Finally did my flywheel. Since I put it back on I have only ridden about half an hour due to freezing my ass off. The differences are subtler than I had hoped. I didn't have any trouble pulling away from a stop and the low end power seems about the same as before. Overall it seems a bit smoother and revs a bit quicker, but it's certainly not a night and day difference, although I didn't get a chance to really ride it hard. I'll give another report when the weather warms up and I have a chance to evaluate the changes more thoroughly.
The before weight was 8lbs. 12 oz. and the after weight is 7 lbs. 5 oz., for a weight reduction of 1 lb. 7 oz. Just for kicks, I took one full inch off the diameter. I did not have it balanced after the machining.

when you did this, do you disassemble the flywheel from the rest of the rotor? or is that even possible? I haven't looked at it closely before and its mounted on the bike currently.

The guy who machined mine left it attached. I didn't really look at removing it either.

You really cant remove it. The other issue is that the stator basket isn't really round. so getting that so that it has no radial and axial runout is a pain. You either need a four jaw or shims.

thanks both, glad i asked.

will be anxious to hear longer term impressions with the full 1inch off, and any effect on engine braking, stalling, etc

I separated the flywheel and alternator rotor. I marked the orientation, so it would go back the same way. I used red Loctite to put is back together. Separating them gave me a good purchase in the lathe. I used a 3 jaw chuck and bored some aluminum soft jaws, then checked runout with a dial indicator.

I believe that the flat torque of the VTR engine masks the improvement. It doesn't change the basic torque characteristic of the engine, so the improvement is not immediately noticable. It's there, though. I felt the same way at first about a heavily modified engine, because the basic character was wery similar, but soon realized there was more torque everywhere.

You can remove the starter sprague, but I thought that you can remove the weight from the basket. I must be thinking incorrect. I have done flywheels on a 125TTr, a yamaha 440srx, and the superhawk... can't remember what they all took to do.

I think the basket comes off when you remove the sprague. The bolts go through the basket and flywheel and thread in to the sprague carrier.

Ok.

Sorry about the late reply but I was unavailable the past few weeks.

Here is the VTR FlyWheel Mod Roger Ditchfield from http://www.revolutionuk.co.uk


http://users.fdn.com/~dward/SuperHaw...Flywheel-1.pdf

My image did not load

can you down load the PDF under the following link.

http://users.fdn.com/~dward/SuperHaw...Flywheel-1.pdf

That worked!

Bumping an old thread. I am curious what the consensus is for how much to remove? Should I remove 1/2" from the diameter or radius?

The general rule of thumb around here is to remove 1/2" from the diameter. Just for fun I had 1/2" removed from the radius. I have been living with this for about a year now and have to say that this is a great mod. The engine revs much quicker and is just much more lively and eager (if that makes any sense). Driveability has not suffered; it is not hard to pull away from a stop or anything like that. The lightened flywheel just helps everywhere. I think you could take more off without a problem.

How many miles have you put on that modified flywheel? I know there was a lot of discussion back and forth, but for me the proof is in the pudding.

I would guess 2-3000 miles. My initial impressions were that the effects were fairly subtle, but now I think that the engine is just much more responsive and eager to rev. Well worth the minimal effort and cost.

So has anyone done a 1/2" versus 1" removed comparison?

I doubt it. It's not that critical, but the lightened flywheel does make a noticeable and positive difference in the responsiveness of the engine. Like I said, I think you could remove more than 1" (from the diameter) and still see the benefits without negatives.

Well I know a lightened flywheel has benefits, but I am curious at what point you start seeing negative effects.

So I read up on the advantages of a heavy flywheel, because Honda isn't stupid and just slapped a giant metal thing in there, and found that it is better for drive-ability and better gas mileage. The last two are actually related, because the larger flywheel has more momentum. When you release the throttle on a lighter flywheel, you will have very rapid deceleration, even if you barely let go.

The advantage is that you rev up quicker, but you get a twitchier throttle, and possibly worse gas mileage(do we actually give a shit though?)

A flywheel is merely an energy storage device. Lightening the flywheel on the Super Hawk makes the engine more responsive and doesn't hurt driveability. Can the performance increase be measured? Probably not. It just makes the Hawk sportier and "funner."
Gas mileage? I don't care.

Gas mileage?

It's crap in stock form... Ridiculous once you jet the thing spot on and laughable once you do anything to the engine...

I put mine in the same scrap pile of unused parts where I put the crappy front suspension and barely discernable stock headlight...;)

If you do 1/2" it won't hurt driveability... Honda made the VTR to be an allround and beginners bike... Basicly they made it mediokre so squids wouldn't hurt themselfes... To make it undriveable or "twitchy" you'd have to go to far more drastic measures...

So anyone have a flywheel they don't need? I wanna experiment with 1/2" versus 1" removed.

That looks a little bit like what I did. I did notice that I cannot lug gears in town without it "knocking" the chain on power strokes. Maybe that is me, but it seems like it needs to be at 3k rpm or better.

I gave another review today after living with it for most of a year. It really does make the bike livelier and more fun. I haven't noticed the lugging thing, but I don't do that very much anyway; I like to keep it spinning a bit.

I have a lightened flywheel also, although I cannot remember by how much. No problem with low down flywheel effect at all. Still plenty of low down grunt.

Flywheel mod from Roger @ Revolution
 

Roger from Revolution mentioned in a mail to the UK VTR list that the incorrect flywheel mod diagram had been posted here on the forum, I'm assuming this thread was where it had been placed. I'm attaching his corrected file, and I'll check for cross postings.

Cheers!

I just find it funny that i tried to get some information on this from Rodger around 2 years ago and he wouldn't give it to me. He said he was tired of his stuff getting posted to the internet......

Guess he just hates Americans..... :rolleyes:

I wonder if this is what he might be tired of though - someone posting something with the wrong numbers, or misquoting him?

He's always been very helpful to the folks on the UK list, and guys that have had him work on their bikes have been very pleased with his work. If he wasn't across the pond I'd definitely throw some business his way.

All I can say is he told me he was tired of giving people information only to see it later posted on the internet.

So I just give my $$ to Mister Kyle who is not only close but has always been more than helpful to me.

8541Hawk: Roger sent me same diagram week ago but I wouldn´t post it on internet as there is Courtesy of Roger Ditchfield written. Maybe he don´t mind but ...

Anyway he wrote me that balancing is not needed when done properly.