Do I need to replace the throttle spring?

I have a Honda Izy and the throttle does nothing. I bought it second hand and it was like this when I got it. I can adjust the speed by manually pushing the governor but using the lever does nothing. It seems that the spring is just not strong enough. I have moved it to the furthest hole but this made no difference. It could be something like the governor pulling to hard, or sticking, but when the engine is not running it sits back at the low rev position.
Any ideas would be very gladly listened to.
Thanks.