i have got my bajaj pulsar 150 cc 9 months back, i too faced the same problem. i have taken to the bajaj service center where i have recieved a answer for my question saying that the volves inside the engine either might have bent down or there might be a breakage in that. he also said the engine has to be opened and the volves has to be replaced. some parts like gasket, spark plugs and volve caps should also have to be replaced. to stick back the opened engine we should get used by some paste also. i have get my bike done with that repair and now there is no leakage of the fuel.
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