- Sat Aug 05, 2017 9:54 pm
#69805
The carb needs to be tuned (pilot air adjustment & idle speed) with the engine at operating temp. If you try to optimise pilot air settings and idle speed with a cold motor, the setting will be too rich, and the motor will be inclined to stall when hot.
In the floor of the carbs throat, there are two tiny wee holes; Pilot outlet, and pilot by-pass out let. Those wee holes, must both be clear to allow correct function of the pilot air screw adjustment...
You will need to blow compressed air through the pilot air inlet in the mouth of the carb, whilst observing the two small outlet holes...
Alternate is to squirt petrol (syringe) through the Pilot air inlet and watch to see the fuel exiting.
Note; when attempting to verify clear pilot circuits it is advised to block the pilot FUEL inlet in the under side of the carb body with a finger to maximise the flow of petrol/Air through the pilot circuit so that it is obliged to pass via the both outlet holes...
The std pilot jet supplied in most Amal carbs (#25) suits most all 4 stroke street bikes. It is unlikely that you would need to change the pilot jet for a basically stock bike unless either the air screws is set to less than 3/4 a turn out, OR more than 2 turns?
Basic starting point setting of the air screw is 1 3/4 turns out, screwing in richens the mixture, out weakens.
Motor hot, idle speed set too high, (approx 1000 - 1200rpm) slowly turn OUT the air screw 1/2 a turn. Does the idle speed increase? Does the idle start to become erratic?
Next slowly turn the Air screw in 1 turn; does the idle speed drop? Does the exhaust note deepen? You are seeking a mid point between those two responses that the engine provides you as feed back...
The setting of the air screw you seek will have the fastest, steadiest even speed. Then slowly reduced the idle speed 1/2 a turn and fine tune the air screw once again...
Repeat the process...
Blip the throttle, several times. IF the carb 'spits' (weak) at you, turn the air screw in another 1/4 turn (enrichening). IF the motor 'spits back' upon acceleration on the road, you will need a richer Throttle slide...
IF at idle there is any 'Poping' in the exhaust and erratic engine response, double check ignition timing is not retarded (reduced points gap).
IF your exhaust header pips is deeply blued, the ignition timing is/has been retarded...
When all is set correctly, and with a hot motor, the Bullet can be started by HAND.
Factors that will effect idle; to large a plug gap, incorrect heat range of plug, carb manifold gasket, float bowl gasket, weak battery, low compression, excessive oil consumption.
