When I’m slowing down on my Honda CG125 and I’m in third gear, then go down to second, when I slowly let out my clutch I get a fast juddering noise. It seems to do it more when cold. The chain tension is good and the bike has recently had new sprockets. Divetime, MCN forums
CG125s should have their engine oil changed ever 750-1000 miles to keep things happy. The spring-loaded screen mesh oil filter also needs to be checked and cleaned if necessary. There is also a centrifugal oil filter on the end of the oil pump that should be cleaned periodically, but this one is more of aworkshop job. The clutch basket also has a rubber damper that can become worn and cause this problem, as can weak clutch springs (but that usually accompanies clutch slip). Also check that the engine sprocket spline hasn’t become worn. Check the rear wheel cush drive rubbers, too. If there's a lot of play in the rear sprocket, so you can move the sprocket more than a couple of millimetres with the wheel stationary, that could also be a problem.
If you're going to strip the clutch for inspection, you will need a Honda "castellated locknut" socket to remove the centrifugal oil filter from the end of the crankshaft, otherwise you can't get the clutch basket off. You can make one up yourself using a spare 20mm socket. All you need is a hacksaw, a file and a sturdy vice or improvise with a G-clamp. It will probably cost you 20 minutes of sweat and an old socket but it’s cheaper than the Honda tool and it works.