yes there is!

1. the old ones- unpolished - have an advanced timing mechanism that is attached by 2 rods to the carb TH and to the pickup sensor mobile Teflon ring , this way the sensor !QUOT!moves!QUOT! as the TH does respectively.

2. the new ones- polished - have a fix-point sensor and an additional elec unit in between the sensor wire to the ignition unit.

brison are great engines, just be aware tht brison have changed owner lately, and some users here have complained about start-up troubleshooting after 30min of work...?

my suggestion, double check your self and the product you getting....( good for other things in life )