Running

[Ajaydave]

Just started my mod 31 after a while, took for a bumble, if I accelerate at fifty it pulls back, but if I let it creep up it’s okay, I thought weak, but plugs read okay, any ideas folks, it chatters from the drive side as well quite loud,

[dave16mct]

Could be some muck under the main jet, being sucked up and obstructing it when you give it throttle. The chattering's a bit more worrying though. Could just be mushy clutch rubbers, loose chain or rotor nut. But if it's coming from the N/S barrell remove it and check the gudgeon pin isn't seizing causing the piston to tilt and chatter against the bore. This happened to me and it seized up in a big way causing horrendous damage needing a complete strip down.
Dave.

[Ajaydave]

Thanks Dave, I,ll check for muck in float chamber, , also take off primary and check , I wondered about jet size, I,m running 2 into 1 with a mega, rgds, D

[dave16mct]

No, not the float chamber, just remove the nut at the bottom (to expose the main jet) . There may be something in there. I've seen a small piece of wood once and another time a mate had a stringy length of PTFE tape which both gave the same symptom as yours. When he opened the throttle it didn't want to go because it was being sucked into the main jet.
Dave.

[Ajaydave]

I,m running a concentric carb, think I,ve got jetting right,