By: Anonymous: Bob () Sunday, 26 May 2013 @ 08:28 AM ICT (Read 1555 times)
I recently purchased a second hand Yamaha FZ6 that has 35,400 kilometers on the odometer. It is in great condition, the compression is good on all four cylinders and it uses no oil. My concern is that even though the redline is at 14,000rpm, the previous owner never really took it over 7,500 to 8,000rpm. Since the real power just begins down in that rpm range, will the engine be damaged if I now start revving closer to redline?
By: ThaiDesign (offline) Sunday, 26 May 2013 @ 10:38 AM ICT
Not at all. Running an engine at rpm levels that are only around half of its maximum rev limit doesn't cause any conditions that would result in component failure when the engine is spun up to redline. Your favorable compression test and the lack of oil consumption is an indication that the engine is in good shape, especially since you didn't mention it making any unusual noises or exhibiting any abnormal performance behavior.
When developing new models, the manufacturers run the engine on dynometers at peak power and redline rpm until something fails. After making the modifications necessary to strengthen the affected component, they repeat the procedure all over again until they are satisfied that the engine can withstand the rigors of operating at those rpm levels without catastrophic failure.
So, given that your Yamaha FZ6's engine has survived those kind of durability tests during its development, running it at thousands of rpm lower than its maximum rev limit does no damage, and neither does spinning it up to or near redline.