Most times when your engine won't decelerate (hangs up at a higher rpm for a few seconds)before settling down to an idle, means that the low needle is a bit lean. Properly tuning a carb is not rocket science and if done correctly the engine will thank you by performing well. For finding out exactly how your carb works and how to tune it visit the RCGF engines web site and under the heading 'Articles' you will find all the info you need to do it correctly or use the Search feature on this forum and do a search on Tuning a Walbro carb, and keep us posted on how things turn out.

Karol