My 2 cents-
I don't believe the issue is with the rad fan. If anything, a partially blocked rad or possibly the coolant system needs burping which has been a long standing issue.
I did a mod for shits and giggles using a ran fan from a ZRX1200 which happens to be a 7 blade version of our 4 blade fan. Testing revealed an increase of airflow of about 30%. Did I need to do it- probably not but me being me I chose to exercise my abilities and do the mod.
Here's a listing for a
zrx 1200 rad fan on EBay
and a link to my fan shroud mod
starting at post #7951 and follow through for the next 2 pages for the final result
what temps are you riding in? its been over 100 degrees like the last 2 weeks here, i tried burping my system forever to make sure it was working good, maybe it does need a good cleaning, but my voyager typically runs 1 to 2 bars past the center, and i'll usually see it go to 3 bars past a few times during riding but its usually not there very long. I'd like it to run cooler, but part of me thinks its the crazy heat and it wont do better till things cool off