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To Sync or not to Sync....

chuckycheese

chuckycheese

Forum Sage
Past Site Supporter
Charter Member
I've recently rebuilt my carbs and my bike runs just great. I notice that the idle is slightly rough.....and I mean ever so slight. You have to listen hard to hear it. Acceleration is awesome throughout the RPM range and it starts before you can hardly hear the starter. Would I gain anything by paying someone $50 or $60 to sync the carbs? I feel sure that's why the idle isn't perfect but I wonder if it could be much better. As always, thanks for the advice. :!:
 
The question is: Are -you- happy and comfortable with the engine as it is? I would never run one without syncing the carbs. I am a bit anal about even load on the crankshaft. I doubt it would make much difference after looking at how the bottom ends on these things are built though. GS engines have one HEAVY bastard of bottom end.


Tim
 
If it holds a fairly steady idle in the 800-1000 rpm range then I would personally not pay the $$$. But, if you want to sync the carbs spend the $$$ on your own setup and do it yourself. Initial cost is about what you'd pay someone else but then you would have another cool tool.
 
Me again

Me again

I thought about buying the sync tool but I guess my real question is this: Are the carbs already in sync, based on the way the bike runs??? Thanks, guys! :roll:
 
Re: Me again

Re: Me again

chuckycheese said:
I thought about buying the sync tool but I guess my real question is this: Are the carbs already in sync, based on the way the bike runs??? Thanks, guys! :roll:
Click to expand...

no they are not in sync you need to sync them and it is worth having the mercury sticks
i have them and do my carbs quiet regularly and it makes a noticeable difference
Spyder Out
 
might be a stupid question, but, have you tried the idle screw on the back of the carbs to try and smoothe it out a bit? I know on my '80 GS750E there's a knob on the back of the carbs that faces toward the back of the bike, and slightly down, an adjustment you can do by hand. I asked the same question about synchronizing my carbs a few weeks ago, and got pretty much the same response you did. Some say yes, others no, I guess it depends on whether you need to know that it's been done, or if you're like me...if it's working, don't @#$ with it!! Well, thats it for my 2 cents, Hope it helps. Dominick.......
 
Sync the carbs. If for anything, its the best preventative maintenance you could do, other than changing the oil.
 
Thanks to all

Thanks to all

Thanks for all the good tips guys. The idle is good but I still notice a slight stumble so think I'll bit the bullet and get some sticks. I appreciate all your thoughts!! :lol:
 
I own a set of carb balancers and they are an essential tool to own, so it is worth buying them. However, if you are very happy with how the bike runs, why tinker ? Also, I have a slightly lumpy idle and its not carb sync. Its a misfire. If you use a strobe light with an inductive pickup you can place the pickup over each HT lead in turn and watch the XEON tube fire. On mine, if I watch very carefully I can see the misfire on #2, there is a definate very short gap in the flicker, and at the same time the rev counter "blips". I could change the plug but I will just wait until I service it next. Also, remember that if you balance the carbs for best idle, you will adjust the balance for full throttle. Not much admitedly, but I am trying to point out that the carbs are not a perfect set-up. Jets wear and needles wear. Air intake can be colder or hotter, the air filter can breath easier in some parts than on others as it collects particles, the engine can run hotter or colder, fuel on one fill up can be of better quality than the next. There are many so many variables you can't balance them all, all the time. It sounds like your bike is in a very good state of tune. If it goes into gear (including neutral) sweetly and you can't hear the crank rattling and your idle is virtually smooth then I wouldn't adjust anything.

Would be interested to know, however, if you do balance the carbs and if you think you have gained anything.

Good luck
 
Carb Sticks.

Carb Sticks.

Myself I would try ther idle adjustment first. Most of these bikes are set up to idel between 850 to 1200 rpm. Each size may be a little different but are basicly the same. Check you manual. I'm constantly adjusting mine due to temp changes and such just to keep it right. I would also invest in the carb sticks. Everytime I do anything to the carbs I recheck with the sticks. Beleive it or not my bike runs better on old plugs then on new ones. I have 4 sets of plugs and change them about once a month. Take them out, cleam them and then put them in the back of the box. Pull out the newest old set and put them in. Also check your plug gap. An old mechanic once told me that if your doing mostly city type driving them gap at the smaller recommended number and if mostly highway driving gap at the recommended higher number. One other thing. Pull each plug and see how dirty the chamber is. Carbon build up will cause a little bit of a blip during idleing. If they look really dirty use a Fuel Injection type cleaner in the gas to help clean them up. DO NOT USE CARB CLEANER in the tank. Plays hell with the rubber O rings.
 
Re: Thanks to all

Re: Thanks to all

chuckycheese said:
Thanks for all the good tips guys. The idle is good but I still notice a slight stumble so think I'll bit the bullet and get some sticks. I appreciate all your thoughts!! :lol:
Click to expand...

If you're talking about a slight stumble when you first crack the throttle, then you're describing a characteristic of stock CV carbs. Trying to totally eliminate this will probably be futile, unless you change carbs. IMO
 
Carbs.

Carbs.

I have a set from an 84 750 that I'm going to clean and rebuild and then change over to. Then I'm going to take the stock ones and rebuild, clean, paint, polish and make pretty. They are the same size (BS32SS) and the jetting is the same. I'll let you know if I still have the same little rumble.
 
Good Stuff

Good Stuff

GREAT ANSWERS AND ADVICE!!! The bike was running very, very rich before I pulled and cleaned the carbs so the gas treatment is definitely worth a try. Also, I think I'll invest in the sticks and check it out. After all this good advice, I'm really curious to see what's really going on. Thanks to all. :lol:
 
I see this post was from almost a year ago, I was curious as to if the advice given helped?? I rebuilt the carbs this winter and I have an extremely rich condition on my 1980 GS750E and am waiting for a carb synchronizer to arrive to synch, did the gas treatment help to remove the carbon?, how many tanks did you run it through? How many turns out on the air screw did you have?? :roll: :roll: 8O :D :twisted: :twisted:

Scott
 
I got my 81 450 running lasy week. I guess I need to check my carb balance too. I have no idea where to buy the stics, is there a site to buy merc stics online
 
About the best price I have found is from J C Whitney.

Earl


kyle said:
I got my 81 450 running lasy week. I guess I need to check my carb balance too. I have no idea where to buy the stics, is there a site to buy merc stics online
Click to expand...
 
From what I've heard, you can build your own manometer...

Parts include a yardstick, 12ft of plastic tubing (the kind used for aquarium air pumps), super glue, and some ATF or similar oil...

The idea is that you super-glue the tube to each side of the yardstick, fill it with ATF to a point where it won't get sucked out, but there will be enough in there to indicate (ATF works nice because it's blood-red & easy to see). Make sure that you have an equal length of tube on each side, so the pressure will be equal...

Since a manometer is just a u-shaped tube with a heavy liquid inside, the concept remains the same: vacuum sucks the liquid up, and if it's equal, each side will rise the same amount, otherwise there will be an imbalance...
 
kyle said:
I got my 81 450 running lasy week. I guess I need to check my carb balance too. I have no idea where to buy the stics, is there a site to buy merc stics online
Click to expand...

Try a local independant shop near you. If they dont have them JC Whitney does. I got mine from a neighbor who used to have an old Yammie and a Kawa Concourse. He went back to Harley and doesnt need the sticks any more. With 3 bikes with multiple carbs I find them invaluable.
 
JC Whitney has them at jcw.com.
You would need the deluxe model that comes with the adapters to screw into the carbs.
 
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