OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions on Other Engines Flywheel bolt size

Can anyone tell me the bolt size and thread size for the Flywheel bolt that holds
the starter pulley on a Villiers Mk12

Someone on this forum is sure to know, and this information was occasionally included in the manuals.

I have run into similar problems myself. What you can do is try to measure across the thread diameter with an imperial ruler or gauge. This should at least tell you if it is 3/4" or 1/2" or whatever. You will find most of the old shaft threads are either UNC (coarse) or UNF (fine) - but I'm sure there will be exceptions. You may also need to count the number of threads to an inch. Some shafts have specific thread counts (TPI).

If you get stuck, you could try taking the whole thing to an engineering works or a nut and bolt specialist. They should be able to tell you the exact type of thread and size. Good luck!

Hi thanks for the feed back
I think it's 9/16 TPI 20 UNF thread ?

As it's a Villiers, it's quite likely that it uses Brit standard BSF/BSW threads, not US [i.e. UNF/UNC].

The standard pitch for 9/16" BSF is 16 tpi. An Imperial screw pitch gauge is the best tool to use, to check this.

I wonder if they used a Villiers thread on this, Enfield were still using a Villiers thread on the rotor nut on their bikes until 2008. Villiers being so big back in their heyday, just created their own thread sizes

Hmm a bit confusing might try bsw 9/16 20tpi tap if I can fined one