Ace, what general up grades ( if any) do you recommend for lower end of the AVL with Fire Ball?
Well, it depends on how well the factory did with each particular bike. In theory, the AVL supposedly has all the necessary upgrades already in it. It has the roller bearing on the big end of a steel con rod, and high output oil pumps, and an alloy barrel as standard equipment. Where the questions arise with the AVL, are whether they put it all together well enough to ensure that it will hold up.
If you would like to know what I think might be the places where stress failures might occur on a higher output AVL, I think it would be in the bearings. The bearings are the same as the Iron Barrel engine, which would be okay if they were very high quality units like we put in with rhe Fireball. I think it's pretty clear that the factory opts for bearings that are quite a bit lower in cost, and so they often don't take any added stress very well. With the AVL roller big end bearing, it's just like the UCE. Depending whether they got the hardening correct on the big end eye of the con rod, it might hold up fine if it also got the proper clearance during assembly. If it didn't get good heat treating and proper clearance, then it won't. We can't say what will happen because of variance in manufacturing.
For an AVL owner looking g to upgrade and do things to try to overcome these potential issues, I would say to get a good set of bearings like we use, and get an outer race installed in the con rod which is precision honed to proper clearance for a new top quality roller bearing like an Alpha bearing. Rebuild the crank with precise truing to minimize vibration.
These are the things we do with the Fireball. With an iron barrel bike, it's obviously needed to change all the bottom end parts out before trying to upgrade the power. With the AVL, it is less obvious, and it may, or may not, be necessary for a mild/moderate power increase. For a big power increase, I would go ahead and do a full upgrade to the bottom end in advance.
With the behavior of bearings in failure mode, they give plenty of warning with knocks and other bad sounds when the begin failing. So it is conceivably okay to try the power mods on the stock bottom end, and if it holds up to it, then fine. If it starts knocking after maybe 1500 miles, then it wasn't okay, and you need to open it up and do the bottom end work to it. Otherwise, it could all be done at first as a preventive measure. We have no way of knowing which engines will be able to handle the power upgrades the best. It was determined at the time of the bike's manufacture. Lower power upgrades are more likely to do okay without bottom end mods than big power upgrades would be. If you do the bottom end work first, then it will handle any power upgrade level that you might want to choose.
These choices are made by each owner. The above info can be a guideline. I can't say for certain what engine can withstand what level of power in factory form. It is very much a "luck of the draw" situation of how well the factory did on your specific machine.