Motorcycle Repair: 91 FXRS POOR RUNNING, rear pulley, belt pulley

Question
QUESTION: Hi,I run a 91 fxrs-c with se11 cam dyno-jet carb kuryakyn filter vance&hines short shots and have just replaced the rear pulley and belt with which I was assured were the oem parts for my bike the belt is 130 th so had to get a 70 th pulley,I'm now assuming the origional belt/pulley was 65 th 120 oddbelt similar to sportsters,(its a european model) no big problem but the bike sure is fast off the blocks but runs out of steam around 80mph,was told this set up should be good for 100,have replaced the carb diaphramme but no difference.Any idea's.Thanks

ANSWER: At 80 MPH what RPMs are you running?
Mike

---------- FOLLOW-UP ----------

QUESTION: Around the 4,500 mark dont like running it up there because it really feels strained, after replacing the belt with what  I was sold as oem kit then having to get a 70 th pulley i've "lost" 500 rpm e.g 70mph was 3000 rpm,now 7500,before with the origional belt/pulley over the 100mph was possible,i've also added a v-thunder ignition unit set as per their instructions although the bike ran like this before I swopped the ignition.I keep thinking exhaust but this stuff should run well together from what i've found.Cheers

Answer
When you changed your belt and pulley, you changed your final drive ratio. Now you need more RPMs to get higher speeds, but you will be faster out of the hole. About the only thing you can do is go back to the orgional setup.
Good luck and happy riding
Mike