The factory pre-sets are not always the proper Needle settings for the engine. Its sounds like your enigne is rich on the top end. If you are using factory settings for the High Speed Needle and only running 15% nitro this could be the case.

To be honest I have never taken one of the external regulators apart. I don't know how. Sorry Contact Richard at YS Parts and service if you really think the regulator needs to come apart.

Personally I think its a mixture setting.

Perhaps trying some higher nitro content would help you get the settings closer.

Troy Newman
Team YS