Valve timing observations : 2 Skorpions motors

[hb7]

Both bikes bought new. Stock 2002 and 1998.
First motor (2002) run stronger,but, always burned a little oil ~.5 qt in 1000 miles. 60k miles on it.
Second motor (1998) not as strong (at the top end) no oil burning or very little at 1000 miles. 12k miles on it.
Both bikes are traffic warriors, ridden daily for errands and supplies.

I'm thinking the valve timing on the 1998 motor is a little retarded.
I'm considering opening it up and checking to see the valve timing.
It is possible the chain was not tensioned on the exhaust side when it was assembled.
Interested in any experience regarding valve timing observations on the stock motors.
Is there an adjustable cam sprocket for the 660 cc anywhere in the world ?
The stock sprocket looks like it can't handle being slotted. Not enough meat on it to cut.

What is the ideal cam timing set up for street ? using a degree wheel where would you set it ? TDC or + or - ?
Is a Hotcam stage 1 worth installing ? (if they have fixed their quality issues by now.)
Is there another stage 1 cam out there ?
Megacycle makes only stage 2.