I think the 30 watt unit will very under powered to due a good job and most will have tanks too small for most small engine carbs anyway. The one I am using is 160 watt version by Kendall and it usually take about 30 minutes to clean most carbs; which is four long cycles. Longer cleaning cycles can be used if necessary without the damaging effects that the soak carburetor cleaner has. Plus it don't take an overnight soak.
I originally got it to clean 2 cycle carburetors due their delicate construction with non-replaceable check valves but I now clean all my 4 cycle carburetors for engines up to 30 hp. Most time I use just about 2 tablespoons of household liquid dish cleaning soap in one tank of water. Using the heat greatly improve cleanings.
I do pre-clean the carburetor exteriors to get rid lose grime; although not necessary, but it does makes cleaning easier.
In the last two years I have had only one carburetor I couldn't clean using it and was cause an extreme case of rust in the passages caused by a metal gas tank on a 1966 Briggs engine.
As for the cost the unit here it was about 100 usd but that can easily offset the cost 4 buckets of the soak cleaner and the time wasted waiting on the soak to do it job. On top of that our EPA is beginning crack down on our disposal of the hazard carburetor cleaner.
