Hi Just finished an engine rebuild on my lads DNA50. Waterpump had leaked and rusted so while the engine was apart I changed the main bearings, crank and piston. Started up with a little help from some 'sure start' spray and idles beautifully. Then there is the snag. Engine is 50cc, standard variator with 5g rollers, clutch with white contraspring and 2000 shoe springs, new belt. Standard airbox, with brass inlet and cleaned filter. Standard carb' usually holds a 56 main jet. The only upgrades are a new stage 6 exhaust and obvious removal of the variator restrictors. Initially I put in a 63 main jet. The bike would tick over but any throttle would kill it. The plug sooted over. I reduced the main jet to 60, just 2 steps up from standard. Now it throttles up slowly but holds at 7000rpm (red lines at 10000). The bike pulls away slowly and the RPM creeps to 7000 and holds. If I throttle up to WOT the bike dies until I relax the throttle and it sits steady. I leaned out the jet needle and now the bike climbs to 7500rpm , doesn't die but wont increase in rpm. The pull away is slow but steady. The throttle is smooth, steady but lacks power and wont reach over 20mph or so. If I rev the throttle is a slow steady rev and no vroom, vroom. The bike slowly pulls away and feels like its lacking power. I figured it may be running rich still but when I remove the air filter then the bike wont climb over 6000rpm and gains no power. I need some advice as to whether it sounds like the jetting is too rich or too lean. Tickover - perfect Throttle up 0- 1/4 - slow, smooth, poor power and wont climb over 7500RPM (3/4 range to red line). Poor speed No Vroom 1/4 to 1/2, no change. Sounds like it slightly high revs for the low power. 1/2 - WOT - no change. Advice welcome
