What are the reasons for abnormal noise in the CFMoto 250sr engine?
2 Answers
The reasons for abnormal noise in the CFMoto 250sr engine are as follows: Excessive clearance between the piston and cylinder wall: Over-tight assembly of the piston pin or connecting rod bearing; excessive clearance between the tappet and its guide hole; wear of the cam profile; sometimes, the starting claw is loose, causing the pulley to make noise (more noticeable during speed changes). Excessive valve clearance: Excessive clearance between the tappet and its guide hole; wear of the cam profile; excessive clearance between the valve stem and its guide; broken valve spring; radial cracking of the camshaft timing gear; loose valve seat ring; valve sticking and unable to close. Excessive clearance between the piston and cylinder wall: Incorrect depth and width of the main bearing oil groove; low oil pressure leading to poor lubrication.
I've ridden the CFMoto 250SR several times and encountered engine noises, usually caused by a loose chain tensioner, which sounds like a clicking noise. If the chain is too loose, it can rub against parts, or if the valve clearance changes and the valves aren't properly aligned, it can also produce a rattling sound. Additionally, insufficient lubrication can cause severe dry friction in the engine, leading to increased noise. I recommend stopping to check the chain tension and oil level first—if it's too loose, adjust the tensioner; if it's low on oil, top it up. Don’t overlook cooling issues, as high temperatures can cause metal deformation and abnormal noises. Get it checked at a shop as soon as possible—small issues can turn into big problems if ignored. These kinds of noises are quite common in single-cylinder engines, and regular maintenance can save a lot of hassle.