vacuum on sr250

[spooky]

just got a 1981 yamaha sr250, the pipe from petrol tap to carb manifold is pulled off and blanked, would this cause a lack of power ? i know they are not fast but this one is dreadfully slow, air filter ok, plug a nice colour, haven`t checked timing yet but it starts and runs ok, 

[johnr]

id b surprised if it ran at all. the vacuum pipe opens the tap, if its not connected that in theory, the fuel tap shouldnt flow anything. unless its on prime. have you tried taking the pipe off the tap and seeing if anything comes out. also, is the vacuum take off on the carb also blanked off, becaus if its not, it could make the bike very sluggish at low engine speeds and affect pickup.

[spooky]

i reconnected the pipe from tap to manifold,   { it was running on prime  as you suggested } it has improved slightly, i found the carb to air filter rubber was poorly fitted as well, but i will try another run tomorrow and see if it has improved,  thanks

[iansoady]

I hate those vacuum operated taps and converted the one I had on a Honda 4 to work conventionally.