RE: Saito 4 Stroke Glow plug threads.
You have to send the jug to a guy in California by the name of Clarence Lee. Its about $13. Find his address with the search function.
The threads are 1/4"-32. The 32 threads per inch is what causes the problem. US coarse threads are 1/4-20 and the fine standard is 1/4-28.
Enjoy,
Jim