I have a V-twin that runs OK, not great, no idle and have to accelerate very slow to keep from dying out. More I run it, better it responds. Been running cleaners thru the 2 barrel carb it has. Tractor had a deck on it and when I tried to engage it dies off right away. Thought it was frozen spindle or other issure. Everything is loosey on the deck and pto engage. I finally babied the engine to stay running if I run slow and slowly slip the pto in to engagement. It will run some, but with no power and you can't mow 5ft w/out it dying out again. I'm wondering if somehow one side is not sparking or running at all even?? Seems to run fine when just setting and revving up and such. SO, I'm waiting to see what You come up with for your problem, which may also be mine then. Sorry, not gonna be able to help, but will be watching this post for any ideas. Maybe I should check my valves? It is OHV, so should be easy right? Never have been into an OHV engine yet.