RE: Stiletto from Corvidae.net
Hi J0rrit,
I believe the newer 3.5cc AXE Rossi's and Novarossi's have a 1/4"x28 threaded crankshaft, while the older 3.5cc Rossi's have
a 6mm x 1.0mm thread (M6). Even though 6.15mm seems too small a diameter to be 1/4" (1/4" = 6.35 mm), you may have
1/4"x28. The '28' is the number of threads per inch. A 1/4"x28 has a finer pitch thread than 6mmx1mm. The 28 threads per
inch corresponds to a pitch of 0.907 mm, which you can check with a caliper, or even check it is finer by just holding your
crankshaft against a known M6 screw. I can't believe Rossi would put a unique exotic thread on their crankshaft, it is almost
surely 1/4"x28. TruTurn also makes adapters for 1/4"x28 and a matching turned bushing for the spinner backplate is included
in the adapter kits, so there should be no need to customize an adapter yourself. 1/4x28 is very common here in the USA for
most engines from .21 cu. in. (3.5cc) through .50 cu. in. (8.3cc), and the adapters are also easy to get. If you have real trouble
to get them in Belgium, send me a PM; the adapters are small enough to put in a padded envelope and send with regular mail.
Just check / verify if the pitch of the crankshaft thread is indeed 0.907 mm, then you will know what thread adapter you need
for sure. Also measure the crankshaft diameter, as some engines have a larger diameter crankshaft stud at the drive washer
that then "steps down" to the thread size. TruTurn makes the right bushing for your engine too!