Make sure you didn't allow the chain to rub through the oil seal for the swingarm pivot (like I did!). Then you will have to partially remove the swingarm to put in new seals and bearings anyway. The swingarm does not need to come all the way off the bike, fyi
Do a compression test. If that is fine, switch the plug wires around and see if the problem switches sides. The lack of smoke could also be a lean condition on that cylinder.
Your compression will vary depending on your elevation, sea level is around 125psi for stock head. Under 100psi or a variance of 10% per cylinder is time for a bore and pistons. Hold the throttle wide open and kick until the gauge stops climbing. You may want to compare hot/cold data. Make sure your tester is not a POS.
There are several good threads on here about leakdown testing. 6psi for 6 minutes is pretty standard.
Sorry to laugh, but the scewdriver part cracked me up!
Sounds like you may have an airleak. Do a leakdown test when you gett'er back together, then run some plug chops to dial in your main jet.
I use R50, it is 100% synthetic. I have had no issues with it, burned about 4 gallons through the bike so far. It is nice because whenever I try to order Supertechniplate it is on backorder, but the R50 is usually in stock. And yes, it smells purdy
How long of a race? Sounds like he is setup for mx, while you have taller gearing. My bet is he takes you out of the hole. You catch and pass around 300'.
An impact wrench is your best bet for the flywheel nut AND the puller that you will need to get the flywheel off. Don't try to pull the flywheel with a 3-jaw. Make sure to use an impact or a torque wrench and an extra set of hands to put it back on. I've had them come loose before upon start up, not cool!