xr 440 question

[flybytaco]

i just installed a 440 kit in my freinds xr and a rev block and ran 110 race fuel and when its at about 3-4 throttle it pops any advice?

 

[IrishEKU]

"Pops" (read) backfire?

If so the jetting is off. That would be my guess, if you haven't already, dial it up a bit with some larger jets to compensate for the extra .40. I'm sorry but I don't know the #'s for Honda Carb's.

Good Luck!