Fueling problem CB350

[twinsorin]

I'm stumped. '72 CB350. Got it from a friend last year. Rode it as it. This spring rebuilt the carbs, soaked, cleaned, small orfices in jets and such cleaned with thin wire, blew out all the passages with air. I also put two lawn mower filters in line from the petcock.

Bike would run great until we got on a stretch of long uninterrupted throttle. The carbs would drain the fuel line (see through filters at bowl level). After it sat for a couple of minutes the filters would fill again and it would fire up and ride for awhile before it repeated in the same way. I could see through the clear filters that there was just a tiny trickle coming into them. So I changed filters to a larger automobile type, with replaceable elements and I put on a new stock type petcock (needed one anyway). It's better. However it still drains the lines and sputters on long throttle runs above 50 or so. Let it sit and eventually it fills the lines and runs fine, until...

I've made sure the bowl vents were clear. Any ideas as to what the problem might be?

Thanks, David

 

[xb33bsa]

if you disconnect the fuel line from the carb and hold it in a similar position as when connected ,do you get a nice steady stream with the tap open ?
what kind of fuel line routing ? got a pic of that ?
are the vents to the bowels clear of obstructions ?

haha bowls not bowwels

 

[twinsorin]

if you disconnect the fuel line from the carb and hold it in a similar position as when connected ,do you get a nice steady stream with the tap open ?
Yes.

what kind of fuel line routing ? got a pic of that ?
Routing runs from petcock to filter then loops under the carbs to the fuel connection on carb. No picture, but could later.

are the vents to the bowels clear of obstructions ?
I blew them out when I cleaned the carbs and have since blown through the vent lines to see if they were clear. I could hear the air in the carb bowl.


haha bowls not bowwels
Bowel maybe right, irritable bowels!

 

[xb33bsa]

i never have liked the idea of routing a fuel line down all the way under the carb and back up try short lines without filters, your petcock has a screen

 

[twinsorin]

I'll drop the filters and see what happens.
Thanks,
David

 

[xb33bsa]

elimination process, that one is easy to do
good luck

 

[TheCoffeeGuy]

Also check the gas cap vent. When the bike starves off, watch your line and open the gas cap. If you get a sudden flow of fuel, problem solved, clean out the vent.