Message to MRO

[oldyam80sg]

MRO- you told BrownBear that you would take his carbs and sync them on one of your bikes if he shipped them to you.Would you be interested in doing that for me? I would definitely pay you for your services.Just wondering.

[TopCatGr58]

Hey Yam,

As MRO said, it would get "him" started, to a starting point, but "he" would still need to vacuum synch them on "his" machine, because each engine flows differently due to ring/valve wear, timing, etc.! For the cost of shipping them to and back from MRO you can invest in a set of vacuum gauges and do it yourself!

Not poo pooing MRO's offer, he's helped another member get his carbs in working order, is very good, etc.! He'll probably chime in here saying the same thing I've just said, it's only a starting point!
T.C.

[oldyam80sg]

Thanks TopCat- I used to have a guy that did all my work but he will only will do current bikes.I never did carb syncing before, wish me luck!

[TopCatGr58]

Hey Yam,

Vac. Synch is right up your job line...."Maintenance" and you're a mechanic...no problem! And I bet if you posted a message, you'd find some Xsives in the "Jersey" area to assist you!
T.C.

[oldyam80sg]

TopCat I'am a printing press mechanic. I fix early 1900's German Heidelberg printing presses that i have personally converted from ink to foil stamping presses.I do dabble in a little bit of everything but never carb syncing.

[Pat Kelly]

Carb sync'ing isn't rocket science.
You'll need four vacuum gauges (dial or mercury, really dosen't matter. I use mercury sticks) and a source of fuel. The vacuum to your petcocks will not be available for the petcocks. A large fan blowing over the engine helps cut-down on overheating.
Hook the four gauges to the four vacuum fittings on the carb boots. Keep them in order right to left, it's just easier. Start the bike, DON'T REV IT (if you're using mercury it will be sucked out of the tool and you'll have to get more mercury).
Look at the gauges and note if they have different readings (the actual numbers don't matter, the goal is to have them all read the same when you're done).
If #1 and 2 are different then they need to be adjusted (ignore 3 & 4 at this time). There is an adjustment screw between 1 & 2 near the front (engine) side of the carbs. Turn this screw until the gauges read the same. The gauges will probably be bouncing a bit so really close counts, so they don't have to be exact. (On my bike the reading changes with the pressure of the screwdriver so they should be close when you're not touching the bike).
When 1 & 2 are good then do the same thing with #3 & 4 (ignore 1 & 2). The adjustment screw is between 3 & 4.
Now 1 & 2 should read the same and 3 & 4 should read the same (though 1-2 might be different than 3-4).
Now adjust 1-2 to 3-4. The adjustment screw for this is between 2 & 3.
You may have to go through this a few times to get them all the same. 1 & 2, then 3 & 4, then 1-2 to 3-4.
Syncing the carbs sets them to all do equal amount of work. When they're out of sync then one cylinder is doing most of the work and the others are doing (progressively) less.

On a controversal note, I sync my carbs at about 2000 RPM using my cruise control to hold the higher idle (not the idle adjustment screw). My reason for this is the sensativity of the adjustment on my. I found (on my bike) that when I GENTLY raised the RPM after syncing the readings changed as the throttle cable pulled-up on the inner carbs and the outer carbs then followed.

[mro]

but never carb syncing.

For the cost of shipping them to and back from MRO you can invest in a set of vacuum gauges and do it yourself!

If all else is well with your carbs.....
Pretty sure you will be very happy with results the first time you do it yourself. Actually the BS34 carbs are not complicated and the only special tool needed is a synchronizer (plus yicks tool for XJ).
Where newbie's seem to have a problem....
Sync screw on carb #1 only adjusts carb #1
Sync screw on carb #2 adjusts both #1 and #2 together
Sync screw on carb #4 only adjusts carb #4
No sync screw on #3

Adjust #4 to #3
Then adjust #1 to #2
Then when you do #2 to #3 (screw on #2 adjusts both #1 and #2 together)
As you adjust one carb to another, sometimes one you’ve just done may change a little and need to be re-adjusted.

As your adjusting em, RPM may change. Keep RPM the same (around 1000/1200)
Leave sync tool attached when done.
Good time to adjust pilot screws.
I adjust idle as low as it will go and engine still run relatively smoothly, then adjust pilots (matters not what order pilots adjusted) After adjusting a pilot screw check RPM and adjust as needed and then do the next one.
After pilots adjusted...re-check sync and adjust as needed.
Set idle speed with main idle screw.
Remove sync tool and test ride.


mro
btw, I sync em with the air box/filter installed and a box fan blowing on engine....

[mro]

Carb sync'ing isn't rocket science.

and a source of fuel

I just place a piece of 2X4 where tank bolt is to hold up tank and put petcocks to prime.

On a controversal note

I agree that if your throttle shaft has some "play" between carbs this might be a good idea. I've not noticed this on an XS yet...


mro

[wingnut]

I have. During sync of #1 & #2 I notice that a little downward pressure on the adjustment would change the reading. I still sync at idle but it takes a little longer. I have noticed some build up around the throttle shaft seals so they are going to be replaced. Afterward I will see it the downward pressure does the same thing.

Dave