Motorcycle Repair: starting problem, minuites, back fire

Question
Hi Chris
like to ask your opinion
have a gsxr 750 1996 carb model
just latley have problems starting , it cold here at moment so normally choke out ,no throttle and it will fire and run no prob.
but Now will spin fine might catch weakly then stops.
Trying to start again just spins fine might fire but once starter released will stop.Good for a few minuites of this then battery gets slugish.
Have charged battery so seems fine.
also might get one back fire at the end of all this trying to start.
If i bump it usually starts but not an easy bump.
have taken to using jump leads from car, which will spin it after my battery gets run down,and it will then usually fire up after 20 secs.
Bike has been stored a few times in last couple of years but have been riding for 6 weeks until now no probs.Also has suffered with carb icing but seem ok now.
Cant think of any other facts that my help.
Havent checked anything yet will have to wait till weekend.
Have a few ideas what may be wrong , so wellcome your input.
Cheers mike  

Answer
Hi Mike.
 It sounds like you are suffering from varnish in the carbs.  Start by pulling the carbs and giving them a proper and thorough cleaning.

After that, do a full tune-up on the bike and you should have the problem licked.

Let me know what you find.

Good luck.
FALCON