my gsxr 400gk76a wont run quite right

[babygsxr]

When i run it up it shoots the little cap of the number 1 carb where u balance them and wondered if any 1 had any idea wot this could be caused by

[Nope.]

I dont quite understand your problem. Can you possibly describe it too me more clearly and with proper english please?

99% of problems with the GK76A not running right are caused by the carb seals going bad. Does the bike run lumpy, not idle or not rev properly?
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Former: Derbi GP1 50, Sachs XTC 125, Suzuki GSXR 400 GK73A, Kawasaki ZX7R, Suzuki DR250, Yamaha RD350
Current: 2011 Yamaha XT660Z Ténéré, 2003 Yamaha YZR-R1 5PW (In Build), 2009 Kawasaki ZZR1400

[babygsxr]

Do you know on the carb tops it has the small tube that the balancing guage attaches to so you can balance the carbs. on the carb on the left if you are sat on the bike it pops the little cap that covers the balancing tube off when it runs for a certain amount of time

[babygsxr]

The bike doesnt rev very well either

[Nope.]

Thankyou.

It sounds like you need to strip down and clean out your carbs and order some new O-rings for them.

https://www.400greybike.com/files/The_Mikuni_carbs_on_GK76a.pdf

That should help you out in obtaining and replacing the correct parts.
____________________
Former: Derbi GP1 50, Sachs XTC 125, Suzuki GSXR 400 GK73A, Kawasaki ZX7R, Suzuki DR250, Yamaha RD350
Current: 2011 Yamaha XT660Z Ténéré, 2003 Yamaha YZR-R1 5PW (In Build), 2009 Kawasaki ZZR1400

[babygsxr]

Nice 1 for that