Just had this SC500 given to me by coworker. It was her husbands who unfortunately passed away a few years ago. 
Hasn't run in 20ish years. Tank looks good inside and overall its in decent shape since its been in a garage. 
I was a motorcycle mechanic for 10 years but I almost never worked on 2 strokes. 
I've read the ignition systems are an issue on these. It came with a box misc ignition components so im assuming that was giving him issues. 
I see a couple companies that make full systems, anyone recommendations? 

I'm excited as raced one back in the day albeit briefly as i preffered my usual 250 but the 500 wasa great on fast open tracks. Anyway, lets see if she'll run. Check spark. Flush the carb but might need total dismantle & components cleaned & prodded. Check its got oil in the transmission, think might be a long dipstick on those but have bike about vertical. Be damn sure the throttle is opening & shutting nice & freely. Choke on & NO Throttle untill sign of life at least. Yeah they were weak in the spark department. By memory someone where i am in NZ used to rewind the source coil to a higher value. All a 50 year old blurr is 'that' lol. Best of luck.

Unfortunaly I don't have spark. It came with a milk crate of carbs, stators, rotors, a cdi, and a couple coils but I'm debating if I start troubleshooting or buy a better setup.
www.regulatorrectifier.com/products/1973...or-cdi-flywheel-coil
I found a post where someone says the IT400 improves reliability and tones down the advance timing to make the bike more rideable.  
Can anyone confirm that or know anything about the newer setups like the one i linked?
 

 In my opinion you need a heavy flywheel on that motor. I can't imagine trying to start one without plenty of flywheel inertia. In saying that I think I recall someone on here using similar to your link so hope they come on if I'm thinking right. I'd think an ordinary late DT400 or "79 DT250 flywheel cdi would bolt on. Good reliable system compared to earlier.

Watching this one with interest as I have the same issue. My plan is to take my SC vintage flat track racing so I'm thinking more flywheel weight would be a good thing. How much is too much though? I've seen kits designed for the TY250 from Vape with a 67oz rotor...

I worked with the owner of Powerdynamo (sold to VAPE) several years ago.  Edgar would try to match the "inertia" of the stock flywheel/rotor to one of the several flywheel options VAPE has. 

For example the electric start 125 kit has a heavier flywheel than the kick start only version because the stock 12v generator rotor is heavier than the 6v magneto rotor used on the kick start only models.  You don't need that extra flywheel mass on the 125 and could use the lighter "kick start only" flywheel.

I also mentioned inertia...  it's not just "weight".  Moving the weight out from the center increases the inertia so a 3" OD 2 lb internal rotor flywheel with the mass close to the crankshaft axis is going to have a lot less inertia (inertia can be called "flywheel effect") than a 6" OD 2 lb external rotor flywheel where the weight of the rotor is out farther from the center. 

The distance of the center of mass of the weight is from the axis of the crank makes a huge difference in flywheel effect.

That said, Edgar built me kits for the 125/175 with light, medium, and heavy flywheels...  (Flywheels are "blanks" that get machined for the application) VAPE may be able to build you a kit with a different inertia flywheel than they show for your bike if you ask. 

I'm replying yo Juggler #5--I think. Your SC flywheel is reasonably heavy in original form, but people remove the balancer.  Keep it in there doing its job if possible as adds flywheel innersia through spinning weight & makes it 'smooth' 'as' providing engine mount bolts are tight. Just my thoughts after removing the chain from the one I raced New then refitting it after one motocross. Vibrated terribly buzzy through the bars. Needed an adjustable chain tensioner. Was a Long time ago but things ya never forget.

My buck 20 body could handle it.
Loved the low seat.

Bitch to start.
Pops piston often.

2 year wonder, and an AMA license was needed to buy new.

cliff

I run a DT360 flywheel and ignition system from Rex's Speed Shop. Works great. As I understand it, the DT250 points and flywheel should work too. If they fit the 360 they'll fit the 500.

If you ask akara1 he might be willing to make a bad-ass pipe for that thing.

sc500 had cdi only