Lurching would be from jetting or from your drive chain being too loose. The latter is very common. Due to KTM's chain slider setup, excess chain slop isn't always immediately noticeable.
1979 GS750E for sale HERE
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2005.5 KTM 950 Adventure
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1989 Chevrolet Caprice Classic Wagon, TBI 5.7, NV3500 5-speed, lowered, etc...bike hauler