Sync instructions are real clear...

[Guest]

“…see if the two steel balls stay equally at the lower level line, as they should, to signify that the two carburetors, “R” and “L”, are in balance: if not, remove the carburetor assembly from the engine, and loosen lock nut and turn throttle balance screw 2 to adjust the throttle valve setting in “L” carburetor." Clymer Manual

Okay, this is for a GR 650 twin, but can anyone help figure this out? I'm supposed to take the assembly off the bike to adjust the balance? Seriously?

This makes no sense to me. Would I have to install, check them and take them out again if they are still out of balance? And which direction would I turn the adjustment screw? How would I know when they are balanced?

[Steve]

Can't imagine why you would want to remove the carbs from the bike to adjust the sync.

The whole purpose is to balance the vacuum levels, which is easiest to do while running.

.

[robertbarr]

It's not uncommon to find shameless, egregious mistakes in these manuals -- including the factory manuals. Obviously, what they suggest shouldn't have made it past an eighth grade proofreader.

Examine your linkage, and you'll find an adjustment that changes the throttle setting of one carb relative to the other. It will be separate from your idle setting screw. On a twin, this should be pretty clear. Usually you can see that the tab for the sync screw is overlapping a tab on the throttle shaft of the other carb.

In other words, turning the throttle shaft via the throttle linkage doesn't directly operate both butterflies; it operates one, and turns against an adjustable tab that in turn operates the second carb. Changing that adjustment will alter the balance between the two carbs.

[JEEPRUSTY]

A lot of manual issue have to do with the inability of Japanes to tranlaaste well into the lesser language of English.

I doubt you need to remove a carb rack to do the adjustment.

Try adjusting the sych with the rack on the bike.

The manual is clearly failing in a language translation.

[oldrookie]

It's not uncommon to find shameless, egregious mistakes in these manuals -- including the factory manuals. Obviously, what they suggest shouldn't have made it past an eighth grade proofreader.

Examine your linkage, and you'll find an adjustment that changes the throttle setting of one carb relative to the other. It will be separate from your idle setting screw. On a twin, this should be pretty clear. Usually you can see that the tab for the sync screw is overlapping a tab on the throttle shaft of the other carb.

In other words, turning the throttle shaft via the throttle linkage doesn't directly operate both butterflies; it operates one, and turns against an adjustable tab that in turn operates the second carb. Changing that adjustment will alter the balance between the two carbs.

Ahhhh! That helps. Put that part back together when I cleaned and reassembled, but didn't take the time to figure out how it works.

Thanks for the replies everybody.

[oldrookie]

Well, I went back to the basics today since I was too aggressive on the first go round of cleaning the carbs. I didn't bench sync or check the float adjustment...just slapped them together and started her up.

So, went back and tore them apart. Bench sync says they were just the tiniest bit off. I think I know why the manual says to take them off the bike to sync. Simply impossible to reach the sync adjustment screw as they sit on the bike. Just can't.

Floats seemed to be adjusted correctly according to every thing I could figure out. Seems to run a little more smoothly. Time to go for a longer ride and check it out more carefully.

[oldrookie]

Runs much more smoothly at slower speed and pulls higher into the rpm range before getting vibey. Slowly making improvements.

Next up, tires. Need to replace the 11-year-old rubber.

[Topman]

I've heard you can sync your carbs at a higher RPM (say 4K or so) if you do mostly highway riding, so that you're running smoothest at that rate, haven't any experience with it though..

[Cyrillink]

I am having a lot of problems syncing up the carbs as well, I have done a full rebuild of my carb. changed all the parts, did a stage 3 jetkit upgraded and nothing.
I HAVE BEEN FUSSING WITH IT FOR THE PAST 2 weeks! i dont know what to do!
I did 2.5 turn of ideal screw does not start, did 3 nothing
2 nothing. I AM SO LOST not even funny PLEASE HELP!

[Steve]

I've heard you can sync your carbs at a higher RPM (say 4K or so) if you do mostly highway riding, so that you're running smoothest at that rate, haven't any experience with it though..

You can set your sync at any speed you want, but be aware that when you are at half-throttle, one carb might be open 49%, the other at 51% and you will never know it.

However, at IDLE, one carb would be at 2%, the other would not be open. That makes for a VERY uneven idle and a bit of surprise as you open the throttle to take off, when the other carb suddenly comes "on-line".

The Suzuki manual suggests doing the sync at 1500-2000 rpm, but I have done countless sync jobs before reading that, and I did them all at or just above idle speed: 1200-1400 rpm.

I am having a lot of problems syncing up the carbs as well, I have done a full rebuild of my carb. changed all the parts, did a stage 3 jetkit upgraded and nothing.
I HAVE BEEN FUSSING WITH IT FOR THE PAST 2 weeks! i dont know what to do!
I did 2.5 turn of ideal screw does not start, did 3 nothing
2 nothing. I AM SO LOST not even funny PLEASE HELP!

This is going to get lost, tagging on to someone else's thread, so I would suggest starting your own thread for maximum exposure.

In the meantime, what bike do you have and where are you? Someone might be close enough to help.

.

[oldrookie]

I am having a lot of problems syncing up the carbs as well, I have done a full rebuild of my carb. changed all the parts, did a stage 3 jetkit upgraded and nothing.
I HAVE BEEN FUSSING WITH IT FOR THE PAST 2 weeks! i dont know what to do!
I did 2.5 turn of ideal screw does not start, did 3 nothing
2 nothing. I AM SO LOST not even funny PLEASE HELP!

Sounds like you are confused about the carb sync process and what it does. Can't sync them until the bike runs. At that point the sync makes sure that the butterflies open at the same exact rate for both cylinders, but it doesn't really help with a "won't start" issue.

Good luck with your bike. Two weeks of fighting the same problem can be discouraging.

[oldrookie]

Uh-ho. Went out to ride this a.m. and it took a long time to start. Noticed a bit of gas bubbling up around the left spark plug.

All I did yesterday was check the float levels and adjust the sync. Finally got it started and noticed a little bit of popping on decel from the left cylinder.

Any ideas, carb gurus?

[Steve]

Not exactly a "carb guru", but I'll venture a guess.

If you see gas anywhere on the outside of our engine ("Noticed a bit of gas bubbling up around the left spark plug."),
you need to address that leak before trying to get the engine to run.

I don't understand how gas gets to be "bubbling" around the spark plug, either.

You checked the float height. Did you check it in the correct location on the float?

When is the last time the valve clearances were checked? I'll bet the GR is every bit as sensitive to tight valves as the GS.

.

[oldrookie]

Good thoughts, Steve.

Just checked the valves late last week. One out of tolerance and fixed. The GR has a system to push air into cylinders to help it run lean as a fuel conservation method.

Possible I left it on Prime last night after putting the carbs back on last night.

Got it running after I saw the gas this a.m. and it hasn't shown any signs of further trouble after sitting for the last 4 hours.

[pete]

Hopefully you've dodged a bullet there... I believe the trick is not to leave it on prime

My 450 tap doesn't have a prime position...