Your right they're not shearer pipes. They have the name engraved on the mounting bracket. I might guess they could be Vito fat bastards? But I have never seen them in person so I could be wrong
Ignition coils rarely fail. But the sometimes do. Definitely check your plug caps too.
Hard starting like your referring to can also be a sign of low compression. Do a compression check as well.
The hanging idle could be a sign of an air leak somewhere. So I'd recommend doing a leak down test.
These are the things I would check if it were me.
Start with plug caps. Then check coil and plug wires.
High idle, check carb sync and idle settings. Could be cause of your problems too. Also it could be an air leak. Do a leak down test too.
Float height? Not sure what spec is but you mentioned it helped. Really seems like a rich condition as it ran better as the bowls emptied.
Keep in mind as you use less oil in the premix you are richening your air/fuel ratio as well.
Will it Rev out if you take the pipes off and run it briefly?
Fast told me to jet rich. Needles full rich. Don't even bother with a carb sync. Take it out and warm it up and then ride it full throttle then let off, full throttle then off. Do this for about 20 minutes or so. You have a short window of time to get the rings seated in with the fresh cross hatching.
This is also what was taught at the motorcycle mechanics institute.
I had a cheap ass o ring chain once. Can't even remember the brand. But it broke and went flying off in the woods some where and I had to walk back like 6 miles back home. I recommend spending the money on a good name brand chain.
How sure are we that it was an air leak?
I've been dealing with this pretty regularly. 4 rebuilds... all within a couple of hours or less of riding. Every rebuild requires new cases and crank as well as cylinders refurbished. Im honestly thinking that its a loss of fuel. Im to the point where I dont think the hole in the fuel cap is drilled out big enough.