I was a harley dealer mechanic straight out of aviation mtx school for a few years. Id recommend against an iron head sporty unless you want it as a "bar hopper" around town bike. these are 4 speed bikes, and no good for running at freeway speeds for any distance. A buddy of mine has a 1971 XLCH sporty. He ran it to Sturgis one year, it damn near shook itself apart. I welded up the broken tabs on the chain guard, and a bunch of other stuff fatigued and failed. You cannot convert a 4 speed sportster to a 5 speed like you can w big twin machines. The sportster transmission is unitized with the crankcase. Big twins you can change out a 4 speed trans for a 5 or even 6 speed with the right adaptors to mate it to the frame and primary chain case.
If its gotta be a sportster, I would definitely recommend an evo block head sporty with 5 speed and belt final drive. Gets the RPMs and vibration down to an acceptable level at 70mph, and the belt drive is mtx free for up to 50k, though i have seen full dressers get 100k out of a belt drive. Only thing that destroys one in short order is a rock getting caught in one.
Sportys also have an issue with oil pump failure at constant high RPM. Rrmember its a dry sump system and the pump does 2 things, provides oil pressure on the feed side, and crank case scavenging on the other side to pump oil back to the oil tank.
Sportsters have a 2.25 gallon tank. Get a larger 3.0 gallon peanut tank , or an aftermarket sporty fstbob style tank. Its doubtful you would want to be on it for more than 3 gallons of fuel before you stop, and stretch your legs anyways.
Hope this helps
Matt
