Ask The Editors: Symptoms of Valve Clearance Trouble
Tic. Tic. Boom.
While you don’t specify the types of power loss you are experiencing, the short answer is yes; valves that are out of clearance spec can certainly result in a loss of engine power.
You’ve already discussed the most common sign of valve issues; a tapping or ticking sound coming from the engine. From there hard starting, especially when the engine is hot is another common symptom. Notable power loss, especially as the ATV heats up from use may also be experienced.
If the intake and exhaust valves are out of spec, you will likely experience rough idle or sudden bogs. Other signs to look for may be a sudden decrease in fuel economy.
Generally speaking, when your valve clearance is on the loose side of spec, components of the valve mechanism hammer together, damaging the valve and creating that knocking or rattling sound we mentioned above.
Clearances too tight, on the other hand, can prevent the valves from completely closing (or not closing for a long enough period per cycle) and are more prone to heat damage and eventual valve failure.
If in doubt, get them checked.
