Throttle Valve Shaft Seals

[The Prophet of Doom]

Probably - I tend to do that.
Actually I don't care to much as long as it goes well.  I'll try both ways and stick with the one I like the best
It's only a 1/2 hour job

[Rick G]

No , Rikugun , not every one else , just you !

[pullshocks]

Looking forward to your results Roro.  If you wouldn't mind noting down your EGA readings, that would be most interesting.

Also, will your engine idle with both throttle plates completely closed?(I.e. idle knob completely backed off and sync rod disconnected? ) If yes, what RPM?

[admin]

  um Guys, I am going to have to ask everyone to tone down the personal comments.
  let's keep this amicable.
  we don't have to agree 100% on each and every minute detail.
  carburetors are your friends...

  that is all.
 
   --Admin

[Rikugun]

Admin - PM sent.

[Rikugun]

Not an issue with my metal stick manometer :-)

How does this work? Is this store bought or something anyone can make at home?

I'll try both ways and stick with the one I like the best  It's only a 1/2 hour job

That seems like a very reasonable course of action.  :)

Regarding your proposed balancing regimen using EGA to optimize mixture settings, does the process start with the assumption the plates are more or less even or is that not critical initially?

[Jimustanguitar]

I bought one of the real Motion Pro sync sticks a year ago, and it blows my homemade sync tool away. If you can swing the cash, I definitely recommend buying the real tool!

If you're friends with a service shop, usually they're happy to let you use theirs for a couple of beers :)

[The Prophet of Doom]

I use a morgan carbtune - imported from the UK.  http://www.carbtune.com/  Metal sticks so it is safe as can be for both bike and environment.  I've done a dozen bikes with it - it's more than paid for itself in beer :-)

Starting sync will be damn near spot on anyway as the bike was running before disassembly and carbs recently overhauled. 

The EGA is a commercial 4 Gas -  I can post readings but they won't be very interesting.  I'd love to be able to take readings at WOT, but that would be tricky - it weighs about 40kg and is mains powered.  I've heard of people doing it on the main stand with the rear brake on.  Sounds crazy dangerous to me.

[Rick G]

I use a 4 vacuum gage manifold , bought it 12 years ago . it does a fine job. I disliked the mercury tubes.

[Rikugun]

I like that Morgan Carbtune. It looks like it doesn't have the "air bubbles" flaw my Hg type does. My brother's birthday is coming up so might be a good gift idea. I'm sure he won't mind if I borrow it so it serves double duty.  ;D

[The Prophet of Doom]

A great gift idea.  It's my tool I like the most and the only one I wouldn't replace with something better if Pippa Middleton fell in love with me and gave me all her money to spend on tools.
Shipping from the UK can take ages, last parcel took 22 days for 7-10 day service.  so leave plenty of time

[Rick G]

Must have come by ship?

[dingleberry]

A great gift idea.  It's my tool I like the most and the only one I wouldn't replace with something better if Pippa Middleton fell in love with me and gave me all her money to spend on tools.
Shipping from the UK can take ages, last parcel took 22 days for 7-10 day service.  so leave plenty of time

Theres only one tool I would need if Pippa fell for me... :P

[Neil]

Wow, this debate on carb sync procedure is quite a controversy. Being just a little crazy, I'll stick my two cents into it. My experience as a dealership motorcycle mechanic in the '70s and attending Honda technical training school ("factory trained") in those days is this: the multis were synced with a four vacuum gage set (the factory tool) at idle.

I also just checked three factory manuals from my bookshelf, a Honda CB/CL 450, a Honda CL 72, and a Kawasaki KZ 400. All specify carb sync at idle, the Kawi running with vacuum gages, the older Hondas not running with throttle movement synced through feel and cable adjustment. The Brit bikes I worked on before switching to Hondas were synced like the older Honda twins - engine off, air cleaners off, fingers in the carbs to feel the throttle slides as they moved slightly up from their fully closed positions. With a carefull ear, that could also be done by listening to the slides click as they hit their stops when the throttle grip was opened and closed and adjusting for one simultaneous click.

[Rick G]

All of those had slide carbs. The vision has butterfly's and the carbs have no resemblance to the throttle valve carbs

I was there too,  started in 63 and  quit in 80.  Service manager  for Allied Suzuki in Upland CA. , Norwalk cycle (BMW and Yamaha and Mason motors  In Pasadena CA. Yamaha, Triumph  and Vespa. Went back to it in 2001 for Motorcycle specialties in Salem OR . and Dunton Motors in Kingman AZ . Arctic cat. from 2005 to 2007 In OR> I worked for  Randy Lane  , a nasty tempered old coot (older than me)  who was VERY sharp and taught me a lot. He was the one who started me syncing at 2500 rpm and he was right.

[Cdnlouie]

Hey welcome aboard Neil! Good background on the "old days" and exactly the procedure used to synchronize those old engines. The controversy here is really about "significance" of the carb synchronization.  There is a difference between synchronizing "for idle" and synchronizing "at idle." There is no doubt that you check the vacuum levels "at idle," but this is where the Vision is quite a bit different than the slide carburetors. The goal is to get the mixture screws dialed in so that you get a balanced idle setting, before you start fiddling with the throttle plates (assuming they are at least set close enough to close properly). Here is the tricky part, most of the Vision carburetors always include more turns out on the rear cylinder than the front.  On the old multi-fours with slides you never had to worry about the mixture screws except to set them all at 1.5 turns out and you were golden.  Just the same, using the vacuum gauges of the past you would not just set the synchronization without observing how the engine pulled, off the "at idle" position. That needle bounced like crazy at idle and you could only be sure you got it right by bringing it under load. Sure you do the adjustment "at idle," but you also observe the vacuum under load to see that they really are pulling together.

The Vision needs to be observed for vacuum alignment "at idle" (primarily a result of mixture settings "for idle"), then observed for behaviour when you transition to the low speed fuel circuit and finally the main jet circuit.  Any fluctuation in vacuum during these transitions may indicate where you have carburetor blockages, engine wear, or something else you can't see. I hope this sheds some light on the misperception that it is one or the other position to check synchronization, in reality it includes both.  A technician must decide the "significance" of his vacuum readings and end up making his final adjustment according to that evaluation. I believe that Rick is taking into account the bigger picture or "significance" of a carburetor synchronization (at least that is the way I understood it).

[Neil]

Thanks for the additional info, Louie.
The bouncing gage needles are not an issue with the Honda factory gage sets I have used and own. Each gage has a damper valve that can be adjusted to reduce the bouncing to very little - within 1 increment or less on the gage face. It is true that the mixture or air screws base setting was typically 1.5 turns out, but there was always a +/- part of the spec and we knew to fine tune them they should be turned in or out to find the highest idle speed. On the Vision carbs, I do know about the different starting point setting for the rear from the front. Perfect sync on the gages at idle is great, but how the motor pulls and responds to opening the throttles off idle is also important.

Maybe this controversy can be concluded with the suggestion of checking sync both at idle and at a higher RPM, see if it is different or not and adjust to individual preference.

BTW - another tidbit of factory info - my 1983 Canadian Yamaha RZ 350 has two cable operated carbs. Each carb body has a sight glass window in it and each throttle slide has a mark on it that aligns with the windows. The marks are visible in the windows when the slides are all the way up...full throttle. This is for carb syncing and the factory manual's instructions are to open the twist grip all the way and check the throttle slides' marks in those windows, and adjust the cables as needed to position the marks identically in the windows. So, this factory info is to sync at full throttle. My training was full throttle syncing is for racing and sync at idle or at a small throttle opening for street riding since that is where most riding is done.

[Cdnlouie]

Couldn't agree with you more! You have nicely described the different scenarios of carb synchronization including both purpose and design.

I also worked for a Honda dealership back in the 70's which also included the one of the oldest Brit bike dealers in Canada, those were exciting days with Honda leading the pack. Yes the vacuum flutter adjusters were a good idea for the time, but I sure enjoy the new Morgan Carbtune.  For the early 80's I moved to a Yamaha dealership and caught the wave of the next most exciting motorcycles in the era (Vision included).  However, I never owned a Vision until the start of the 21st Century (my second childhood).

 

[Rick G]

Syncing at idle is a given. syncing again  at 2500 provides  much smother performance and better throttle response. For racing it , because the throttle will be wide open much of the time , is a given.
I have spent  onsiderable time with my fingers stuck in the carb throat of a Triumph or BSA  ( bastard stalled again)  (British scrap aluminum) or as the Qubecois  say it   Motorcycle often stopped .  I would put my finger on my left hand in the left carb on a Bonniville and observe the right one . The splayed ports on the Bonnie prevented seeing both at the same time . BSA's and jap bikes you could get your thumb in one and your index finger in the other  and feel when the were lifting. My 4 gage manifold with damping valves makes it so much easier!

[Neil]

"BSA's and jap bikes you could get your thumb in one and your index finger in the other  and feel when the were lifting."
Nortons, too.