Starting problem

[D12]

I have this problem since 3 weeks... i ride my bike usually 2 days a week.. i own a 2003 400ex. (bone stock) except that i have a 450r slip on, but i don't think it change something to my problem... when i want to start my bike... the engine crank very slow... my battery seems dead... then i start my quad on compression.. after 30 min of riding... my battery is fine and the bike start fine... so before changing my battery should i check something else or the problem IS my battery ?

thanks in advances..

[Franky G]

Mine does the same ting I just changed my baterie to a baterie with more cranking amps and now it works just fine hope this helps you