ll I know is I have over $500 in my sons quad. I've replaced the crank, crank bearings, timing chain, timing. chain tensioner, timing chain guides, bored out the cylinder, new piston and rings. I've done all of the work myself. If I had to pay someone. It would easily be over $1,000. I'm thankful I don't have to replace valves. ( I replaced the valve seals last winter). And this is for an old reliable honda xr 400 motor.