You might try calling Ralph Cunningham at RC Ignitions / 1783 Whitehall / Williams, AZ. 928-220-5721

Without doubt, he is the Zenoah expert! He keeps trying to retire but I believe he still services some engines. Call him and discuss your problem, you won't be disappointed. I'm not sure whether the phone # is current but if not, someone will probably chime in with a correction. He likes to be called the Grumpy Old Man but he is a treasure of engine knowledge! Treat him right and he will do the same for you.

If you want to replace the ignition system, Milton at RC Extreme Power sells the RCExl ignition kit for the GT-80 which is a bolt on replacement for the original mag system. Here is a link

http://www.rcextremepower.net/

Good luck!