Topic: Carbs are not getting any fuel after rebuild

[leesfer]

Trying to start my bike after a complete rebuild, it has spark but only carb #1 is filling up with fuel, the #2 is okay, #3 and #4 are completely dry after kicking it at least a thousand times

Any ideas?

[harisuluv]

What bike?

You don't need to kick it over to fill the bowls.  You should be able to turn on the gas and they should fill.

Don't know what bike it is but check your fuel ine routing

Tap the bowls with a screwdriver handle to unstick a float if need be.

[tomkimberly]

Speaking from experience, did you install the floats upside down?   

Tom

[disco]

Hi Leesfer, this might seem obvious but........ you have got a tee in the fuel line so that it splits into two lines & you're feeding the 1&2 carbs then also the 3&4 carbs?

[leesfer]

The bike is a '75 CB750

I have the fuel routing set up like this, is this correct?



I double checked the floats and they are on correctly

[iron_worker]

So no fuel is getting to the bowls? Or do you mean the spark plugs are dry?

There is only so many things that could stop fuel from getting to the bowls.

1) Tank - is it rusty and plugging up your petcock
2) Is your petcock full of junk as above
3) Fuel lines ... are they in good shape? Are they pinched off? Do they flow downwards towards the carbs or do they have a high spot in them that traps air?
4) Float/needle ... are your floats in correctly? Do they move freely? Are you needle/seats in good shape? Are they seized?
5) Carb vent lines ... are they plugged? If so, they can create pressure preventing the bowls from filling completely.

As was said ...the fuel bowls should fill up as soon as you turn the petcock on. It should have nothing to do with kicking it over. Kicking the bike over simply creates
a low pressure zone in the carb throat that draws the fuel up from the bowls into the intake runners and thus the cylinders.

IW

[leesfer]

The carb bowls are completely dry

I'm not using a tank, just a straight line coming from a gas container going into the carbs. The fuel line is vertical with no air traps

The carb vents are clear

I've rebuilt the carbs so everything was soaking and cleaned before reassembly but perhaps I did something wrong here? This was my first time rebuilding carbs so I am guessing I messed it up

[leesfer]

I guess I will just have to remove my carbs again and go through them to make sure there is no blockage

[lucky]

Trying to start my bike after a complete rebuild, it has spark but only carb #1 is filling up with fuel, the #2 is okay, #3 and #4 are completely dry after kicking it at least a thousand times

Any ideas?

Kicking the engine will not make fuel flow into the float bowl.
If you kicked it a thousand times you could have damages something in your leg or bike.

I think you better get a mechanic to look at your bike.

[Xnavylfr]

Before you remove the carbs from bike try just removing the bowls..Turn on your gas and see if you get FREE flow out ALL carbs!!  Look to see if the needles drop with the floats if you don't get gas flow.  SOMETIMES  you can remove the float pins and floats  and look at the needles.



Xnavylfr(CHUCK)

[harisuluv]

Ok the drawing is good and all but how bout some pictures of your carbs..

[leesfer]

Kicking the engine will not make fuel flow into the float bowl.
If you kicked it a thousand times you could have damages something in your leg or bike.

I was under the impression that the vacuum was just as much a reason as gravity was in terms of pulling fuel into the carb

[leesfer]

Ok the drawing is good and all but how bout some pictures of your carbs..

[motosan]

Before you remove the carbs from bike try just removing the bowls..Turn on your gas and see if you get FREE flow out ALL carbs!!  Look to see if the needles drop with the floats if you don't get gas flow.  SOMETIMES  you can remove the float pins and floats  and look at the needles.



Xnavylfr(CHUCK)

+1 on that!

[disco]

OK, so you're getting fuel into carb 1 & (maybe) 2?
Why not disconnect the fuel tube from the inlet to carbs 3 & 4 and confirm that fuel is making it to that point? If fuel is flowing from the tube there then that kind of narrows it down to the needle & seat of 3 & 4.

[leesfer]

OK, so you're getting fuel into carb 1 & (maybe) 2?
Why not disconnect the fuel tube from the inlet to carbs 3 & 4 and confirm that fuel is making it to that point? If fuel is flowing from the tube there then that kind of narrows it down to the needle & seat of 3 & 4.

I'll be taking them off tonight when I get home hopefully so I can easily check if it's flowing. It'll be much easier to troubleshoot from my bench

[mrrch]

You mentioned vacuum so I have to ask where is the fuel line coming out of your temporary fuel supply?

[leesfer]

You mentioned vacuum so I have to ask where is the fuel line coming out of your temporary fuel supply?

It's being gravity fed from a funnel directly above the carbs

[leesfer]

Took the carbs off last night and checked everything.

The fuel line going to carbs #3 and #4 was clogged full of rust. I cut new lines and checked the flow with the bowls and floats off. Everything flowed nicely. Put all the floats back in and a couple carbs were not flowing so I guess it's just down to adjusting the floats now.

[tomkimberly]

You need to elimate the source of the rust otherwise you will continue to have the same problem, over and over again.


Tom

[harisuluv]

Adjusting the floats is only going to adjust when they stop fuel flow. If they aren't flowing or getting gas something is wrong again. If you have enough rust in your tank to actually clog the whole fuel line then you have bigger problems than float adjustment.

Even if you were to keep the lines free your float valves would be so contaminated with rust particles or debris that you would have constant overflow leaking.

You need a thorough cleaning out of all the rust in the carb body circuits.

Of course as Tom mentioned you need to tackle the rust problem in your tank first.  Sounds bad.