Even though the secondary injectors aren't supposed to operate until 5500 RPM, I decided to run some tests to see if they were the source of the noise. No luck. I did, however, discover that the secondary injectorsstart operating at around 3500 RPM.

 

i have had no such knock. all i can say is check for proper chain tention. i had too much slack in mine and it sounded like a knock at low speeds in 1st gear. set proper tention. knock went away. but im sure you are all talking about engine top end noise.