I would recommend a bigger main jet myself they dont cost much, I know the original was 130 but I dont trust modern petrol that much myself it's certainly not the same as it was in 1979...buy a 135 and a 140, fit the 140 first and if it doesnt bog down all well and good ...if it does then try the 135...thats what I'd do. Pistons are expansive...jets arent. If you do this dont buy pattern jets either, genuine ones from allens is the way to go