That screams "unmetered air" to me.
As the idle speed returns to 650 after a quick blip on the throttle, the A/F ratio is off. Anything above idle speed will mask this.
The entire top half of the motor should be sealed. Valve cover/grommets/oil fill cap gasket/dipstick tube gasket/side cover...
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.