Synchronizing - please help me

[PoPr]

Hey all, starting a new thread, cause my old ones got OT.

Im going to synch my GS750E -79 tomorrow and I need HELP. I have never done this before. My Haynes manual sucks at this specifical chapter.

First off, I have build myself a vacuum synch tool, se pic here. I am synchronizing my carbs in pair.

I have performed a bench-synch.
So WHAT should I do next??

Take the bike out for a quick run to get her warmed up.
Take off the fueltank and use a longer hose to have it beside the bike while testing.
Use a large fan to cool engine while testing.

Ok, here it comes, I have no idea how to synch them! Should I connect my two synch-hoses to the vacuum-ports pointed out in pic #1? And I dont have a vacuum-port on carb #1, its plugged up!
Then screw of the top of the carbs and adjust the synch with the screw on top of the slide pointed out on pic #2?

Or am I way off here? I am getting confused! =/ Need help fast, as I am having the bike inspected in two days!

Pic 1


Pic 2

[odl777]

you are right about pic 2 but in pick one you will go to the manifold you know were there is a allen type looking bolt right by your rubber boots that hook to your carbs. loosen that and plug you sync tube into them. Also, a bench sync i beleive is just for the ease when you sync the carbs, so no need to test ride just let warm up a bit. Good luck and if you any more questions just post.

[PoPr]

ah, I see. Thank you odl.
So I´ll hook up the synch-tool to them. Should I sync #1 and #2, cut engine, then #3 and #4, cut engine, and lastly #2 and #3?
I love this forum, am I weird?

Oh, one more thing. I don´t have the bike here at my home, so I cant look and see. How do I fit my sync hose to those "allen bolt holes"? Do I need a "nozzle" (like the end of the hose on this one) on the end of my hose, or can I just plug the hose in the hole without a nozzle?

[Jethro]

You need a fitting, ideally one that is brass and threads into where the allen bolt is. The gauge you made will do the trick, but IMHO, the price of the Motion Pro synch tool is worth it for the fittings alone. And you can do all 4 carbs at once, which, if you use a rubber nozzle in the vaccum synch port may melt, becasue it's gonna take you 4 times as long to synch the carbs- the manifolds are going to get hot.

[dcpower]

Carb Tool

Just Ordered 4 Brass Fittings From Bikebandit To Hook My Sync Gauges To They Were 13.00 Cdn Dealer Wanted 16.00cdn

[PoPr]

Thanks everyone, I'll have a go for it tomorrow.
BTW, approx how much force is 3.5ft/lb? Tighten with finger power + how much with a wrench? 1/4? 1/2?

[thr3shold]

Thanks everyone, I'll have a go for it tomorrow.
BTW, approx how much force is 3.5ft/lb? Tighten with finger power + how much with a wrench? 1/4? 1/2?

3.5 lb-ft is very minimal. A 1/4"-20 bolt only takes 9-11 lb-ft of torque to be properly torqued.

[ghwrenchit]

Hi there,

No offense, but in looking at the pic of the sync tool, I'm not sure its going to get you there. Is the line running down around the bottom loop all one continuous line ? I think you will need more of a situation like multiple straws drinking from the same cup kinda thing, but I can't tell from your picture. Just a thought, love the gauge thought, want to make one myself.

Greg

[mark]

Just having two hoses won't cut it from my experience. For VM carbs you need to see all four carbs at the same time. Adjusting one impacts the others. When you do it, you'll see.

Also make sure you have a couple of good fans running when you're doing the synch.

Make sure your valves are adjusted correctly as well before you begin. Make sure your air box is hooked up correctly of course.

The vacuum bolts for the synchronizer are on the carb boots facing down and out. You'll definitely need the brass fittings to make it work.

Do your air screw adjustment for highest rpm too.

Have a long piece of hose line hooked up so you can pull your tank off and still have plenty of gas getting to the carbs. Dont try to do it with just gas that's in the carb itself.

Make SURE that you plug your vacuum line to the petcock with something to maintain proper vacuum on carb #3.

Good luck.

[wiredgeorge]

Step one. Get rid of Haynes manual
Step two. BUY A MANOMETER WITH FOUR MERCURY TUBES
Step three. If you bought a Clymers manual, it would show you that you are trying to sync your carbs using the vent port which has no vacuum. It isn't possible to sync carbs doing them two at a time... or at least, it would be painful beyond my patience. The vacuum ports should be on your intake manifolds. Leave the vents OPEN... those are located in your pic between 1 & 2 and 3 & 4. The identical brass fitting on the #3 carb IS vacuum... basically a hole going down to the venturi of that carb and intended for connection to your vacuum actuated petcock. If it isn't used, PLUG IT with a 3/8" vacuum cap or connect it via hose to your petock's vacuum port but it MUST be capped or connected else it presents a huge vacuum leak in the carbs and you won't do ANY synchronization.

Here are some general steps... Get a longer piece of gas hose; perhaps 18" to 24" in length and connect your petcock gas out to your carb in. You can them prop up the back of your tank about 10" using a can or something under the tank so you will have room to work on the carbs using your tank as the gas supply.

Warm bike (then turn it off)
Connect manometer to vacuum fittings on intake manifolds
Loosen locknuts on all four slide adjusters
Start bike
At idle, adjust mercury/vacuum level so that all four cylinders are the same.
Stop bike and tighten locknuts while holding the screws with a flat blade
screwdriver (I take tank off before doing this step)
Replace carb tops

When reading your Clymer or Factory manual, they spec a vacuum LEVEL that should be achieved. If the vacuum is too low across all four cylinders, you did the bench sync wrong. Read the Clymer or factory manual you bought and follow the exact steps used to bench sync. You will hear lots of opinions on how it COULD be done but most will set the slide heights at an incorrect level where you can't get the idle speed where you need it.