New guy here need help with 91 YZ125 Carb??

[je1377]

I just acquired a pretty nice 91 YZ125 that has been sitting for a few years. Pilot jet was stopped up so I cleaned carb , fresh gas and fuel/air filter and new plug. Bike fired right up but would not idle and is extremely rich and sputters above half throttle. I decided to go back through the carb to make sure no passages were clogged or I missed something. I started the bike and it ran great.
I rode the bike around my shop and when I came back in it went dead as soon as I let off the throttle. I went to adjust the idle and the idle screw and air screw had both blown out of the carb. Apparently I didn't tighten the idle and the air screw was out 2 turns. It shot them out in my shop floor as soon as I started it. I put them back in and the bike runs pig rich just like it did the first time. Ran great with them out.
Is this a jetting issue or should I check something else? This is my first two stroke bike. Previous owner said it ran absolutely fine when it was last parked. It has a pro ciruit pipe and dg silencer. I did notice the airbox has two 1.5 inch holes in the right side that I'm not sure are factory or not. Thanks for any help in advance.

 

[arnego2]

I couldn't care less what a previous owner tells me, no receipts means BS.
No hassle to have a look into the cylinder and just see with your own eyes if the topend is shot. Specially on those old bikes the piston might even be new but the bore is at its very end of lifespan.

 

[livefast]

similar thing just happened to my 03 yz250 and something with the carb wasnt fully seated. i was boggled, thought it could be a leaky base gasket, that wasnt it, thought it was a possible right side crank seal, that wasnt it, carb was clean etc....just a dumb seating problem. i brought it into the shop so when i see it and get some details ill let you know anything that could help