OK so ever since I rebuilt this 660 I have had a top end throttle problem. Sounds just like if you have a governor on in reverse. But this isn’t the case. So let me tell you what I do know so you won’t throw things at me that I’ve already done. First off I cleaned the carburetor. No restrictions in any office, plus the carburetor was relatively clean anyway. Second, timing is perfect without a doubt. Third, valves have been checked over and over again and they are perfect! There is a new stater, and a new CDI. I originally replaced the state are thinking maybe I had a weak spark at top end but no difference and then I thought maybe the CDI was acting up but no change with the new one. The only thing I have not physically changed is the coil. I have a video of me revving the engine but I cannot download it here. So if anybody is interested in the video send me your email and I’ll send it to you or a phone number. My phone number is 541-292-7688 my name is Tim ,I’ve been on here a long time but this one’s got me stumped! So I need somebody’s help.