Balancing a Crank

[STN]

I was wondering if any of you guys have had your crankshafts dynamically balanced? I'm thinking about getting it done myself, you know getting the micropolish, weight reduction, and balance. But I'm wondering if any of you guys have had it done, and how much weight did it take off?

[Freestyle72]

My crank is balance. Can I tell a difference between a balanced one and not? Not really.

[yamaha_george]

My crank is balance. Can I tell a difference between a balanced one and not? Not really.

FS72,
you may not "Feel" the difference but the engine does. the lag on rev up will be quicker (we are talking nano / milli seconds ) the engine will drop revs quicker as you get off the gas ( your backside does have to be sensitive enough to feel that and some riders can.)

what does it do for your engine:- less mass it will work more efficiently (MPG should go up a tad) polishing gives less drag BUT less oil retention on the surface so you oil pump needs to be at its best. Balancing the whole crankshaft/con rods/ pistons to 0.1 of a gram across all 4 will seriously reduce "the hammering" the engine takes whilst working.
The engine will climb to redline that much faster.

Is it worth the cost? if you drag race / race period or intend to leave the bike in first class order to the grand kids.....YUP.

[China_Racer_1]

Ok Ihave experiance with this.

I echo what yamaha George jsut posted.

I had my YZF engiens crank balanced polished and reduced teh weight.

The engine seemed to spin a bit easier and I did not feel much more than a very smooth engine that was right on when it came to turning up the throttle.

Racecranks.com I think are who spyder used for mine. However it too them FOREVER to get mine done due to the weight reduction I wanted to due.

You might want to confirm a lead time before you send them yours.

Again I think it made a fair enoug hdifferance that I would not build a race bike again with out doign this if it was a ground up build. Or if I was serious about racing in any respect. the roll on was just so noticably smoother and right on.

[ragedigital]

I was wondering if any of you guys have had your crankshafts dynamically balanced? I'm thinking about getting it done myself... and how much weight did it take off?

I guess the real question is - why are you wanting to do it? I would imagine the cost is pretty high for such an operation, not to mention the time to tear down the entire bike to get to the crank.

[thatkid]

The pros and cons are detailed in the wiki http://fzronline.com/wiki/doku.php?id=e ... _explained

If some company took forever to complete the task, I would say they are well........ SHIT and don't know what they are doing.

Yes I have experience with lightened/balanced cranks, a work mate (his daddy was a millionaire) use to race Formula Ford, after every race daddy paid for a full engine strip down rebalance E.T.C. We used to tear the engine down, the re-balance was done by the machinists in days. Daddies boy never won anything tho

One time he never even qualified, him and his dumb mate had recently replaced the throttle cable (unknown to me) we went to Donnington, after he failed to qualify he said "there's just no power @ WOT" his mate said "there should be, we just replaced the throttle cable" Yes the dumb shits couldn't even adjust that properly, Pedal to the floor the twin choke Weber's butterflies were 3/4 open.

EDIT: IMO the flywheel should be on the crank when it's balanced, but I could be wrong.

[STN]

I'm figuring on doing some racing next season, as I work at a motorcycle shop I can get things done fairly quickly, but I was just wondering what these engines in particular get out of a good machining. Thanks guys, and I found a local guy who can do the work for about 300 bucks he said, thats polish, weight reduction, and dynamic balance.

[yamaha_george]

I'm figuring on doing some racing next season, as I work at a motorcycle shop I can get things done fairly quickly, but I was just wondering what these engines in particular get out of a good machining. Thanks guys, and I found a local guy who can do the work for about 300 bucks he said, thats polish, weight reduction, and dynamic balance.

STN,
That seems about right dollar for dollar it is roughly what I charged to do weight reduction,balancing & polishing when i had the shop.

[China_Racer_1]

Anyone want a lightened and balanced YZF crank

It has somes light damage from the rod busting but I think a small weld grind and reblamce would be pretty simple to get this brought back up to snuff.

I should have it out of the cases this week to do a formal inspeciton on it.

Let me get it out and take a good look at it then I can post if it is worth salvaging.

If I had the money to rebuild my engine I would reuse it based of what I have seen so far but again I need to pen her up and pull it out for a real good look before I commit.

[gogofizzpow]

pmd