Throttle problem

[MoWaterfowl]

I'm having trouble with my throttle after putting a bored 390 carb onto my Honda (genuine) 270. I move the throttle, but it doesn't take it until right at the very end and pretty much just opens the thing up completely.

I've uploaded a youtube video just so you can kind of see what I mean.

https://www.youtube.com/watch?v=9nNXWVA0Cuk

Any ideas? Thanks for the help!

 

[KartFab]

You probably have reduced the airspeed over the jet with a larger opening, which doesn't suck as much fuel through it as the pressure above the jet isn't low enough compared to the pressure under the jet, or... Could have a wrong size jet for the engine size....

Why not put the 270 carb on? It would work just fine then.

 

[OzFab]

First things first, it sounds to be running way too fast if that's idling; what's it like at lower RPM?

 

[KartFab]

If you look in the video, you can see the idle screw is screwed in all the way.

 

[MoWaterfowl]

Talked to a few people and pulled the jet out of the carb. It's a 92mm jet, which I'm told is probably too small and confirms KartFab's initial suspicion. Any suggestions on what size jet it needs? (Bear with me...I'm a computer guy, not an engine guy.)

Thanks guys!