These carb sync instructions were provided by an ISRA member named Daddo. They were copied from a message post (#52189.5) on the ISRA Forum (http://forums.delphiforums.com) and are provided for informational use only.

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You will need to obtain a carb sync tool at any of the larger motorycle supply houses.

V-Star 1100 Carburetor Synchronization process

In order to properly synchronize the carburetors on your engine, the valves really needs to be set to their correct tolerances. And the engine idle speed should be set to it's correct range. I keep mine right in the middle of the 950 to 1050 rpm suggested by Yamaha.

The manual suggests that the bike be placed on a suitable stand or lift. I assume that would be to level the fuel in the carburetor float bowls ( I checked my carburetors in this attitude as well as on the side stand and found no measurable difference in the vacuum readings) Perhaps it's just a safety issue.

Ok, You will need to remove the Seats and Fuel Tank in this order:

• Passenger Seat - Single Allen head bolt.
• Seat Bracket (not necessary on Classic)
• Riders Seat Single - Allen head bolt on a Classic, the Custom's seat was held on by the seat bracket
• Fuel Hose - Turn fuel selector to "off", compress the fuel hose clamp and pull the fuel line from the fitting. Keep a wipe rag under the line as some fuel will run out.
• Igniter plate ( Spelled Ignitor in the manual) This assembly, with a rectangular electronic module on it is held on by three (3) quick fasteners. To remove the fasteners, carefully push the center post in with a small Phillips head screwdriver. Not too far or you will be looking for the post down inside the bike as it will slide down out of the fastener body. There is no need to remove it from the bike, but it must be loose to access the Speedometer lead connector. (to reinstall the fasteners, you must push the post back up through the body of the fastener until it extends far enough up from the fastener top to allow the body to compress. Insert the fastener into the hole and depress the post to where it is flush with the fastener body.
• Mud Guard - The Igniter Plate was mounted to it on the Custom
• Speedometer lead connector - You will find the connector under the Igniter plate.
• Remove the Fuel Tank. - Two bolts, on both the Custom and the Classic.
• Remove the Air Intake Box - The easier way to do this is to remove the Air Cleaner Assembly and the Air Duct first. The Air Intake Box is held in place by a hose clamp on each Carburetor, another on the top end of the Air Duct, and another on the breather hose that comes out of the front cylinder head.
• Remove the two vacuum plugs. Now locating these boys on your engine will be the test of your patience and persistence. The carburetor vacuum ports are on the ducts which leads from each carburetor into the cylinder head. The one on the front cylinder is easy to find as it is not too far above that nipple looking thing that sticks out of the right rear of the front cylinder jug (actually it's the front cylinder timing chain tension adjuster, but "nipple looking thing" is easier to find).

The second vacuum access plug is not actually at the carburetor duct, but is actually on the line that runs from the rear vacuum port to the A.I.S. that hides in the storage compartment of your bike. Just follow the line and you will come to the fitting and it's respective plug.

Measurement Process

1. ) Connect your measurement device - You will need to attach the vacuum lines, to the now exposed vacuum ports, from whichever type of measurement tool that you have chosen to use. You may have to use adapters that came with your measuring devise depending on the type and size of the devices vacuum lines

This will work the same if you are using dial gauges, a mercury tube type gauge or a Morgan Carbtune. Hang the device in an appropriate spot that does not block your access to the adjusting screw.

The accuracy of your measurement is really dependant upon how well you follow the device manufacturers directions in damping the engine pulse on the vacuum lines going to the testing device that you are using. All directions will differ slightly but the goal here is to restrict the flow of air in the test lines to the point where the relative vacuum can stabilize, but the flow is so restricted that it will negate the violent pulsing of the indicator. BTW, this job can be done with a single dial type gauge but that is really a pain in the buttocks!

2. ) Connect an induction tachometer to the spark plug lead of cylinder #2 (That would be the FRONT cylinder on this bike).

3. ) Start the engine and let it warm up for a few minutes.

Now this is an issue for you to consider, and a choice for you to make. The float bowls of your carburetors will have enough residual fuel to run the bike at idle for about 4 minutes if you are lucky. This is more then sufficient time to sync the two carbs, but the engine must be HOT to get accurate readings.

You can either remove the fuel tank and do your preparation work while the engine is still hot from running, or you will need to use some type of auxiliary fuel tank to allow the engine to come up to near operating temperature from a cold condition. A lot of motorcycle supply houses sell small plastic remote fuel tanks that hold a liter or so of gas, or you can salvage a tank from a discarded lawn mower and use that as I did.

4. ) Synchronize carburetor #1 (rear) to carburetor #2 (front), by turning the synchronizing screw until both vacuum gages read the same. That screw can be found between the V and just under the carburetors. On the left side of your engine, you will find a chrome carburetor cover. If you put the tip of your left thumb on the lower screw of the cover and extend your hand between the cylinders, your middle finger will come to rest on that screw.

The difference between the two gauges should not be more then: 1.33kPa (10 mmHg).

And the reading at idle should approximate: 34.7 - 37.3 kPa (260 - 280mmHg)

5.) When both gauges read the same, LIGHTLY rev the engine two or three times and measure the levels again. (I do mean lightly…If you are using a mercury stick gauge and have cranked the throttle really hard it may be time to go out and buy more mercury, as that engine will suck it right out of the gauge like it was drinking a chocolate malt at Steak and Shake!)

Button it up! It's a done deal! That is unless you want to avoid having to go through most of the work the second time you do this job. If so, keep reading.

Since one intake manifold already has a hose connected to it that runs back to the AIS, if you simply run an another hose from the other carburetor duct back to the A.I.S. unit, you can tap the vacuum lines right in the storage compartment. You will need to stop at your local auto supply store and pick up enough same sized vacuum hose to do the job. You will also need a vacuum line "T" as well as a couple of vacuum line plugs. Less work for mother the next time you do this job. Nothing has to come apart any more.

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