Suzuki 2 Strokes

Hi i am a newbie on here and am having problems with my Suzy.When i got it it was a complete mess engine wise.It wouldnt start and when i opened it up found that one of the piston rings hadnt been fitted correctly and had popped into one of the ports on the barrel.you can imagine what it was like.So i have redone crankshaft bearings and seals,rebored barrels and new pistons and rings and reassembled it.But what is happening now is it starts fine on the choke but when you take it off it runs a bit rough.It will take over but when you try and rev it it struggles and i have to keep revving to get revs up.Once revs are high(about 3000)it will rev but not right.When i try and ride it it has no power.It seems to smoke quite a bit as well but it hasnt had a good ride yet only been sat in garage.It is a gt250A and is 1977.Also my fuel tap has two outlets on it and one of them has been blanked off and the fuel line has a tee piece in it is this correct.
Thanks,John

Did you clean/service the carbs?
Are the carb slides oriented correctly? The cutout should be facing the air filter? (This problem happens when you switch the slides.)

Hi Jabcb thanks for the reply.Yes the slides are the right way aroundand the carbs seem to be ok.I have been tinkering again to day and while i was emptying the petrol tank the flow rate started to slow,when i lifted the fuel tank cap the flow returned again. Could this be the problem.Should there be some sort of vent to allow air into the tank so as not to cause a vacuum.Plus im still wondering about the petrol tap i will try and get a photo up to see if it is the right one.
Cheers,John

here is a photo of the petrol tap

I had a 1973 GT250K with a petcock that screws on the same way as yours, and a later-model with a petcock that attached via two bolts.
Both were vacuum operated. Neither looked like your petcock.

Suzuki used a standard fitting on your gas tank, so there several different aftermarket petcocks that work fine. Most are manual, but Pingel sells one that is vacuum operated.

There is a vent passage inside the gas gap. Its designed so that gas doesn’t leak out as a result of it splashing around as you ride. You will have problems if that passage is plugged up.

The fuel & air passages in these carbs are rather small. Having problems because they aren’t fully clear is pretty common even when the carbs “look clean”. Your problem could be related to a plugged up pilot circuit.

Ah so the chances are this isn't the correct petcock as it is causing a vacuum in the tank. Will try it with the fuel cap open and see what happens. Thanks for the info, John

Update:tried fuel cap no difference. Fired up bike started running on one pot. Checked spark OK checked carb. It was still full of fuel in bowl seems like cylinder getting no fuel. Stripped carb again blew all jets and ports. Seemed like slider needle blocking off main jet. Had a spare needle changed it. Fired up and seems to run like a dream. Will test properly tomorrow. Fingers crossed