Throttle Body Sync Hose

I think I correctly completed my first Throttle Body Sync., though I have some questions that hopefully someone could answer.

1) The service manual does not state how the sync hoses are numbered. May I assume cylinder hoses were assigned, throttle body #4 [long - pink band] with #3 short (clutch side), and #1 [long - pink band] with #2 short (throttle side)?

2) I have the Morgan Carbtune Pro which is marked in centimeters of mercury pressure (cmHg). The service manual calls for the vacuum pressure "Intake vacuum 29.0 kPa (8.6 inHg) (218 mmHg)", so I converted 218 mmHg = 21.8 cmHg. Problem was I could never reach at idle, body #1 as standard, 21.8 cmHg. Could this be due to related to question 1?

Anyway, I adjusted #1 to a sweet spot by ear...

Other than that... during the initial view #2 and #3 were evenly lower than #1 and #4 by about 10 cmHg. I was able to even all at idle and oddly at 4000 RPM all remained even. Oddly because I was thinking at idle there would be differences than at speed.

Comments?

From what I remember, you did hook up the synch hoses correctly. Even if they were wrong, you'd still be able to synch, as turning a synch screw is always going to adjust only one cylinder. Hooking the hoses up in order is more for convenience.

It's also important on carbed bikes where you'd synch by adjusting the throttle shafts, and some adjustors affected more than one carb. The FZ6 has that neat box with all the screws in one spot, so we don't have to deal with that issue.

On mine and Pete's bike, we synched for about 5000 RPM or so. When we did that, the idle got a bit out of synch. If yours is at synch at idle and at speed, consider yourself quite lucky. My best guess is that somebody did a really good job of aligning the throttle butterflies on your bike. If they're all in perfect unison, you might not get the variances in vacuum at different throttle openings.

(I'm not recommending that anyone start adjusting their throttle plates. Without a flowbench, you'd probably just make things worse.)

Fred

Thanks Fred. I feel more at ease.

Fred said:

From what I remember, you did hook up the synch hoses correctly. Even if they were wrong, you'd still be able to synch, as turning a synch screw is always going to adjust only one cylinder. Hooking the hoses up in order is more for convenience.
Fred

Click to expand...

I did attached in order #1 and #2 to throttle side with #1 on the long hose with pink band. The other two were attached #3 and #4 clutch side with #4 on the long hose with pink band.

Note: The pink bands were not very clear but having a long and short hose to distinguish #1 and #4 was brilliant I thought.

Fred said:

...If yours is at synch at idle and at speed, consider yourself quite lucky. My best guess is that somebody did a really good job of aligning the throttle butterflies on your bike. If they're all in perfect unison, you might not get the variances in vacuum at different throttle openings.
Fred

Click to expand...

Interesting... I didn't put much thought to the throttle valves themselves. Yes! I do believe I have a well assembled bike because they do all stay much the same at speed.

I wish I could have set the target of 21.8 cmHg but I'm not going to concern myself too much. I didn't use the Yamaha gauges so there maybe some differences on readings. Maybe next time I will write down a reference number for my setup and post it.

Fred said:

(I'm not recommending that anyone start adjusting their throttle plates. Without a flowbench, you'd probably just make things worse.)
Fred

Click to expand...

Whoa! Your right, not a good idea. It's listed as a "Caution: Do not use the throttle valve adjusting screws to adjust the throttle body syncronization."

mglowe said:

I wish I could have set the target of 21.8 cmHg but I'm not going to concern myself too much.

Click to expand...

We didn't have a vacuum gauge either. Since we were doing the initial service, we just left the #1 cylinder well enough alone. If it was good at the factory, it's probably still good a few weeks later.

Fred

Ooops!

A late viewing of Fred and Hellgate's Throttle Body Sync Video and further discussion with the local dealer I feel it important that I should make a correction to the hose numbers. I would not use the numbering in my previous posts.

CORRECTED: Sitting on the bike looking forward, the left sync hoses are number #1 [long] and #2 [short]. The right side hoses are #3 [short] and #4 [long].

Probably making more out of this than needed but it should help one to hookup the correct numbers to the gauges. This is why I had difficulty figuring out originally what was adjusting what - if that makes sense.

What also sucked was I adjusted the #1 sync screw when I should have left it alone. I think I moved it back to where the factory set it (if at the initial 600 mile service it was not adjusted by the mechanic) but I have no way of knowing.

With the #1 sync screw back at original position, I think, and a re-sync she does run very nicely and overall I'm happy. I learned much from this and with the work replacing both my tires I appreciate my bike even more.