With some background first.
Upgraded to 7springs clutch. Removed rib on case clutch cover.
New 3 plates clutch disc. Soaked over night. SAE80 gear oil. New basket. New separate bush and pressure washer. Clutch separate test is good. There is a washer between the crank bearing and 0.5mm gap to the clutch gear.
Clutch disengage and engage fine. Gear change is fine. Roll free in first gear. The problem is only when start moving from stop in first gear the engaging is not smooth and create loud grinding noise. The bike will suddenly lurch forward no matter how slow I release the clutch level. As soon as the bike is moving then 2nd / 3rd gear the problem gone.
If I step on the rear brake, in first gear, give it little throttle and release the clutch in half way, clearly hear the grinding noise and the bike wants to jump forward (instead of pulling forward).
I removed the clutch again and again did not see any grinding marks or abnormal sign. Exchanged 2nd set of new clutch plates behaved the same.
I researched online everyone said itís the oil, dry clutch plates, soak the plates, cable adjustment, even primary Cush drive. I have actually upgraded to DRT 23/62 so itís new Cush drive.
Anyone has some ideas to help me to determine what caused the problem? Much appreciated.