Starting
Yep, lower cranking pressure for easier starting. May need to address denotation also, but I need to run it more to see if the plugs still loosen up. Above all else it needs to be reliable.
I have to apologize. I've been busy and really didn't think this problem you have through.
Hard starting:
You have a couple of choices. They're both going to change the way the motor runs on the very bottom end only.
To lower cylinder pressure for starting, cutting exhaust valve further back will work but not my preferred way as when wide open doesn't fit flush on top of
your nice ported exhaust port . It will work, just disturbs flow .
The other way I have not done on an older Polaris. On the Skidoos I put a spacer inside the bellows that physically stops the valve from going down all the way, but, valve still fits flush on top @ WFO.
You can play around with different lengths on the spacers to get it where you want.
Note:
You are going to notice it might be more "marbly" on the bottom end as this obviously changed your port timing at the bottom only. The engine will want to " 4 stroke " to a higher and higher rpm as you raise the valve up under light throttle no load. It's a trade off cruising on the trail but man do they ever start easier!!! You will be amazed how little you might have to go.
Good luck>>>>>