honda cbr 600 1998 problem rev counter drops to zero

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i have a honda cbr 600 1998 ive had it about 2 months the problem is that whem im riding it i get 4 about a mile when the rev counter will drop to 0 4 a split second then back 2 normal rev when the rev counter drops the bike will will slow dowd asif i had pulled on the brikes this will continue every few feet. Whem im in a low gear the bike will cut out completley this will somtimes happen when i pull in the clutch sometimes it will start agane straight away other times i have to lave it 4 awhile be 4 it will start agane iv changed the in line fuel filter and spark plugs and air filter this happens at about 4000 to 5000 revs at first then at any revs at all. I all so changed all the fuses i even disconnected the sade stand switch but nun of this has help i im assumeing it is an electrical problem.i just do not now what. can u help with some iders thank you