Does a change to float levels require re-synching?

I adjusted my float levels on 3 carbs. Is it likely necessary to re-synch? I don't have a YICS tool or vacuum guages so, I am hoping that it is not necessary. I haven't had a chance to ride it yet, but it sounds fine. Thanks in advance.

 

If the levels were pretty close you should be OK.

 

Float levels have nothing to do with synchronization, it's the relationship of the butterfly valves and how you match them to get the same air flow through each carb. Idle mixture may also play a role in the procedure.

 

Steve if his levels were real low it would give a lean condition & would effect sync'.

 

I'm sorry Wiz, but I must disagree, while theoretically possible, really low bowl levels are practically impossible unless the float valves are clogged. The butterfly valve adjusters are what "sync" the carbs. Of course, other factors can affect the syncing of the carbs, such as intake and exhaust valves out of adjustment.
Hamster, my advice to you is first listen to the engine as you slowly give it throttle, you may be able to tell if they are out of sync. If not, see if you can borrow a YICS tool and some gages, if you are good at making things you can make a YICS tool and a manometer, there are threads that show you how to do it.

 

I agree with Steve - effect of fuel level in bowls on sync is so small as to be negligible. Certainly there is 10 fold more inaccuracy in the gauges than the fuel level effect.

What can affect them is flexing of the rack as you fight them in and out. Again, probably too small to worry about.

 

I wouldn't say negligible; an overly lean or overly rich running carb would tend to affect sync-- by throwing it off a tad. Possibly enough to noticeably affect running.

Unless somebody sync'ed it with the wacky float levels, I would think that setting them right would improve the sync.

 

Thanks for the replies. Gave me the confidence to just go out and confirm in a bottom-line kind of way. Beautiful sunny day, rides like a champ. Pulls strong from nothing to redline. Curiously, it seems to idle lower now, holding a smooth idle at something a little over 500 RPM. It had been running rich, and I have had a recurring stuck float (twice, held open by a bit of crud), so the float levels were lowered just a tad from a clear tube read that was a little high. So it all made sense until I was done and THEN wondered if I hadn't opened up a can of worms at the height of the season.

The discussion did raise a theoretical question for me. Float level affects running rich/lean. So does the mixture screw. What is the difference between the two? Is one micro and the other macro? Or the effects are at different engine speeds? Or what? Just trying to get some schoolin'.

Thanks again.

 

Idle is supposed to be 1000 +/-50 rpm. I'm really not sure idling at 500 rpm is possible, but it's not recommended. Usually idle is high enough to also ensure proper oil pressure to reach the top of the engine.

 

Fuel level affects mixture over the whole range. Mixture screw just at idle and very slight throttle opening.

If you've really got a good idle at 500 rpm you probably aren't far off. Crank the idle up to 1000.

 

If the fuel levels have no effect why is it always a precursor to synchronization ?

 

(because they do matter.)

Idle speed for the 650 is supposed to be 1050~1100rpm. DO NOT let it idle at 500 rpm; it needs at least 1050 to be making the right oil pressure. Beaucoup important, these are plain-bearing motors.

 

I was wondering if you CAN idle a 650 bike at 500 rpm, or if his tach might be malfunctioning.

It could be that his definition of a good idle is more lopey and "harley like" than what these XJs are supposed to be, i.e. "sowing machine". Don't try to sync with that idle, because the sync won't mean anything at 500 rpm.

In fact, I was getting used to my kinda lopey idle when I made some tweaks to my pilot mixtures. Finally got around to re-syncing, and now the idle SOUNDS higher, but I think it's just the lopei-ness that's missing at idle rpm.

 

It might be possible but it's torture.

Sewing Machine idle=you got it right.

NO "lope-lope-lope." Loping idle=hard on things. Like "primary" chain tensioners in the shafties.

 

Yeah, I only mentioned the low idle as a observation of what happened when I got my fuel level a little lower in the bowls. At the second light I reached down and dialed it right up to 1000 or a little over. No malfunctioning tach, this thing was definitely running so slow and it sounded smooth, just real slow. Made me think every thing was just right with it, except a really low idle. Gotta ride it way out to an overnight party tomorrow. Supposed to be gorgeous. Probably take the long way. Thanks for all the input. It's always educational around here. Ride safe.

 

Glad we could be of assistance, good luck and be careful out there.