My YZ125 Sputtering/Reving Problems???

[Danman2540]

Ok i have an odd situation....I have a YSR50 streetbike that i have put an '87 YZ125 engine into. The engine fit great and runs but just cant get it right. When im riding as the RPMs get to high end it sputters but if i let off the gas a little it smooths out (like too much gas i thought). The air/fuel screw was only one turn out so i backed it out a lil more and the more i take it out the sputtering gets better but it wont rev down. Like when i pull the clutch in it revs for like 30 more seconds. The only other thing i can think of is im still running the ysr50 pipe but only because the smallest part right before the silencer wasnt much smaller than the yz125 pipe. What should I do next? Does anyone know the stock setting for the air/fuel screw and stock jet sizes?

 

[viking20]

You need to run the 125 pipe , it will never run close to ok with the 50 cc exhaust.
It doesnt matter if you twist the pipe around if you have to because of clearance , but all of the cones and length from the front pipe will have to be there !
The silencer is less critical , but be carefull to run it for too long if it is too restrictive .....The engine will suffer...

 

[Danman2540]

Ok ill have to adapt the original pipe to the bike but still.... Does anyone know the stock setting for the air/fuel screw and stock jet sizes?
Thanks