Get a new cheap and bad ass OS for it. Very reliable engines.

You never said it was a second hand engine in the first post.
Second hand engine, its likely piston and sleve. Half the reason people sell em is because there to lazy to re-build.lve picked up about 6 truck over the years just from, lazy people or, people who have given up on nitro, and that is usually because they find tuning an issue !