Good Vibrations

[inanecathode]

I fail to see how sync would change from idle to 1/4 throttle to full throttle opening would be any different if the linkage geometry is correct. Theres no cam action to the throttle linkage, if its set at idle it'll stay set throughout the throttle and rpm range. I dont see how checking sync at a higher rpm would provide any beneficial insight other than basically measuring part throttle vacuum, which is useless information as both cylinders arent in the same tune (different jets). Throttle sync is purely and absolutely for the sole purpose of making sure the throttle valves are angled the same and open at the same time. Vacuum is a coarse signal, if we want to actually get into finer tuning we'd be adjusting fuel jets on the fly (fluid is denser) ;)

You could practically skinny dip in modern carb dip like berrymans, even with the ancient carcinogenic/poisonous/flammable/irradiated carb dip i've left rubber parts and carb pieces in there overnight just for my own curiousity and the worst that happened was the surface of the rubber buna o-ring was slightly slimy (surface layers were starting to dissolve).

[supervision]

 The closer to closed throttle, the higher the manifold vacuum is. That said, maybe 2500 is still full vacuum.  As long as you can match the two, you are running as smooth as possible.  It is madding, to watch the perfect adjustment, change, by locking the nut! Each cly has it's own valve timing, lift, ign timing, as well as carb set-up. If you really want to look at it that closely, these factors, should be corrected, to provide total sync. 

[rhpaw]

The bike has a leak on the throttle shaft. just another lean condition to chase.
How did my numb nuts turn to a carb discussion?

Still... the bike runs better every time I use it. Tonight I tossed on my fixed yics for the hell of it...

[funkamongus]

and........

[rhpaw]

yics?

it's ok, seems torquier down low...
Bike still has issues, thottle control seems more like 'suggestion' than actually a rider controlled input.

We'll work it out.
Putting the full fairings on it tonight too. pop is coming out wednesday night.

[Kid Jedi]

I tune my vision with out the Yics then smack it on after. That seems to give me the best results.

The more threads like this I read the more I want make the fuel injection system for my vision. This bike can be so much more than what she is now. besides, Carbies are so last century!  ;D

[rhpaw]

yeah, the yics was from boredom and whatif.
The carbs aren't tuned to perfection still , I know that. It's not going to be for a while that' they'll be great...

hey, atleast the yics works. I'll plug the tubes in a day probably. not. maybe.

maybe I'll just let AKvision play with it when he comes.

[akvision]

hey, speaking of nuts!  The Beemer "Hanz" is born.   He has all of his.  He started after 15 years of sleep and is moving from the shop to the garage tomarrow.   Bump BumpBump.  I love magnitos!

[funkamongus]

Nice,, welcome back Hanz!!!

[Rick G]

Inane , you are VERY bright and marvelously well informed . The only thing you can't add to the equation, is the experience of all those that I worked with and learned from , not to mention my own experience.
I can't tell you how many carbs I have observed with damaged butterfly shaft seals , from sitting too long in the dip. I have a set of carbs for a '78 XS400 Yamaha, (which , by the way , have a big problem , with plugging up passages, that even long term dipping will not remove, Even with the junk they sell as carb cleaner today.

I occasionally would drop a small part in a 5 gallon dip can and have to fish it out , that stuff would pull a lot of the fat out of my skin and make it itch. hand was super clean tho!

Mechanics I have a lot of respect for arrived at the conclusion that syncing the carbs above idle improved responce. Only 3 or 4 are still alive today, so I can't ask them their opinion now , but I will ask those 4 that are. I'll bet they don't remember much tho, they all left the trade long ago , it doesn't pay very well, compared to other trades.