70cc flat spot...21mm carb jets advice required please

[niceday]

Hi, my son has just bought a Rieju fitted with a 70cc AM6 engine, 21mm PHBG Dellorto carb and Metrakit exhaust that had seized with head o-ring blown too. Just fitted a new piston and rings (cylinder was ok luckily) and given the carb a total clean, new spark plug, clean air filter. Problem is, great at idle and small throttle but bogs when throttle opened. Revs then build very very slowly until 10,000rpm when the machine takes off like my GSX 600 (almost!). Any idea what needle and jet sizes should be please guys. Happy Xmas to all.

[niceday]

Also, does anyone know what the cylinder pressure should be using a compression tester on this engine? Just ridden it and could be a blocked exhaust, oh the joy of working in the ice!

[Ariel Badger]

Try raising the needle as that is were the problem seems to lay, she goes up to 1/2 opening and again after 3/4 and that is needle territory.
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[niceday]

ok, thanks, will try hat tomorrow. It is currently on the second notch down so will try one notch more. I was told that the bike used to run well but having doubts about that lol. Taken the silencer off and it is well coked up, runs a bit better, especially when revs creep up to 8000. Does seem like carb problem.