Two-stroke mis-mixture

In my haste to get the job done quickly, I mixed a batch of 2-stroke mixture by eye & seem to have used too much oil (1 : 30) is the normal mixture.

The engine starts and runs a little smokey on low revs but won't throttle up enough to use effectively (it is a strimmer).

Unburnt fuel seems to be the problem since the spark plug was oily until I cleaned it up (in petrol).

I have replaced the fuel with the proper mixture but the problem persists.  Can anyone please offer advice on what I need to do?

i would have thought that it will be a dirty air filter (blocked with fuel+oil) or could be a blocked exhaust port (build up of carbon deposits)
both problems are very easy to fix.
wash the filter in a bit of clean petrol and dry with a rag, and give it another go.
if that don't work you will need to remove the exhaust, and clean out the exaust port. but before you do that give me a shout and i will lead you through the process.