Hook up Daytona TT and will tell ya for ya plus get rid of all the crap in-between.
The VOS is nothing more than a timing retard switch

 

 

The tank isn't vented through the cap...on a touring bike it is vented though a hose hooked to this:

A vented cap on a touring bike would be dangerous...because of the compartment around the gas cap...

It would fill with fumes and be quite explosive.

 

What bike? Are you sure your cap is supposed to be vented? Do you have an in line gas filter?

 

The VOES is actually an advance unit. The normal open switch in the VOES allows the timing curve to run up normally through the initial curve. When the switch makes (under light load, hi vacuum) it advances the timing to full advance or 35*. It's all about meeting EPA regulations. On a stock motor it works pretty good but when you start messing with compression it can cause detonation...

 

So this isn't a 'Good Thing©®™'? It's surely good for mpg's and really isn't leaning out the bike if one knows how to adjust the carb...correct?

Or are you saying that removing the VOES really won't make any difference in the power band, mpg's or how it runs? I'm not trying to sound like a smartass, I'm actually very curious to know. If I can get the same mpg's, no difference in the power band, and run just exactly the same as 'with' the thing, I'd love to remove it, as it's just one more expensive piece of something I wouldn't need and couldn't easily afford on a fixed income.

 

No I'm not considering you a smart ***. I always ask if I don't understand... In school most kids in my class hated me cause I always had my hand up... Anyways you have a very logical question, so...

Yes on the first part.. if you get your carb dialed in properly. But you need to remember that timing does make a difference in AFR's . I believe that 1* of timing can make a .2 difference in AFR treading. Bagger and I covered this in a thread a while back.. I might be off with my ratio cause my memory isn't the greatest..

Example: a stock timing curve is running 25* advance at 2800 RPM so if you tipping in the throttle at that 2800 RPM the voes will ground advancing the timing 10* . So if your running say 13.8 AFR at 2800 and then the voes grounds advancing to 35* that 10* of timing advance will actually raise your AFR 2 full points 15.8 and yes that would cause detonation on a high compression motor... That's why I don't bother to use it... How much better mileage are you really going to get. 1-3 mpg? Maybe... Can't really confirm that but you can try a tank of fuel with the voes and a tank of fuel without the voes to confirm for your style of riding..

Part 2: no it's not going to make a difference in power because as soon as you throttle up and vacuum decreases it will break the ground to the voes and revert to the normal timing curve.. remember this as well. The more advance you run the hotter the motor will run. And just so you know I don't believe for tip in cruising you will get the same mileage.. it will drop. How much depends on the way you ride..

Like I said earlier I don't recommend a voes on a built hi compression motor.. Back in the day I was running Accell distributors on my SBC because the stock distributor that had vacuum advance, that was identical to the voes was not good for detonation even then with 98 octane fuel..

 

Oh wait...this is for a 'built' engine? I thought it was for any Harley big twin. I missed the built-up part somewhere, heh. Figures.

Thanks for the information though, settled a lot in my head.