2 bottle sync tool

Getting ready to do this sync with my carbs on a 82 XJ750 seca. Could use a little help. I have the bottles and tubes made OK and I see the the small rubber boots for the vacuum line on top of each intake boot but where is the adjustment screw for each carb. I see a screw on the bottom/side of each carb is this the adjustment screw?

 

look between the carbs on the throttle rail. Should see 3 screws - one between each carb

 

to clarify a bit further; the screws that are used to adjust the vacuum sync are the screws that mechanically adjust the throttle positions of each carb relative to each other. #1, #2 and #4 have screws, #3 is the "master," it has no adjuster other than the overall idle knob.

As Bill said, those are located on the linkage in between the carbs.

 

Ha found it, Thanks guys appreciate it. I really had to jack up the tank to get in there to see them.

 

You will probably have to pull the tank to get clearance to adjust them. At least I always do - much easier.

 

OK all done. Many thanks for all that helped. And greggvickrey for the original post where I found the instructions for the 2 bottle sync. Carb 1-2 were out of sync quite a bit. 3-4 were not to bad. Bike runs nice and smooth now at slow speed.

New windshield coming from clearview shortly, once I change the head/neck bearings we will put it all together and take some pics.

 

To add to this with a question...Im setting up to do the same "bottle" sync on my xj750 Maxim to hold me over til I can get a mercury tuner from a friend...question is: After the sync with the screws on the throttle rail, then should the pilot air screws on top be adjusted? And what do you look for with those? Will it be the same fluctuation in the bottles as woth the other screws?
Okay, thats three questions...but can anyone clarify on this?

 

adjusted ? more like tweaked, the sync won't change the mixture much, if at all. but the mix might change the sync a little

this is where most guys use those colortune things. there is a thing called "the lean drop method" .
basically start rich and turn the screw in until you detect a drop in rpm, then turn out 1/4 turn. having four cylinders really makes this a art rather than science.
another way is set them for peak rpm, then 1/4 turn richer.
yet another way is set them all at 2.75 turns out and go ride

 

I lift up the rear of the tank and put a short 2x4 as a support. I can then access the vacuum ports, and use a short handled screw driver to adjust the screws. My home made 4 tube manometer has a "t" connector on one tube so I can still connect the petcock vacuum hose while synching.

I find even minor changes in idle mixture screws can throw synch off enough to be noticeable. So to get the proper mixture/synch it is a round robin of adjusting mixture, resynching, ride for a few days, check plug color/colortune, readjust mix by about a "dimes" width, resynch....then finally got it all dialed in. A 4 tube manometer really makes this process easy.

 

sync then adjust mixture screws then sync again adjust the mixture screws .... depending on your mind set you can keep doing this until you go crazy.
if after mix screws are set if there is no adjustment to be made on the sync then your done.
with out a color tune or gas analyzer you just have to decide when enough has been done.

 

Thanks for the replies...I was just informed by a friend to do a 4 tube instead of 2 to get it all aligned...IM only using the bottles to get it as close as I can until I can get the mercury tuner in hand... Thanks everybody! ...will keep an update if I hit any bumps...there usually are..

Ps. Cgutz...so youre running a 4 tube with an additional going to the petcock? Does it matter between which bottles/cylinders?

 

Not using bottles on the homemade manometer, much simpler.
I used 40 ft of tubing (10ft each column) to ensure I could avoid sucking ATF fluid into a carb. Use rubber vacuum hose for last foot to attach to bike or tube will melt and collapse. I placed a "T" in one of the lines to attach the petcock vacuum line to.

Total height of board is 5 feet to give you an idea of the size. I just lean it on the handlbars in use and you can see it from both sides of the bike while adjusting synch screws. A very slight movement will change the relative heights about 2-3 inches, so it is real sensitive. I adjust until all the columns are equal height.

 

you can get the mercury one if you want but it's no more accurate than a water one. actually since water is lighter it 's more sensitive. try it yourself, you'll see

 

Thanks for the pic cgutz, I think Im liking that set up better...so are each 4 lines direct to the carbs from the board? ...and does it matter which line ties to the petcock vac? Im thinking Im gonna adjust to your design...

Also, whats the easiest way to get the liquid into the lines?

 

you can use a syringe to fill or just suck on one end with other in fluid

 

Noted...and what about the t to the petcock? Do you have a good pic of the top end of your set-up?
Thanks

 

Thats what I did. It doesn't take much fluid, I squirted a large syringe full then had to get half of it out. Getting the bubbles out from that was tricky.

It doesn't really matter which cylinder the petcock is hooked to, according to an expert on this site.

I should have added I put restrictors in each tube. I just inserted a smaller male to male vacuum connector slide inside each tube. Don't know if it slows anything down, but it would slow down fluid going past!

 

You don't necessarily need to tie in your petcock. You can run it on prime, just be sure to switch it back to on when your done.

 

I don't even have a tank on mine when I sync/tune, made an aux fuel tank out of an old stainless water bottle and hang it on the handlebars.

 

Remembering to turn it off prime is the trick for me

 

Good point! I have to have it half choked to keep it idling right now...once I sync there can I turn the choke off and adjust from there?

 

Cgutz, if I use the petcock does that keep from having to use the primer? ...and are you using atf because its lighter or because of the color?

 

Dont see my last reply...I Will have to have it half choked cor it to idle right now, so...can I adjust there and then adjust the idle after?
...and cgutz, will using the petcock keep ot from needing it to be on prime? ...and are you using atf because its lighter, because of the color, or both?

 

Used ATF for color. Hooking vacuum to petcock will keep it running as that is the standard setup for 'run.'

Nor sure about synching when it needs choke to run. A more qualified member will have to weigh in on the causes of that. Mine was running much better than that before I synched.

 

Got it set up and air bubbles removed...gonna give it a shot in the morning, thanks for the design cguts! Will let ya know how it goes....
...any last min tips, btw?

 

last minute tip #1
keep a eye on it when you first hit the starter, depending on your bench sync it can suck the fluid right into the engine real quick.
#2
when the lines come off the carbs make sure they slope down, then up to the board. if some fluid gets overtop the board it stops at the bottom if you get it shut down fast enough

 

Polock...noted, and noted... Bench Should be close to right, things were running okay before I rejetted, despite the idle issue...will be keeping a careful eye out and a finger on the kill switch...and keep ya posted how it goes...

Thanks!

 

If you run the vinyl tube right to the port, watch as it will collapse as it gets warm and give erratic readings. I used a foot of rubber vacuum hose to connect vinyl tube to carb so as to avoid this.