NC23 FUEL PUMP

[c7ll]

Hello All,

Does anyone know how a fuel pump on an nc23 (no vacumn pipe) controls the supply of fuel to the carbs?

My bike intermitently floods the carbs but turning off the fuel tap as the bikes running will cure it until the float chambers run dry.

The carbs have been fully re-built, float levels set, and as I say you can do 300 miles or so with no probs and then it starts playing up.

I'm wondering if the fuel pump is at fault and simply supplying too much fuel??

Any ideas fellas?

C

[shadowhawker]

The carb float needle valves are leaking.
Not shutting off the fuel flow when full.

Disassemble the float bowls, clean up inside the needle hole with a cotton but and carb cleaner.
Look at the rubber tips to see if theres a wear line.
Get new float needles from WEMOTO or David Silver Spares.

[c7ll]

I suspected that aswell so I changed all the needles and still the same. The real puzzle is that the problem is Intermitent. I did over a tank of fuel last time before it played up.

I'm thinking the pump is overfuelling perhaps due to a dodgy relay or pump.

Sound possible anyone???

[shadowhawker]

There is nothing in the pump to regulate the pressure, or cut it off when pressure is reached.
Drain the carbs into a container and see if theres any crap in the fuel.May be dust from the tank getting past the filter.
You have put the filter back the right way round?Theres an arrow.

[c7ll]

Sorry I should have said what I've done already:

Flushed fuel tank
New fuel filter
New fuel pipes
New carb diaphrams, float needles and float chambers gaskets
Float levels set
Carbs balanced
Mixture adjusted
New spark plugs

The bike runs great as a result of doing all of the above, but still the intermittent flooding issue from carb 3 or 4

I'm truly stuck!

C

[shadowhawker]

Your float needles are definately not sealing, look at the needle seats inside the carb body.
Have you drained the carbs and checked for crap?It only takes a minute piece of crap.
Get a cotton bud up the orifice!

[selexon]

Your float needles are definately not sealing, look at the needle seats inside the carb body.
Have you drained the carbs and checked for crap?It only takes a minute piece of crap.
Get a cotton bud up the orifice!

I would go with shadow on this one, more then once have I found the carbs on my race bike flooding because of a hair or small flack of dust/grit stuck to the end of the rubber tip of the needle, lucky with a tap on the side of the bowl with a screwdriver can sometimes dislodge the culprit. This is easier said then done on a v-twin compared to the hidden carbs on a I4.

[c7ll]

Slight development on this problem.

Although the intermitent problem is still occuring I have noticed 1 of the 4 carbs has a tiny fuel strainer sitting underneath the the float needle.

I'm guessing this reduces pressure on the fuel flow and could be the reason as to why all 4 needles are not sealing.

When I ordered a new float needle kit from David Silver spares, there's was a slip of paper from Honda explaining the fuel strainer is to be used on a CBR400 but not on other models.

Does anyone have any experience of using these fuel strainers and does anyone know where I could get 3 more of them!?

Cheers all,

C

[shadowhawker]

THE STRAINER, IF CLEAR IS NOT YOUR PROBLEM, DONT GET SAIDETRACKED, GET THE FLOAT NEEDLES CLEANED

[shadowhawker]

AS BEFORE...CLEAN THE FLOAT NEEDLE SEATS WITH A COTTON BUD AND CLEANER, DONT WASTE MONEY
DON