edge left before I go to the starter sprague clutch area if that makes any sense.
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Old 11-04-2008, 02:42 AM
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Originally Posted by mikstr View Post
Revolution Racing is indeed in the UK and shipping cost me dearly. That being said, I bought a used flywheel (in the UK) on eBay and had it shipped directly to Roger. He did his magic, had it balanced and shipped it to me. If you e-mail him, he will send you the prints detailed exactly what needs to be done.

I'd pay close attention to what Roger does. He knows more about the VTR's himself than we do collectively. I agree, no need to make this a science project. Finding out how the crank fails due to second order vibrations is not something that I want to demonstrate.

Darylward - did you check with local machine shops? I'm talking about regular job shops that don't have anything to do with cars or motorcycles. It's commonplace for these shops to have balancing equipment and most would love to help you out. Make a few phone calls and I'll bet you find one in your area.
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Old 11-04-2008, 06:39 AM
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If you really want to get technical about the whole thing, you should have your entire rotating assembly balanced. The flywheel plays a role in that, and if you don't balance that as well, then you may be missing the boat. So, pull the crank, connecting rods and pistons and get it all done together. Or you could be like myself and come to the conclusion "that is too much work". Is balance important, YES. My flywheel had NO balance holes. One would have to assume that it was perfectly balanced at that point. I machined to within .0005 for accuracy. I wouls assume that my balance wouldn't change much from that, but what we found was that with our static wheel balncer, no matter how many times we tried checking for balance, it always rotated to a different spot. We would put what we thought was the heavy spot to the top, and it wouldn't rotate down all the way, so we would put it at another location, and it wouldn't rotate down all the way. Eventually we at eleventeen different "heavy" spots and no conclusion, except that the imbalance was negligible and that if there was a problem, it would be a good reason to rebuild with some better components. Minus the possibility that the crank breaks and splits the cases in two+ directions. If you have a balance hole or holes, than I would suggest checking the balance afterwards. if you find one heavy spot, than fix that issue. Otherwise I would just run it.

On a serious note, this increases HP, not TQ. I have a hard time getting it up now, but when I hit about 6k it wants to go forward which was the desired result. You will notice that riding twisties hard will become alot harder, and will require much more concentration on the twist grip. But, there will be few 600's that can keep with you coming out of turns.
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Old 11-04-2008, 07:59 AM
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Originally Posted by autoteach View Post
On a serious note, this increases HP, not TQ. I have a hard time getting it up now, but when I hit about 6k it wants to go forward which was the desired result. You will notice that riding twisties hard will become alot harder, and will require much more concentration on the twist grip. But, there will be few 600's that can keep with you coming out of turns.

why would riding twisties be harder? less traction?
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Old 11-04-2008, 08:09 AM
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less rotational mass,so you lose revs faster.
bike will feel peakier,will slow up quicker when you let off the throttle.
if your not smooth with the throttle it would prob feel like a rocking horse.
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Old 11-04-2008, 12:51 PM
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wow thats wild. we cut the can on mine and left the back ring the stock size.

stock the balance on the flywheel is not great. and stock mine had like .03 runnout. we trued it what we could while cutting it. cut what we could off the can. and bolted it back up.

im running with no bar ends and billet foot pegs and theres no more vibration then there was with the stock uncut flywheel.
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Old 11-04-2008, 12:56 PM
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Originally Posted by hawxter996 View Post
less rotational mass,so you lose revs faster.
bike will feel peakier,will slow up quicker when you let off the throttle.
if your not smooth with the throttle it would prob feel like a rocking horse.
to me it makes the bike easier to ride, even in tight areas. you can use the engine more for speeding up and slowing down so you dont have to rely on the breaks as much.

i dont think ive touched the rear break pedal since scrubbing the flywheel down.
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Old 11-04-2008, 01:55 PM
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What hawxter said, and it is very touchy. It will push wide easily, and I can slide the rear on command, I just refuse to command it to do so. Trust me, this is not for the faint of heart, there is a reason that the big dogs have slippers. If you are a good rider, then you will benefit, otherwise leave it and enjoy another of japans great motorcycles
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Old 11-04-2008, 02:56 PM
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Originally Posted by hawxter996 View Post
less rotational mass,so you lose revs faster.
bike will feel peakier,will slow up quicker when you let off the throttle.
if your not smooth with the throttle it would prob feel like a rocking horse.



doh!

im wrong here when you let off the throttle it will not slow down quicker.
it will be more like a 2 stroke with little flywheel effect.
in other words in the tight stuff you will use your brakes more often.
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Old 11-04-2008, 03:31 PM
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It will have more engine braking with a lightened flywheel. You were right the first time. Because it won't have as much flywheel inertia keeping the engine spinning it will drop revs faster.
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Old 11-04-2008, 03:58 PM
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yes you increase engine breaking by lightening the flywheel, most people think its the opposite.
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Old 11-04-2008, 04:17 PM
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Originally Posted by killer5280 View Post
It will have more engine braking with a lightened flywheel. You were right the first time. Because it won't have as much flywheel inertia keeping the engine spinning it will drop revs faster.

yeah thats right!,my head has been killing me all day.
think its time to go to sleep and refresh.
been a tough day.thought process is fried gnite all.
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