I Have an older 3250, by that I mean Italian made. It was broken in and then put away until I got it. It runs very weel turning a Zinger 18x10 at 7400 on powermaster 5%. However, after about 20-30 seconds at full open it wont come back to idle. It seems to hang around 3400 or so. My idle is about 23-2400 and it transitions really well. It sound like its going lean when I come back to idle. It takes between 15 and 30 seconds to come back to normal idle. I changed to the OS carb but it didnt changes at all. The only way I could make it work was to set the idle mix so rich it wont transition well. Anybody got an idea? Oh yeah I even changed to a cooler plug thinking it might be a heat issue after the higher rpm.

Usually, if the engine takes a while to come down to idle when you close the throttle, the idle mixture's a bit too rich. The idle should be set only after the high-speed needle's leaned to just rich of peak RPM. You may also need to rotate the spraybar a hair.

Fuel should be 5%-10%, oil can be 10%-12% once the engine's had a few gallons of regular fuel run through it.

Please see the thread on setting the carburetor that's one of the "sticky" messages at the top of this forum.

I took the ST carb off and cleaned it, I havent reinstalled it yet. I've got the OS 7D working good after an hour of tinkering, I had to richen the low end almost as far as it would go? Thanks for the info I'll keep working on it.