Freebird

Plugging the AIS System The AIS is an emissions system which introduces oxygen-bearing air into the exhaust ports on the exhaust stroke. This induces further combustion of hydrocarbons in the exhaust pipe and greatly reduces emissions. It is driven by intake vacuum pulses. The only purpose of this system is to help satisfy our good old EPA requirements. Though good in theory, it's bad in that under certain conditions it can cause a HUGE backfire on deceleration that actually sounds like a shotgun going off. The first time this happened to me, I thought we were being shot at and my wife almost jumped off the bike. Disabling the AIS is a simple process and one that will not affect the performance of your bike in any way. The following is one way of doing so. There are two assemblies that you have to deal with. One on the rear and one on the front. We'll start with the rear and it is very easy. On the right side of the bike, just below the rear shock, you will find the first one. You'll want to disconnect the large hose with the gold clamp. Now..you can use most anything to plug the hose. I used rubber stoppers that I had picked up at a local Home Depot store. You can find these in the hardware department but a wooden dowel rod or most anything of the proper size will work fine. Look carefully and you can see that I have stuck the rubber stopper into the inlet on the AIS valve. Now in this next picture, I've simply stuck a piece of duct tape over the end of the valve and stopper. You can probably skip this step if you want but being born and raised in Texas...it's just part of my upbringing. Any job worth doing is worth using a bit of duct tape on. Besides...it keeps the plug where I want it and not up in the hose somewhere. Now you put the hose back on and you are done with the rear. That wasn't so bad was it? Don't worry...though essentially the same process, the front will give you plenty of grief simply because it's harder to get to. Now the front AIS valve is located just in front of the oil filter. The attached blurry picture is a bit hard to see but you can see the gold clamp that secures the hose you'll need to remove. Now....there are two ways to do this to make it a bit easier. The first way would be to do it when you do an oil change. With the filter removed, you can pretty much forget the rest of this write-up. Simply disconnect the hose as you did on the rear, insert the rubber plug, add the duct tape, reconnect the hose and you are done. If you are ready to do this and you are not ready for an oil change, here is a tip that will make it easier. Just below the drivers floorboard on the left side of the bike (shifter side), you will see two allen bolts. These are the bolts that secure the AIS assembly in place. Remove those two bolts and the assembly will be free, held only by the hose that you will disconnect. You can now pull down on the assembly enough to get to the clamp without skinning your knuckles. Once the hose is off, the assembly just drops out. Now...just plug this hole in the assembly as you did on the rear. Put it all back together and you are done. Not a difficult job at all. Figure about 30 to 45 minutes total.

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Synchronizing The Carburetors WARNING! Please be aware that the Yamaha Service Manual has the procedure for syncing the carburetors WRONG. The manual indicates that screw 1 is used to sync carb 1 to carb 2 and that screw 3 is used to sync carb 3 to carb 2. That is opposite of what it should be. The following is the correct procedure. NOTE: Prior to synchronizing the carburetors, the valve clearance and the engine idling speed should be properly adjusted and the ignition timing should be checked. 1. Stand the motorcycle on a level surface. NOTE: Place the motorcycle on a suitable stand. 2. Remove vacuum plugs. 3. Install: Adapters Vacuum gauge (Fig.2) Engine tachometer (Fig.2) to the spark plug lead of cyl. #1. Vacuum gauge: YU-08030-A, 90890-03094 (These are Yamaha part numbers. Any suitable mercury sticks, or other suitable gauges are just fine) Engine tachometer: YU-08036-A, 90890-03113 (Yamaha part numbers. Any suitable tachometer will work. A tachometer is not absolutely required 4. Start the engine and let it warm up for several minutes. 5. Check engine idling speed. If out of specification, adjust to 950 to 1050 RPM. Refer to "ADJUSTING THE ENGINE IDLING SPEED". in your service manual 6. Adjust carburetor synchronization. A. (Fig.3) Synchronize carburetor #1 to carburetor #2 by turning the synchronizing screw (3) in either direction until both gauges read the same. NOTE: After each step, rev the engine two or three times, each time for less than a second, and check the synchronization again. B.Synchronize carburetor #4 to carburetor #3 by turning the synchronizing screw (2) in either direction until both gauges read the same. NOTE: Turning screw clockwise raises carburetor #4 and lowers carburetor #3. C. Synchronize carburetor #2 to carburetor #3 by turning the synchronizing screw (1) in either direction until both gauges read the same. NOTE: Turning screw clockwise raises carburetor #3 and lowers carburetor #2. Vacuum pressure at engine idling speed is 37 kPa (280 mmHg). NOTE: The difference in vacuum pressure between two carburetors should not exceed 1.33 kPa (10.0 mmHg, 0.4 inHg). 7. Check engine idling speed. If out of specification, adjust. 8. Stop the engine and remove the measuring equipment. Yamaha then recommends the following. 9. Adjust: Throttle cable free play Refer to "ADJUSTING THE THROTTLE CABLE FREE PLAY". Throttle cable free play (at the flange of the throttle, grip) 4 - 6 mm (0.16 - 0.24 in) 10. Install vacuum plugs.