Help a newbie please

[fastbikefinder]

Hello,

I recently purchased an NC30 that has been stored in a barn for years.

she's a nice old girl, with 27,000 kilometres showing, but the 7 year storage has had a toll on the carbs.

I've rebuilt many carbs over the years and I'm not shy of pulling them apart, but I've had a fuel starvation problem which is getting a bit tedious now.

If I thrash the *(&%^ out of the bike alls fine, but as soon as I get back to 30-40mph limits areas where poodling is needed she runs out of petrol.

The vaccuum hose is in good condition, and the diaphrams appear to be in very good condition aswell, I'm susprised at how thick they are.

On first examination of the carbs 2 of the needle jets were completley blocked,and had to be honed out, but the rest were just dirty, but generally in very good condition, floats etc.
I've given the carbs a good soak for almost a week as I suspected some of the airways were blocked.

Imagine when you remove your fuel tank, start the engine and put your finger over the fuel inlet pipe, you usually get a sucking on your finger while the carb is trying to pull the fuel through...well, there is no sucking with these carbs.

As a process of elimination I have done the HRC mod to the fuel tap just incase there was a problem with the tap diaphram also, but this hasn't made a difference either.

The inlet carb rubbers are also in good condition, and I easily get the carbs reseated every time so I'm 100% confident that the carbs are properly sealed to the heads.

Has anyone here had this problem at all, as I said while there is fuel in the carbs she runs lovley, take her out and thrash ten bells out of her and alls tickety boo, then come back down to slow speeds and within a few miles she runs out of petrol.

By the way, I've checked the routing of the tank breather hose, it's not crushed or blocked, and the breather valve in the tank is also working fine.

Any help would be appreciated,

I'm just hoping there isn't a valve issue, but there appears to be good compression and she fires/runs on all four too.


1 thing I also wanted to check is that the breather from the tank should come through and down to the side stand area, but where does the other piece from the T junction supposed to go?


Thanks

[Neosophist]

Your floats arn't sticking are they? (And have you checked the float heights?)

How do you get it started again if it 'runs out of fuel'?

[fastbikefinder]

Hi,

The floats are lovely, and work very well.

I have to blow through the fuel tank breather to force fuel into the fuel lines and I'm off again, fine whilst thrashing it but run out again when back down at low speeds.

[fastdruid]

Did you pull the float valve seats out?

My VFR750 has individual filters on each one and the fine rust from the tank (from it sitting ~3 years before I got it) blocked them.

I took a look at the '89 VFR400 fiche I have and it looks like it also has what looks to be filters on each, don't know if all the models are the same though.

Druid

[Neosophist]

Yeah.. thats the kinda notion I was going towards.

When you cleaned the carbs did you use compressed air to blow through all the holes, carb cleaner wont' disolve any rust / dirt particles.

Sounds like you have a blockage...

One suggestion would be to attach lenths of clear plastic tube to the carb bowl drain nipples and when it dies open the drain screws on all the carbs see if any of them have any petrol in.

[fastbikefinder]

Yes, completley stripped each carb, pulling everything out, the filters were complotley clean and each of the holes in the body were open too.

Did you pull the float valve seats out?

My VFR750 has individual filters on each one and the fine rust from the tank (from it sitting ~3 years before I got it) blocked them.

I took a look at the '89 VFR400 fiche I have and it looks like it also has what looks to be filters on each, don't know if all the models are the same though.

Druid

[fastbikefinder]

Yeah.. thats the kinda notion I was going towards.

When you cleaned the carbs did you use compressed air to blow through all the holes, carb cleaner wont' disolve any rust / dirt particles.

Sounds like you have a blockage...

One suggestion would be to attach lenths of clear plastic tube to the carb bowl drain nipples and when it dies open the drain screws on all the carbs see if any of them have any petrol in.

That's a good idea to try, it'll help confirm, but then again because it's running out of fuel when at low speeds, I think they'll be empty

[shokrabi]

you put the vacuum hose on the rite way on the fuel tap side?