Gregory Bender

Ring gear/slip ring information

Moto Guzzi V700, V7 Special, Ambassador, 850 GT, 850 GT California, Eldorado, and 850 California Police models



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Roy Smith contacted me inquiring about how to properly time his 850 T3, which lacked the correct timing marks on his flywheel. I made some measurements of the starter ring gear and performed a few calculations. The resulting data is presented below and would apply to pretty much all 8-spring flywheel ring gears fit to Moto Guzzi big twins between 1967 and 2007 (MG# 12067900, MG# 17067900, MG# 30067925).

The circumference of the ring gear is 759 mm (I measured twice). The number of teeth on the ring gear is 96 (I counted thrice). So, one tooth on the ring gear is equal to 7.90625 mm in circumference. One degree is circumference is equal to 2.1083 mm. Therefore, one tooth on the ring gear is equal to ~3.75° of circumference. If full advance is 33°, then that would equal 8.8 teeth.