spock58

You need to check the wheel bearing near the brake - they often fail.

If your Yamaha is cranking over fine but hasn't got spark, it's usually the stator. CDI modules rarely fail. There are tests you can do with a multi meter on a stator but not on the module usually.

Those quads use a fuel pump in most models and can often fail. They can leak fuel and run really rich or do almost nothing and run dry - not always easy to notice the diff. First thing to do though is change the sparkplug if you haven't already - it's a cheap fix for lots of quads!

There's only so much you can adjust, mainly the idle speed and idle/low speed mixture - there's a couple of screws involved. What's your issue, what do you think needs adjustment?

Nope, the decomp lever would only be required when pull starting - the electric starting issue may be just that your battery is low. Need to do a load test on it.