THE CHOKE OF MY SUZUKI 2004 Z250 HAS TO BE ON IN ORDER TO USE IT. WHAT WRONG?

Question edited for clarity.
Question moved to Suzuki.

Normally caused by cracked return springs or bent selectors, but in your case, it's not. There is a shift kit available to fix the issue because it is well known.

http://www.factorypro.com/prod_pages/prods,rm-z250,07-13.html

https://www.google.com/search?q=2006+suzuki+rm-z250+shifting+problems

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Yes, completely normal. The choke is also known as an 'enrichment lever' and adds a bit of fuel to help cold engines start. When temperatures get up into the 80F range you may get away without choke, depends on how well your carbs are set up.

Most of those answers are wrong. When the choke on you are making your air/fuel mixture richer. So your bike is saying it wants more fuel or is getting too much air. If you have not modified the intake odds are it is a dirty carb. Remove and clean it. All of the jets need to be perfectly clean.

I have included a pic of a suzuki z250 carb with some parts hi-lighted. Please note that not all suzuki z250 carbs are the same but I hope this helps you :)

To rich adjust the carb

no fuel filter ,only have fuel strainer on the fuel valve(fuel tape) in to fuel tank

Google ' suzuki service manuals '