When working on an Iron head sportster.  

You can add a 24020-51 left-hand thread screw to pinion shaft,
drill a n50 hole in screw center, before installing it.
This will meter the oil flow at any rpm range.
It will add more oil to the top end for cooling and lubrication.
Add late model 24633-77 vent value to engine. this is a one-way
value it will help make more power and run great.
Install a 1 ¾ ex value for more rpm and power, bore out ex port
in head for ex value flow. Kibblewhite black value are the best.
Tulip shaped value head will have up to 20% more flow.
Value coating with help stop Stem galling and deposit build up.
Put seals on all kinds of guides.
When using soft cast iron guides and bronze guide, if they get worn.
You can always knurl i.d. and rim to necessary size for clearance.
Remove rocker arms shaft spring, make up and install a spacer
like in the shove head rocker boxes. Set up end play at .020
Check ex rocker arm stem and spring oiling hole, you have to drill
through rocker arm and bushing for positive oiling. A lot of oil hole
is blocked, by the bushing. Rocker arm with oil hole is only for ex.
Crane spring kit offers more seat pressure then stock spring set.
Kit .500 & .650 is good investment.
Spring coil bind clearance needs to be .100 more then cam lift
specs.
Remove bottom collar, use spring head shim.
Use Crane spring pocket cutters.
Need minimum of ½" from top of guide to bottom of keeper groove.
Install left front bottom motor mount oil filter system and any
oil cooler.
4-thing oil is design to do.
1.Lubricate parts.
2.Cushion parts.
3.Clean parts.
4.Cool parts.
The cleaner and cooler you can make the oil the better it will
work for you. Filter oil first and then cool it.
Install a HI-4 crane ignition, a voes switch and duel 3 ohms coil,
set on single fire.6k rpms 4 slope.