Acceleration poor

15 General causes

12 Weak spark at plug or erratic firing

Battery voltage low. In certain conditions low battery charge, especially when coupled with a badly sulphated battery, may result in misfiring. If the battery is in good general condition it should be recharged; an old battery suffering from sulphated plates should be renewed.

Spark plug fouled, faulty or incorrectly adjusted. See Section 8 or refer to Chapter 3.

Spark plug cap or high tension lead shorting. Check the condition of both these items ensuring that they are in good condition and dry and that the cap is fitted correctly.

Spark plug type incorrect. Fit plug of correct type and heat range as given in Specifications. In certain conditions a plug of hotter or colder type may be required for normal running.

Faulty ignition coil. Partial failure of the coil internal insulation will diminish the p^Hormance of the coil. No repair is possible, a new component must be fitted.

Pickup coil faulty. Partial failure of a pickup coil internal insulation will deminish the performance of the coil. No repair is possible, a new component must be fitted.

TCI (igniter) unit malfunction. See Chapter 6 for details.

Ignition timing reluctor loose on crankshaft end. Re-secure the reluctor in the correct position.

13 Fuel/air mixture incorrect

Intake air leak. See Section 11.

Mixture strength incorrect. Adjust slow running mixture strength using pilot adjustment screw.

Carburettor synchronisation.

Pilot jet or slow running circuit blocked. The carburettor should be removed and dismantled for thorough cleaning. Blow through all jets and air passages with compressed air to clear obstructions.

Air cleaner clogged or omitted. Clean or fit air cleaner element as necessary. Check also that the element and air filter cover are correctly seated.

Cold start mechanism in operation. Check that the choke has not been left on inadvertently and the operation is correct. Where applicable check the operating cable free play.

Fuel level too high or too low. Check the float height and adjust as necessary. See Section 7.

Fuel tank air vent obstructed. Obstruction usually caused by dirt or water. Clean vent orifice.

Valve clearance incorrect. Check, and if necessary, adjust, the clearances.

14 Compression low

See Section 10.

All items as for previous Section.

Accelerator pump defective. Where so equipped, check that the accelerator pump injects raw fuel into the carburettor venturi, when the throttle is open fully. If this does not occur check the condition of the pump components and that the feed passage to the pump is not obstructed.

Timing incorrect or not advancing. Other than as a result of the pickup coils becoming loose incorrect timing is only likely to be caused by TCI unit failure. TCI unit failure will also prevent correct ignition advance as the engine speed increases.

Sticking throttle vacuum piston. CD carburettors only.

Brakes binding. Usually caused by maladajustment or partial seizure of the operating mechanism due to poor maintenance. Check brake adjustment (where applicable). A bent wheel spindle or warped brake disc can produce similar symptoms.

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DIY Battery Repair

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  • luigina
    Can xj650 pickup be repaired?
    2 years ago

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