Thunder Tiger is one of the worst outfits to get parts from other than Norvell. The engines are great but their marketing policies stink. They normally do not talk to individual consumers. Their attitude is that you should go back to your dealer where you purchsed your engine to get the parts.
What dealer??? If you can find one, they are very helpful. But you didn't purchase the engine from a dealer.
Try this guy, he is a dealer and has been most helpful to people on RC Universe. This is his web site but it is not interactive. Get the phone number and call him or use his Email address.
http://www.paulsmodelsupply.com/
Enjoy,
Jim