Any HPI ignition experts out there? I have just fitted a HPI ignition imported from Belgium. It’s a great piece of gear. Starts my old ‘73 SC500 in 2-3 kicks when cold. The instructions supplied stated the timing for the all single 2 strokes is 2mm BTDC. I have done this and the bike starts and run fine, no kickback!! 
Should I re adjust the timing to 2.7 mm BTDC as stated in the Yamaha service manual or just leave it at 2mm?

Do you think it digitally alters the timing while running or stays fixed. I guess strobing it would prove that. Not sure what i'd do but maybe they've decided 2mm is kinder to the motor than nearer 3mm. They did like to seize if things weren't right or leaned off too much. Have you used it in anger or just in the shed. If not & you know how it used to run on the track i think i'd go & give it a whirl as is before altering. Have mixed memories of the SC. Was just the best on a fast grassy relatively smooth circuit but too much for me in the rough. Ya lucky to have one.

The HPI has an auto retard of about 5-6 degrees at around 6-7k rpm. You should be fine, but do an in depth plug check.I  run it at 1.9 with a built-up 250 motor

2mm is probably the safest bet. You can always try 2.7 if you keep an ear open for detonation.

That's one perk about the 500. You don't have to wring every ounce of power out of it. Jet it a little rich, leave a few degrees of advance on the table and it still should make enough power to scare you.

Thanks for that guys. I will leave it where it is at 2mm.