Adjustment
1. If the engine runs extremely rough at idle or continually stalls, and if a carburettor overhaul does not cure the problem (and it definitely is a carburation problem - see Section 6), the pilot screws may require adjustment. It is worth noting at this point that unless you have the experience to carry this out It is best to entrust the task to a motorcycle dealer, tuner or fuel systems specialist. The front cylinder's pilot screw is accessible from the right-hand side of the carburettor assembly and the rear cylinder's pilot screw is accessible from the left (see illustrations). Make sure the carburettors are synchronised before adjusting the pilot screws (see Chapter 1).
5.1a. Pilot screw (arrowed) - XL model carburettor
5.1b. Pilot screw (arrowed) -XRV model carburettor
2. Before adjusting the pilot screws, warm the engine up to normal working temperature. Screw in the pilot screw on both carburettors until they seat lightly, then back them out to the number of turns specified (see this Chapter's Specifications). This is the base position for adjustment.
3. Start the engine and reset the idle speed to the correct level (see Chapter 1). Working on one carburettor at a time, turn the pilot screw by a small amount either side of this position to find the point at which the highest consistent idle speed is obtained. When you've reached this position, reset the Idle speed to the specified amount (see Chapter 1). Repeat on the other carburettor.
Caution: The catalytic converter fitted in the exhaust system of XL650V models may be damaged if the air/fuel mixture is maladjusted.
Restrictions
4. Due to the increased emphasis on controlling exhaust emissions in certain world markets regulations have been formulated which prevent adjustment of the air/fuel mixture. On such models the pilot screw positions are preset at the factory and in some cases have a limiter cap fitted to prevent tampering. Where adjustment is possible, it can only be made in conjunction with an exhaust gas analyser to ensure that the machine does not exceed the emissions regulations.