No timing light needed, they all have timing marks. If it won't run with the factory ignition timing then i would check the cam timing to make sure its not out, skipped cam chain, someone put it together wrong, etc. For example on a 200 series motor you set the crank to the T mark for TDC, then check the cam gear timing to make sure its dot is lined up with the notch/line on the rocker cover, then to set ignition timing you set the crank to the F mark for Fire, then you just adjust the pulse gen to match the line on the advancer at whatever position it ends up. That generally puts you around the middle of travel on the pulse gen mounting plate slots. If it won't run in that position then something is wrong. From there you could advance or retard it a bit, but i have never had to do that to make them run right, just setting the factory timing does the job.
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1984 Honda ATC200ES "Big Red"
1982 ATC200E "Hondie"
1988 TRX300FW "Project Quad" Still in progress....