fuel line routing on cb 750

motorbikejesus

motorbikejesus

Burnout?? Burnout!!!!!!!!!
hey eveyone, my 74 honda cb750 is almost done, took her out for a ride today and was only running on two cylinders, so i come to find im not gettin fuel to the carbs farthest away from the petcock. , is there a certin way the fuel lines need to be run?, i got a new pectcock so im sure its not that, , i ran the line on top of the intake boots to the carb, but it aint flowing fuel.

How did you guys run your fuel lines? im thinkin maybe hard lines? thanks
 
Have you got a pic of the fuel tap? I'm thinking it might be a vaccum tap and the 2nd outlet might be for the vaccum line (??)
 
is it a stock cb750 petcock?

I think there should be two outputs, one for the left 2 carbs and one for the right 2, aren't there two little nipples on the tubes that run between the carbs?
 
yes there are those to nipples in between the carbs. what r they for, and theres 2 taps on the petcock, but none for a vacuum line.
 
motorbikejesus said:
yes there are those to nipples in between the carbs. what r they for, and theres 2 taps on the petcock, but none for a vacuum line.
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the 2 extra nipples on the carbs are a vent, they go nowhere. do not plug them or run'em to the tank. the 2 ports on the tank are for 2 fuel lines as stated before. 1 line for each set of carbs. the carbs are gravity fed, no vaccum needed. the gas cap is the vent on a stock cb750.

my guess is the petcock is the problem. lean the bike side to side, the fuel should follow. if not pull the petcock and make sure the screen and all holes are clear. unscrew the cover from the lever and make sure theres nothing blocking the ports.
if only one line is getting fuel, swap lines and see if it works on that line. hell you might just have the line to much of a curve, restricting flow.
 
ok thanks i found the problem, i thought those nipples hehe between the carbs were vacuum so i had a vacuum line between them , ill take it off when i get home , thanks everyone
 
hey sry i took the vacuum line off but my tank is away getting painted, so i cant run it, but im pretty sure thats the problem im just gonna run the lines under the carbs. when i get the tank back, ill let you know if it works , thanks again
 
Old blisters like yours are usually coated with tank rust,,,or maybe not!,,inline fuel filter(s) might be a good idea for the street ....tuck away some extra's in your tool kit
 
oh no i completely treated the tank its super clean , still at the paint shop :(, hopefully i get it back soon, its gettin real cold here in illinois
 
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