timing off?

[gs850cafe]

so i went on a rather long ride today...around 250 miles round trip to be exact...

going oh about 35-40 in 5th gear..if i open it wide open or 3/4 it sound like a rod knock(or loud sprak knock?) for just a second...sometimes i head it taking off kinda slow...i rarley hear it..but now i wanna know what it is

bike is 81-850 an i run 91 octane (no ethanol)

[FLHGSRay]

Sounds like spark knock. Check the timing with a light and check that the advance is working.

[rustybronco]

Like Ray, it sounds like spark knock. 35~40 in 5th and you're opening the throttle that hard? Next time downshift it into forth then whack the throttle, you're lugging it.

[gs850cafe]

i kinda figured it was spark knock..ill check timing soon as i get free time...also ive got bigger main jets...i dont ever recall it doing it before the jetting(just have 4-1 header with baffle)