Monty Allen Keyed Cylinder Bolts.

[mx250]

A little time ago someone was asking about them, even discussing how to manufacture them. This might save you the trouble....

http://cgi.ebay.co.uk/MONTESA-COTA-AND-CAPPRA-CYLINDER-HEAD-ALLEN-KEY-NUT_W0QQitemZ330267638068QQihZ014QQcategoryZ122304QQcmdZViewItemQQ_trksidZp1713.m153.l1262

Says there's 10 available at about $10A each  (thank god I've got a few spare )

[Lozza]

I found a plentiful supply of these nuts much cheaper than these.

[montynut]

Well go on tells us!!!!

[cappra]

Yes, please do! 

[Lozza]

They need a quick skim on the lathe to ge the OD down a bit. They cost $3AUD each, if you want I'll do a run of them,which will bring the unit price down. ???I could just say go down to the local kart shop and look at the wheel nuts but that would be to easy and deprive me of some fun.