Carburetors badly out of sync?

[jdub6092]

Took my bike in to a local shop that works on older bikes for a Wednesday appointment and was quoted 2 hours labor.
This was for a carb sync and tune, wheel balancing and road worthiness inspection.
Stopped by Friday around closing and asked about progress. Saw it on a stand and was told it was way out of sync even though I did a very tight bench sync previously and it was running pretty good up to 4000 rpm.
Supposed to be buttoned up and ready on Saturday, but no call.

Is it really possible for the sync to be so bad when it's not easily noticeable on the road?

 

[Big T]

Even if the sync is way off, it only takes a few minutes of adjusting to correct.
It takes longer to remove the tank, hook up everything than it takes to do a sync

Sounds like you need a new mechanic. I nominate you

 

[Burque73]

These bikes are pretty resilient. It's amazing how badly they can be treated, poorly tuned and neglected but still run. Maybe not run fine, or for long though. A lean condition, for instance, may not be apparent until the headers turn different colors. Spark plugs tell the story before that happens (if we bother to look at them.)

Valve clearance will affect the carb sync, bench sync is just a starting point.

 

[jdub6092]

Even if the sync is way off, it only takes a few minutes of adjusting to correct.
It takes longer to remove the tank, hook up everything than it takes to do a sync

Sounds like you need a new mechanic. I nominate you

I don't think he was saying it took that long, but for a Wednesday appointment for 2 hours of work dragging out until next week is disappointing. They had at.least 50 bikes in there, so maybe they just put me in the que and didn't communicate it. Then weren't able to "button it up" on Saturday.

The only reason I didn't do it myself is because I didn't want to buy another set of single use tools (sync gauges/color tune) and was already going to bring it in for dynamic wheel balancing and a second set of eyes to verify road safe condition.

 

[jdub6092]

These bikes are pretty resilient. It's amazing how badly they can be treated, poorly tuned and neglected but still run. Maybe not run fine, or for long though. A lean condition, for instance, may not be apparent until the headers turn different colors. Spark plugs tell the story before that happens (if we bother to look at them.)

Valve clearance will affect the carb sync, bench sync is just a starting point.

Understood that there are several factors that affect sync, and it's been 30 years since I last rode, but it seemed to be smooth and responsive. I guess I should be able to see a noticeable difference when they complete the 2 hour task.

 

[Cipher]

I don't think he was saying it took that long, but for a Wednesday appointment for 2 hours of work dragging out until next week is disappointing. They had at.least 50 bikes in there, so maybe they just put me in the que and didn't communicate it. Then weren't able to "button it up" on Saturday.

The only reason I didn't do it myself is because I didn't want to buy another set of single use tools (sync gauges/color tune) and was already going to bring it in for dynamic wheel balancing and a second set of eyes to verify road safe condition.

single use? isn't checking synch. on the rota for maintenance?
if hes juggling a lot of bikes the accumulation of even small overruns adds up quick.
sadly guys take on more work than they can handle for fear of losing out when the best practice is to appropriately schedule intake.
tire dealers do it to lessen the impact of seasonal surges in business as should anyone else similarly impacted

 

[KiwiAlfa156]

Understood that there are several factors that affect sync, and it's been 30 years since I last rode, but it seemed to be smooth and responsive. I guess I should be able to see a noticeable difference when they complete the 2 hour task.

May be. Carb sync is most noticeable at idle/just above idle. As you open the throttle the imbalance between carbs becomes an exponentially smaller fraction of total air volume passing through the carb rack.

 

[Baatfam]

jdub6092 One of the first things new people often hear when joining this forum is to do your own maintenance.

There is a good reason for that. Most shops won't know what to do with an old Suzuki, and if they do, the cost will be high.
I would say almost everyone on this forum has bought the tools and taken the time to handle the basics.
Valve check/adjust. Carb clean and balance. Oil/filter changes. It's all here on this forum.
None of this is rocket science, and if you get stuck, put up a question.

Hopefully these guys know what they are doing and you get a good running bike back soon.

 

[chuck hahn]

Ive done away with balancing and weights eons ago. Say you get weights on and some jackhole pulls in on you and you skid a tire..guess what..its not balanced anymore!!! Tear weight off and put dynabeads in. 1 ounce in front and 2 in the rear. constant dynamic balancing for the life of the tire. And i do a vacuum sync everytime i do valve adjustments so my stuff isnt one use.

 

[jdub6092]

single use? isn't checking synch. on the rota for maintenance?
if hes juggling a lot of bikes the accumulation of even small overruns adds up quick.
sadly guys take on more work than they can handle for fear of losing out when the best practice is to appropriately schedule intake.
tire dealers do it to lessen the impact of seasonal surges in business as should anyone else similarly impacted

I think the normal schedule is every year or so many miles, but since I expect to be more or less a weekend rider, I'd probably have it on a two year schedule unless running conditions dictate. I'm ok with taking it to a shop that works on older bikes while they still exist, but understand I'll eventually need to be the mechanic if I'm going to keep riding a classic.
Now that I've rebuilt a single bike, Ive got a bug to keep going. If that happens, I'll definitely expand my tool inventory.

 

[jdub6092]

May be. Carb sync is most noticeable at idle/just above idle. As you open the throttle the imbalance between carbs becomes an exponentially smaller fraction of total air volume passing through the carb rack.

It idled pretty darn good. Steady as a rock after removing choke and no hesitation taking off in 1st. I don't expect much change there. I expect most of the improvement will come from adjusting the fuel mixture.

 

[rphillips]

Mainly for Chuck, when adjusting the valves, probably appx. 5000 mi. do you find your carbs out of sync? Talking mainly CV's, but mine would need no or very little adj. after waaay more than 5000 mi. Mine just rarely needed adjusting.

 

[KiwiAlfa156]

It idled pretty darn good. Steady as a rock after removing choke and no hesitation taking off in 1st. I don't expect much change there. I expect most of the improvement will come from adjusting the fuel mixture.

IMHO a lot of folk underestimate the value of correctly adjusted mixture screws, thinking of it as 'idle mixture'. Correct pilot mixture makes all the difference in response and control when you just begin to roll on the throttle mid-corner (which you might be doing at 80 mph...)

The quickest and easiest way I found to test whether your mixture screws are within the ballpark, is to 'flick' the throttle open just a fraction so it picks up may be 2000 rpm from idle, and let it snap shut under its return spring. On a fully warmed engine the revs should pick up and instantaneously drop back to idle without the revs hanging and/or dropping back slowly, or dropping quickly and undershooting before coming back to idle, or worse stalling. Hanging idle = lean. Undershoot or stall = rich.

 

[chuck hahn]

No i dont find them out of sync usually. But the tanks off and why not just check is my motto.

 

[jdub6092]

jdub6092 One of the first things new people often hear when joining this forum is to do your own maintenance.

There is a good reason for that. Most shops won't know what to do with an old Suzuki, and if they do, the cost will be high.
I would say almost everyone on this forum has bought the tools and taken the time to handle the basics.
Valve check/adjust. Carb clean and balance. Oil/filter changes. It's all here on this forum.
None of this is rocket science, and if you get stuck, put up a question.

Hopefully these guys know what they are doing and you get a good running bike back soon.

Understood that I will need to be my own mechanic and to a pretty large extent, I have been and had my bike running well with great tips and assistance from this forum. The only things I've outsourced until now were head and cylinder work by a machinist, frame powder coating and bead blasting the carbs. Painting fairings and fender still to come.
I just happen to have a shop a couple of blocks down the road that is one of the few that works on these bikes with a top notch rating and decided to let them put the finishing touches on it.

 

[jdub6092]

Ive done away with balancing and weights eons ago. Say you get weights on and some jackhole pulls in on you and you skid a tire..guess what..its not balanced anymore!!! Tear weight off and put dynabeads in. 1 ounce in front and 2 in the rear. constant dynamic balancing for the life of the tire. And i do a vacuum sync everytime i do valve adjustments so my stuff isnt one use.

This is something I hadn't come across before, nor even thought there was a different way. I'll look this up. Thanks!

I have a static balancer and used some weights that probably won't stay on too long. If there's one thing I don't enjoy about rebuilding is spending hours trying to find the right parts that fit so just added that to my service list.

 

[rphillips]

I agree with him ^^^^ on the balancing beads. I'm not riding near as aggressive as in the past, but for my riding the beads work great.

 

[chuck hahn]

And beads can be used with tubes too. i know someones gonna ask.