Quote Originally Posted by Ken F View Post
John,
I would have to disagree with him, at least as far as an R bike is concerned. He may be right on a Triumph or Ducatti about the idle part,
but I would strongly disagree about off-stop operation.

The butterfly is closed at idle (as the manual says you should be able to hear them "snap" shut when adjusting cables), and idle is regulated by the BBS.
Off stop, or partially open throttle is controlled by the cables, so yes the balanced setting is important. You want a balanced firing of each cylinder for a smooth running engine.
This is probably more noticeable on a boxer or opposed engine as it is with an upright twin, or even a V design such as the Ducatti. A boxer engine will run with much
less vibration if they are balanced. This is very noticeable in your rear view mirrors.
I will also add that I went from mid 40's to high 40's to low 50's on mpg. (if I ride sensibly, which I don't seem to be able to do most of the time)

Ken
+1. I've got a Harmonizer (sold the Twinmax), and like it a lot.

With only two cylinders, what we're trying to do is get equal power and equal air-to-fuel ratio (AFR). Equal power translates to smoothness (or lack of buzz in the handlebars). Equal AFR translates to a different kind of smoothness, lack of stumbling and "surging". When AFRs are unequal one cylinder's power is less.

For air-balance, we have to use intake manifold vacuum as a proxy for how much air goes into the cylinder and then hope equal manifold vacuum and equal valve operation leads to equal air. If the left to right cam lobe height were different though, the valves would open unequal amounts. Still vacuum and valve gap are the best we have.

Since the Oilheads seem especially sensitive during low power (small throttle angle) cruising, I think balancing vacuum is a good idea although a friend starts there and then tweaks the right hand adjuster for minimum vibration.

So air is the first half of the AFR equation. There are errors of fueling on many bikes greater than the air part of the AFR equation. So how can we balance fueling. 1) Run Techron every so often so the imbalances don't get worse than they come from the factory. 2) Send them out for cleaning and balance testing to verify that the imbalance is small (I don't know the best number but I'd personally like to see less that 2% mismatch).

Because injector mismatch is a statistical problem (some bikes will have a perfect match from the factory and some will be at the mismatch limit, or over time worse), no amount of cleaning will ever get those with mismatched injectors to be balanced and the bike won't run well. Replacement should be considered an option.

The last thing that can be done to eliminate fueling mismatch is to richen the mixture. As you richen the mixture, you consume the small amounts of oxygen that would be left unburned at leaner (stock) AFRs. When you do that, you reach a point, somewhere in the 13s on AFR, that virtually all the oxygen is consumed. At that point, injector imbalance doesn't matter much. My experience is that at around 13.8:1 to 14.1:1 you get a good compromise between better balance and fuel economy.