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81-83 650G Carb Tuning

  • Thread starter Thread starter wad650
  • Start date Start date
W

wad650

Guest
I have not got the book yet ( has been ordered should be here sometime this week) and I am not sure on how to sync the carbs. I have cleaned two of them and I have ordered the rebuild kits and I am not sure on how to re-sync the carbs once I am done. My brother has an 850 and he has a Merc tuner and I don't know if this will work with my bike. If not what do I need and where can I find it.

Thanks
Wade
 
Borrow your bro's mercury sync device and use it on your 650. Same procedure for both bikes.
 
ok so i have 80 55oL how would i sinc these i have no tools
 
Twins can be sync'ed by pulling off one plug wire but that won't work with a four. Crack open the piggy bank or make your own tool using a round vacuume gauge and some valves so you can switch from one cylinder to another.
 
I will ask him :). Thanks for the help guys that is the only thing so far I have had issues with on this bike it runs just not right so I decieded to rebuild the carbs and I hope that does the trick. The carb at the end on the right side was in really bad shape and I got it cleaned and I am just waiting on the kit know.

Thanks
Wade
 
Hey everyone,

Wades brother Eric here. Anyone in the immediate southwest Florida area is welcome to borrow them :) Would ship but don't think the mercury would travel that well. To anyone looking to sync their carbs you would be doing yourself a favor by buying this unit. I got mine from JC Whitney about 2 years ago for around 50 bucks or so.

Take care
E
 
I was only kidding!!! I have a brand new set of motion pro merc sycn's myself and they will not let you ship mercury without it being bottled up and will only go ground shipment.It is a tool that is well worth the money.Even if you only use it twice a year.Dont forget to get the carb tuning screwdriver to go with it.There kinda useless without it.
 
Sync Issues

Sync Issues

Ok, I have rebuilt the carbs and reinstalled them and I am not sure how to tune them. I read the book several times and I don't understand what it is asking me to do. I have two, I guess vac lines coming off of the outer cabs, the main fuel T and another 1/4 line that is attached to the second carb from left to right ( I think it is for the reserve on the tank). I don't understand where the VAC lines go if anywhere because they did not have any attached to them when I took them off so I bought some line and don't know where to put them. Also, I hooked the first line up from the MERC tuner and adjusted the throttle screw between the second and third carbs to get the bike to idle at 1750 rpm or close to so I could calibrate the tuner and the bike really did not make any change( I know the screw is doing something becuause when I put them all together I messed with it and seen the butterflies up and close when I turned it) the only way I can get the bike to idle up or down is to adjust the cable at the handlebars. If anybody could help me it would be great the bike is up and running but, I think it could run smoother and I am just not sure what I need to do.



Thanks
Wad
 
First things first. You should have one fuel line running from tank petcock to main fuel "T" between carbs 2 and 3. There should be smaller hose going from port on #2 carb that connects to tank petcock. In your last post, this is the line that you believe is for reserve, reserve is just lowest part of tank which is used by switching petcock level to access it. There most likely are two more rubber hose that connect between carb bodies 1 and 2 and between 3 and 4; these are vent hoses that allow the carbs to work properly. They don't connect to anything and are usually routed back and over the airbox plenum that connects air filter area to carb bells.

To synch carbs you will need a tool to measure vacuum (mercury sticks, vacuum guages, carbtune) an 8mm socket with extension, a flat bladed screwdriver to adjust synch screws. The synch tool attaches to a port in the rubber boot that connects carb to engine. Think of it as a carb manifold. Each of these boots has an allen bolt that is plugging port. Your synch tool needs adapters to screw into these ports, I think they are 5mm. These adapter connects to the mercury sticks by clear hoses.

In your case, you will attach a hose to each boot in order left to right 1 to 4, thus 4 hoses in total. Mercury sticks are nice since you don't have to calibrate the tool to use it; vacuum gauges and others need to be calibrated so they all read the same value for a particular cylinder. Unfortunately, you need to be careful with mercury sticks since it can be sucked into engine when revved too high. Likewise, mercury is known health hazard.
The actual synch should be done with a warmed up engine, normal operating temp. An auxiliary tank or a very long hose can be used with stock tank to provide gas. Plug vacuum hose from carb 2 and run tank on prime. I would get a large fan to blow air on motor from front on bike to help prevent over heating. Carefully attach carb adapters to boots, attach hoses for synch tool, and get gas flowing to bike. Start motor, adjust engine speed to around 1800 rpm, either by screw under carbs or rubber band around throttle. Don't rev motor and back off suddenly since this will cause a large vacuum spike that could cause mercury to be sucked into motor, not good. Note: speed (rpm) at which you synchronize is debatable, same with how you set speed, service manual recommend 1800, other have had good luck with higher speeds.
Hopefully, if you have made it thus far you will see on your sticks that mercury is pulled up a distance and ideally, they would be equal height. More than likely, they are not equal. I don't think the height that they are at is critical, only the relationship of how they are to one another. Ideally, the manual suggests cylinder 1 and 4 to draw slightly more vacuum than 2 and 3. I am personally happy to adjust them to be level across.
Since they aren't likely to line up, you will need to adjust the synch screws. First notice there are only 3. The throttle cable attaches to #3 carb and thus cannot be adjusted; they other carbs are adjusted to it. If you follow manual, you can adjust in manner to level them together, I can't remember proper order. Nevertheless, by loosening 8mm lock nut, you can affect synch screw between carb bodies and change relative vacuum on sticks. The trick isn't to get the levels to line up, that is fairly easy if motor is in good tune; the difficulty is tightening lock nut without changing the setting for the synch screws. It also should not take a lot of change to make a drastic difference in merc level, I would guess 1/4 turn at most if fairly close to start. There are carb tools available for this task, I have used socket with swivels and extensions.
As you get carbs closer to synch, you will notice bike sounds smoother and may gain rpms, this is normal and good. Once in synch, remove tool, replace tank lines and go for ride. If bike was badly out of synch, you may be surprised by smooth power delivery. Good luck.
 
waterman said:
First things first. You should have one fuel line running from tank petcock to main fuel "T" between carbs 2 and 3. There should be smaller hose going from port on #2 carb that connects to tank petcock. In your last post, this is the line that you believe is for reserve, reserve is just lowest part of tank which is used by switching petcock level to access it. There most likely are two more rubber hose that connect between carb bodies 1 and 2 and between 3 and 4; these are vent hoses that allow the carbs to work properly. They don't connect to anything and are usually routed back and over the airbox plenum that connects air filter area to carb bells.

To synch carbs you will need a tool to measure vacuum (mercury sticks, vacuum guages, carbtune) an 8mm socket with extension, a flat bladed screwdriver to adjust synch screws. The synch tool attaches to a port in the rubber boot that connects carb to engine. Think of it as a carb manifold. Each of these boots has an allen bolt that is plugging port. Your synch tool needs adapters to screw into these ports, I think they are 5mm. These adapter connects to the mercury sticks by clear hoses.

In your case, you will attach a hose to each boot in order left to right 1 to 4, thus 4 hoses in total. Mercury sticks are nice since you don't have to calibrate the tool to use it; vacuum gauges and others need to be calibrated so they all read the same value for a particular cylinder. Unfortunately, you need to be careful with mercury sticks since it can be sucked into engine when revved too high. Likewise, mercury is known health hazard.
The actual synch should be done with a warmed up engine, normal operating temp. An auxiliary tank or a very long hose can be used with stock tank to provide gas. Plug vacuum hose from carb 2 and run tank on prime. I would get a large fan to blow air on motor from front on bike to help prevent over heating. Carefully attach carb adapters to boots, attach hoses for synch tool, and get gas flowing to bike. Start motor, adjust engine speed to around 1800 rpm, either by screw under carbs or rubber band around throttle. Don't rev motor and back off suddenly since this will cause a large vacuum spike that could cause mercury to be sucked into motor, not good. Note: speed (rpm) at which you synchronize is debatable, same with how you set speed, service manual recommend 1800, other have had good luck with higher speeds.
Hopefully, if you have made it thus far you will see on your sticks that mercury is pulled up a distance and ideally, they would be equal height. More than likely, they are not equal. I don't think the height that they are at is critical, only the relationship of how they are to one another. Ideally, the manual suggests cylinder 1 and 4 to draw slightly more vacuum than 2 and 3. I am personally happy to adjust them to be level across.
Since they aren't likely to line up, you will need to adjust the synch screws. First notice there are only 3. The throttle cable attaches to #3 carb and thus cannot be adjusted; they other carbs are adjusted to it. If you follow manual, you can adjust in manner to level them together, I can't remember proper order. Nevertheless, by loosening 8mm lock nut, you can affect synch screw between carb bodies and change relative vacuum on sticks. The trick isn't to get the levels to line up, that is fairly easy if motor is in good tune; the difficulty is tightening lock nut without changing the setting for the synch screws. It also should not take a lot of change to make a drastic difference in merc level, I would guess 1/4 turn at most if fairly close to start. There are carb tools available for this task, I have used socket with swivels and extensions.
As you get carbs closer to synch, you will notice bike sounds smoother and may gain rpms, this is normal and good. Once in synch, remove tool, replace tank lines and go for ride. If bike was badly out of synch, you may be surprised by smooth power delivery. Good luck.
Click to expand...



Thank you very much I will be messing with it tomorrow and with the way you explained it, it should be a lot easier to follow then the book. I will let you know and thank you for the help this site is great.
 
I would follow the service manual, I typed that response from my head fairly late at night. I would also say to use search feature on this forum, the synch procedure is fairly universal between models. The confusing part in the service manuals is that they use a suzuki synch tool which isn't readily available. The suzuki tool needs to be calibrated to itself before using. Mercury stick don't require this calibration. Good luck.
 
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