I wrote a long explanation but the forum logged me out and I lost it. I was also going to recommend Truett and Osborn "Torque Monster" flywheels.

Trueing and balancing are two separate things;

Imagine a cart with two bicycle side by side. Now imagine one or both of the wheels are buckled or leaning into each other. What's going to happen? You're going to end up with a side to side waddle (vibration) which is also going to have the ends of the shafts vibrating up and down wearing the bushes and bearings.

Getting them parallel is trueing the crank.

Balancing is the same as what you do to your wheels/tires. If you have a heavy spot in one place and you're going to end up having an up and down vibration at that point. At one end of the seesaw, you have the heavy side of the flywheel, at the other end you have your conrod, pistons, pins etc. Balancing equalizes the two so that the inertia of the pistons rising and falling is counter balanced.

For example, a 1/4 oz imbalance will generate a force of about 7 lbs at 2,000 rpm but at 8,000 rpm it would grow to 114 lbs of force.

It's done by adding or subtracting weight according to the combined weight of the parts and according to a formula for what effect you want, e.g. low end torque and smoothness versus the speed of increasing RPM (for high HP engines). This formula is expressed as a percentage, e.g. 52 ... 60 ... 70% balance factor.

Phil Irvine, the guy who designed the Vincents used to say 67% was best for a V-Twin but with H-Ds, it's generally always set at 60%. However, speak to an expert like T&O and ask them. Changing it will alter the characteristics increasing or decreasing vibration and where it lands.

If you stick with a standard stroke (a stroker is likely to vibrate more), Truett and Osborn "Torque Monster" flywheels might suit you for lower RPM riding. The extra weight should smooth the engine out a bit (dampening the vibes) and make it *feel* like it is torquier due to the increased inertia. They make a good compromise ... a 4.5" 87ci flywheel.

(As an aside, down in Australia, they are still making Vincent engines and from what is basically a 1300cc 1930s design, they are getting 135 BHP at 6500 RPM, and 113 ft lb at 5500 RPM).

 

Iv'e looked over Truett & Osborns website and they look like they do some excellent work, unfortunately it's a bit out of my budget. I'm beginning to wonder if I should even mess with the bottom end. I would like to get the bottom end done though. I'm still curious about Revolution Performance because their pricing is more in my budget. I haven't even touched the motor yet and I'm getting a headache!!!

 

I cannot see where T&O price just trueing and balancing a crank. How much were they?

You would not want to buy a complete new crankshaft. You don't even need to buy new flywheels, unless you want to go Stroker/Torque Monster ($425/475). I'd call them and see. There's a lesson on the advantages of more interia, here.

Can you take the crank out yourself? I mean, I am sure you can break it all down to the crank in one side of the case, all you need then is access to a small press to get it out.

Putting it back in takes a little more care but you could just pay to have the bottom end re-assembled with a fixed crank by a local shop. The shims *should* be the same as the ones that came with it but you'd need to know to check. The rest you could do yourself.

Short answer was, you want it trued and balanced.

 

I agree that heavier flywheels would be better for our application. Never split Harley cases before, I'm sure I could do it but if I could find a place that I could send it to, remove the crank, do the true and balance then reassemble it that would help.

 

It's no time or effort to split, therefore it would not add to costs, and not a lot extra in shipping, so I'd say that was a good idea ... unless you need to prepare the cases first, e.g. strip or blast them. But I know T&O do their own blasting, so that's a possiblity too.

I wanted to "dress" mine; strip them using thinners, remove some bad corrosion, marry the cases so the castings matched better first ... stuff I would not trust a shop to get it how I wanted, nor want to pay for them to do/mess up ... so I split the cases myself.

Those are a) the easy, and b) the time consuming parts.

Setting the clearances on the crank requires a shim which should not change if just trueing and balancing. You should be OK but I would understand why you would want to send it out, e.g. to get the shimming right. Again, it's not a lot of work timewise so it should not cost much.

This is a video of how not to do it ... (They drop the crank, not catch it!).


(Part two is reassembly).

 

Shimming ...

 

Going back to the vibration, I bought a new '03 TC88 Dyna and that had an unfortunate vibration patch from new. So IMHO there is a 'feature' about that model that is probably down to the unusual rubber mounts. My bike was sort of OK, but needed a bit more go, so I installed a 21T compensator, to replace the 25T stock one. That cured it! The vibration patch was moved down the road speed scale and, by using higher revs at normal road speeds, the bike was greatly improved. The vibration was still there, but not as irksome or intrusive.

As for long stroke conversions increasing vibration, that is not my experience. I had my Evo stroked, using a JIMS stroker kit, which was smoother running than the stock engine, despite cams and higher CR. So while the theory may suggest one thing, a skillfully built engine can be quite the opposite! I would have no qualms in doing that again. We can see videos above of a hand-built engine which, by definition, will be assembled to a higher standard than a factory built engine.

 

We've built/re-built over 500 Evo/Shovel/Pan/Evo XL/IronXL/Flathead crankshaft assemblys over the years.
Straightforward work.
Balancing helps them dramatically.
Knife-edgeing, lightening, smaller diameters, lightweight H-beam rods, etc.
Scott

 

What difference or how much does knife-edgeing and other lightening make to them?

Technically, I understand but not practically related to an H-D Big Twin.

Am I right to say the stock flywheels are pretty close in weight to the T&O TorqueMasters, but that the S&S wheels are generally lighter?

Thanks

 

Thanks for the videos, they were quite informative. This being my first build I feel it would be better to let someone with more experience handle my crankshaft/lower end work. Not to sound like a broken record but I'm still waiting to hear from anyone about Revolution. I'm still going to try and locate someone in Georgia that provides the crank work I'm looking for. Not doing the stroker this time, going to keep it stock in that area. I appreciate all your comments, keep'em coming. Thanks again.