I have an '03 drifter 1500. I have noticed that when I am in fourth or fifth gear and speed is 65 MPH or above if I add throttle there is increased RPM but VERY slow increase in speed. All seems normal through the gears from 1 to 5 at lower speeds. Could this be the WEAK clutch springs I have read about? Has any one experienced this and what was your solution?
First, have you changed your oil recently? If so what did you use? If not, you may have a spring issue.
Here's a link to my thread on when I did my spring: http://www.vulcandrifterriders.com/forum/index.php?topic=324.msg1267#msg1267
There's more here: http://www.vulcandrifterriders.com/forum/index.php?topic=1170.0
Mine was doing the exact thing - at only 20,000 miles- bad clutch spring. the Vulcan 1500 clutch curse. It seems highly likely yours is the same problem, from what I've read. We both had the textbook symptoms. How many miles on your bike?
There is tons of stuff on this forum. Here are some more I had bookmarked that I studied while deciding what to do with mine.
http://www.vulcandrifterriders.com/forum/index.php?topic=1170.msg56865#msg56865 (http://www.vulcandrifterriders.com/forum/index.php?topic=1170.msg56865#msg56865)
http://www.vulcandrifterriders.com/clutchparts.html (http://www.vulcandrifterriders.com/clutchparts.html)
http://www.vulcandrifterriders.com/forum/index.php?topic=566.msg3813#msg3813 (http://www.vulcandrifterriders.com/forum/index.php?topic=566.msg3813#msg3813)
http://www.vulcandrifterriders.com/forum/index.php?topic=324.0 (http://www.vulcandrifterriders.com/forum/index.php?topic=324.0)
http://www.vulcandrifterriders.com/forum/index.php?topic=17460.msg29807#msg29807 (http://www.vulcandrifterriders.com/forum/index.php?topic=17460.msg29807#msg29807)
http://www.vulcandrifterriders.com/clutchspringreplacement.html (http://www.gadgetjq.com/clutch_spring_replacement.htm)
I opted to do the mean streak spring, with the judge washers - it was a lot cheaper than the new/improved Kawi system.
My spring was in terrible condition - the fingers were worn down to almost razor sharpness. It wasn't a terrible bad job - I spent longer on several of my "minor" custom mods I made- they always take longer than the routine maintenance stuff!!