Lurching at high speeds

[jakedkat]

My 96 Katana runs great and runs strong all the time except for when i get on the freeway and drive a while, it goes and then falls back and then lurches forward and then slows down over and over again. DOnt know if any other Kat Riders have had the same problem with their babies, dont know. MY first guess was fuel, thats what it feels like.

[md86]

Sounds like "surging" , which could mean either .....
a) lean . But they don't usually seem to do that stock , eh ? Or
b) something's MAKING it run lean ......

[Wade-Kat600]

Actually i'm going to go with fuel flow to the carbs - sounds like the bowls are emptying out faster than the fuel gets in - when it starts to cut out (the power loss he's describing) fuel consuption reduces and allows the bowls to get a little fuel in em - then it kicks back in and fuel consumption returns to a higher rate than the fuel is flowing.

Thats why it runs fine at low speed but not high speed over a distance. Running around town doesnt maintain the high fuel consumption like freeway miles do.

Fixes - first - determine if it is the tank valve, fuel filter, or in the carbs themselves.

Next - fix whichever one of those it is - if it is the carbs you're looking at a very throrough cleaning at a minimum - likely a float adjustment as well

The fuel valve could be the vacuum return - I would say you could test this by setting it to the prime position which overrides the return line. Then go for a ride. If it runs fine at freeway speeds then you need to trace the hoses and figure out what either isnt connected or what is clogged.

[Black_peter]

You could also check the tank.. If it isn't venting right you could starve for fuel.