Thanks for letting us know, Paul. I can't think how both valves could suffer from reduced clearance without there having been foul play (somebody messed with the adjustment) or a disaster that is in its early stages.
Has anyone been at the valve clearance adjustments previously?
Is there any sign of damage to the cam lobe and/or crud building up under the cam followers?
If it is neither of those causes, it sounds a lot like valve recession - most other kinds of wear cause valve clearance to increase, not decrease. Valve recession should only happen over a very long time (it should take as long as it takes the rest of the engine to wear out), or after long periods of over-revving the engine. (Having said that, lots of engine manufacturers grapple with the problem from time to time, on one model of engine or another.) It would be interesting to know what caused the problem, in case it is a characteristic of the GX25 (and perhaps the GX35 as well).
