This year, 2012, I bought a very first scooter in my life, Yamaha Riva 125 with 22000 miles on it. High mileage scared me but it seemed have been well taken care of. 300 miles since I got it, the intake valve got stuck and it was bent. Got new valves, in and ex, installed after the head was cleaned and inspected. There were cracks on intake valve guide which were visible. I thought it will be OK. 100 miles after new valves installed, the two valves decided to hit each other. So, this time, I got used cylinder head with valves and other parts still installed. The intake valve shows un-even heat transfer. The head was disassembled and cleaned before installation. Now, the scoot is on the road and has two issues. Starter clutch does not engage on first try, on occasions when hot. It catches eventually, and I can be on my way home. I know this clutch should be replaced soon. Second issue is the engine coughs when at steady speeds between 35 to 45ish miles. A few times, I had the engine quit on me when I was decelerating for stop light from 50+. At about 40ish, I lost engine and had to coast to stop. When this happens, I have to wait like 1 to 2 minutes before it starts again. Does any one have any idea? Carburetor needs cleaning and adjustment?