MOPED ARMY

Unless you are turning more than 9k then the stock crank can take it. That full circle crank has RH threads on the magneto side, so you also need a right hand M11 nut for the flywheel. The difference in primary will not make a noticeable difference on a full circle crank.

In my opinion, always on a build (stock crank or full circle) you need to open the mouth of the oil journal with a drill bit so it is funnel shape. That will feed more residual oil to the mains where it is needed. Best practice is to change the spi seals as Graham mentioned.

Also match port the transfer lead ins and index your cylinder to get the best bang for the buck, whether you are staying completely stock, porting or kitting.

the balance factor should be close, its just how they achieved the weight reduction and the manufacturing method.

i have seen 2 airsal kitted (slap on kit job) big end bearings go out at well under 9k rpm so i'm leery of them.

oh yeah one other thing i forgot to mention- because of the stock airfilter on AV7's and them being piston port, they like to accumulate water in the bottom end. If they are left outside, or even sometimes if they are shedded... maybe something with condensation, i dunno. Either way i've worked on a lot of AV7's with rusty bottom ends, way more than other types of bikes.

I think in both of those failures mentioned above, there was corrosion in the needle bearing that caused them to fail early. Nothing you could feel, mind you. I was just thinking about it and forgot about that factor. So something to be wary of.

yeah its bizarre. my brother had a hobbit that got left in a damp garage a few yars ago that the crank turned into a solid rusty mass, but nothing else was affected at all .... super odd. usually with the two stroke oil coating things, even setting up, engines tend to stay pretty clean.

i dunno if its more or less common with a dellorto on a shorty intake vs. the stock bendy has anything to do with it? Maybe something with the exhaust? who knows.

Rusty cranks and rusty gudgeon pins happen a lot. If you store a bike in a unheated building best to cocoon the bike in plastic and tape it up goodly. Throw a bag of kitty litter (Pestel beads is best but any clay litter will do as second choice) sliced open onto the floor of the cocoon before you close it up and tape the heck out of it. The litter will wick up any moisture in the plastic bag of bike.