I am sure I'll get slammed by some especially on other forums for voicing what I'm certain to be true but I don't care.
Since this thread is about the truth regarding the single carb mod, I will now recap what I have found to be necessary and maybe dispel some of the myths.
My experience today with skiri's home built plenum and runners. my own builds and trials, and the builds of others have proved some things to me and made it overwhelmingly obvious that the single carb conversion mod has been made more complicated than it actually is.
1. There have been quite a few builds using 1-3/8 and larger runners.........Too large, period.
I am not going to get into using any trickery by inserting "chokes" or "tuned venturi's" into too large runners since any kind of customized or proprietary runner tuning is beyond the abilities of most early Goldwing owners.....and frankly "venturi's" are not needed and have been cleverly used to overwhelm others into thinking they cannot build a working manifold/carb combination without them.
'Chokes'? These are unnecessary with the right size runners which I have found to be 1" to 1-1/4". No larger.
Both 'Chokes' or 'Venturi's' in the runners are not needed.
2. 'Tom's Weber' is an ideal carb for this mod.
I think we all knew this but the reason for this is NOT because "it works perfect out of the box" but because it is very close to proper tune, is easy to rejet, and it's size when turned with electric choke facing forward allows for full auto choke.
Because it is a progressive carb with the same size throats (venturi's) it works very well to mimic the stock throttle pull and twist as well as it's performance.
Granted, Tom's carb will run very good with no changes but the full potential is not realized without doing some simple tuning. This is to be expected of any carb not being used in an application it was not designed for.
3. Heat?
There is a definate improvement to be had by adding heat to the base of the plenum and getting heat to the runners. Any way we can provide heat is a help.
Warm dryer climates/riders will most likely not need heat at all.
Have a look at skiri's build of his custom plenum and runners.
It's an interesting read because it details how it ran with 1-1/2" runners, how he inserted 1" sleeves in those runners from end to end, then how it ran after he sealed those sleeves in.
Also detailed is how we tweaked the jetting a small amount to unleash the power and made a world of difference.