I have just made a 4 foot dirt ramp across the road in the bush and I can't get the speed to clear it. You see it is all sand and only about a 10 meter run up. Any ideas on how I can get the speed I need?

Lay some carpet down.
Build a roll-in.

Carpet and roll-in will cure you as stated above^^^^

Haha, its funny coz there is some old **** over here and a roll of carpet is here. I just rolled it out and it seems to be a lot better, thanks

did you try a roll in? that would give you even more speed and then you could get some wicked high air haha

I have a lil 2foot wooden ramp over there for that =)

Get a bigger front sprocket by one or two teeth.

by one or two teeth? try going up to something like 44-16 gearing... i know not everyone does that anymore, i dont, but i used to and you can go sooo fast with a gearing that big. its insane.

I am running 44 16

Perhaps you should have thought it out before building it with such a small run-up.