Nc30 Emulsion Tubes: Where To Buy Them

[lorenzo]

My little NC's quite boggy in the middle, It's something I mentioned some time back, and despite making sure the floats are spot on etc, it's steadily getting worse, the flat spot is now as wide as 6-9k more or less, and I've come to the conclusion, based on nothing more than riding it, that the dynojet needles have done the classic wearing the emulsion tubes trick. So, where's a good place to get some fresh tubes from?

[Beanerno1]

Try rick first +44(0)1603 720387

Then probably david silvers parts

http://www.davidsilverspares.co.uk/

[lorenzo]

Forgot to mention, it's a UK model, and I think the carbs are a little different on these in comparison to imports, is that right?

[marcaztls]

What year is it Loz?

[banoffee]

I'd ask Rick Oliver first as a starting point.

[lorenzo]

What year is it Loz?

2013.

Next question?

The bike's a '92 i think, K reg, whatever that is. It's pretty stock other than an end can. The jetting when wide open is bob on, likewise from idle to about 6k, then it gets really wooly. I was giving it some stick last night coming home (got to get the harder riding in while you can this time of year), and let the revs drop to about 7 while I went round a big sweeping slip road, dinked it down as I exited and the bloody think back fired, there was that much excess fuel knocking about. That can't be good, can it.

[marcaztls]

Yeah yeah, I did walk into that...

Well sadly Honda UK have discontinued the emulsion tubes, so Rick Oliver or David Silver is going to be the place.

BUT, looking at the fiche, emulsion tubes on these carbs aren't touched by the needles as they're in a different plane to the needles. My stupid memory can't remember these carbs directly, but are you sure they're not ones where the part that's worn can't be replaced?

I hope I'm wrong and talking out of my arse...

[lorenzo]

You may be right, I've not even had a look at them, I've just jumped to that conclusion. I suppose I should have a look at them and also just ask the general question: What would cause an NC30 to run rich in the middle 3000 rpm?

[BudgetBoy]

Do these not screw in from the float bowl side (iirc) 8mm i think. I can get the kit to rebuild them but not "Just" the emulsion tubes.(Not cheap)

Honda VFR400RK/L/N NC30 '89-93 115 mains and 38 pilots.(Jap) uk is 120 main

Check you pilots as some have 35 pilot jets in and some have the 38's (FRONTS)

rears are 118 main & 40 pilots again some have a 35 pilot..(jap) uk is 122 main

And i would say its your pilot area where you are running rich at 3k. So check the pilots as well. Also your A/f mix screw might be set wrong or they could have a snapped tip.. (2.25 turns out btw)

The float needle might have wear on the tip allowing more fuel in the bowl, causing over fueling. So check those as well.

Im sure greybike will have data and stuff but hope that helps anyhow.

[thefatman]

They do suffer from carb icing a bit at this time of year, depending on what day of the week it is.

I think I may have a spare set of nc35 carbs you can borrow which helps with the power delivery i'll take a look at the weekend.

[marcaztls]

Here's the pic of the fiche I'm looking at. Hopefully you can see what I mean about the emulsion tubes not being touched by the needles. Numbers 15 and 16 are the emulsion tubes.

ZX9R's are similar and wear the needle guides out which can't be replaced.

[lorenzo]

And i would say its your pilot area where you are running rich at 3k. So check the pilots as well. Also your A/f mix screw might be set wrong or they could have a snapped tip.. (2.25 turns out btw)

The float needle might have wear on the tip allowing more fuel in the bowl, causing over fueling. So check those as well.

Float's are good, A/F screws & pilots are all good, correct sizes, as are the mains, but just to confirm, the issue isn't at 3k, it's 3k wide, starting at 6k and going up to 9k.

I can see your pic Mark, yes, but it's not clear what the needles sit in, to my eyes at least. If the guides can't be replaced and that's my issue then I'm fairly fucked, aren't I?

Tim, what's the deal with carbs off a 35? They're slightly smaller, aren't they? Not that it's an issue in terms of power etc, but do they fit the same rubbers as a 30? How easy is it to set them up? To be honest, I don't want to be faffing about doing tiny little carb tweaks all the time to my daily ride, I really can't be arsed, not with how much of a pain in the arse carbs are to get on and off especially.

[marcaztls]

You can't see what the needles sit in on the fiche pic because the parts aren't available seperately if the design of carb is the same as I'm thinking it is.

The guide is a brass piece pressed into the carb and only comes with the main body.

Again, this is all from my shockingly bad memory but I've replaced a few sets of carbs on these bikes to cure just that sort of problem so I'm pretty sure the needle guides aren't replaceable or I'd remember doing that.

VFR400's do seem very prone to just these sort of symptoms you're suffering in my experience and like I said, I've swapped carbs for second hand ones, sometimes made them worse, sometimes made them better which all points to wear related issues. Owners have sourced their own carbs and I've cleaned them prior to putting them on and balancing them.

I've got one customer who's NC30 behaves exactly like yours but doesn't want to/can't afford to do anything about it. It goes well above 9-10k as far as I remember, but really struggles to pull through the midrange. Ben Miller from Classic Bike.

[lorenzo]

I've a vague memory of reading somewhere that the problem is dynojet needles are too hard, harder than the brass (which I thought was emulsion tubes), and hence wears the carbs rather than themselves. Of course, it could be that my needles are worn which'd give similar results, I would have thought!

[marcaztls]

Nope, DJ needles do have that effect quite often, you're right Loz.

[thefatman]

NC35 are a straight swap, just needing a new throttle cable. Much more forgiving on the jetting as well because of the more modern design or some other unknown factor.

Rick Oliver does a set of replacement needles that sort the 6-9k flatspot on bikes fitted with a race can.

[lorenzo]

I might drop rick oliver a line, see what he's saying, but if stuff's worn in the carbs which isn't in the kit then I'll be looking for new carbs I suppose.

What's the difference between UK and import carbs, jetting aside?

[thefatman]

The numbers stamped on the side are different, the slides, needles and emulsion tubes. You can swap over all the bits though.

[lorenzo]

Do RVF carbs make a difference to economy either? I suspect that some of this is due to the megafuel middle in combination of having somebody that's much too big for the bike sat on the back, but I've never got 90 miles out of a tank, sometimes, if the commute has been dry all the time, it won't even be past 75 miles until I'm on reserve.

[CMSMJ1]

RVF carbs are nice - they work lovely. get them suckers fitted

[lorenzo]

Just to bring this thread back to life, a week or two back I finally managed to get a set of RVF carbs I bought working OK. I got my hands on them before christmas, swapped the jets for 110's, which is pretty common for an NC30 on these carbs (racier cans tend to want 112's), but cracking open the float bowls just meant that they leaked like a sieve due to rock hard gaskets. I then got a new set of gaskets, refitted them, then found that the floats weren't sealing, so bought a new pair of those (2 floats were cool and as they wear both the float and the seat simultaneously I didn't want to swap them just for the sake of it), which stopped them leaking and finally had me a running bike, of a fashion. The next problem was that on a neutral or slightly trailing throttle the bike'd almost drop onto 3, but would idle OK, which I thought odd. Another strip down this time revealed a couple of issues: Firstly a pilot jet was partially blocked, I could just about see a tiny pin-prick of light through it, but much less than the others, so that got cleaned out, and also I must've messed up the float height setting, with them all being at 12.5mm, apart from one at about 8mm. Sorted that out and it's great, feels much smoother, no hesitation in the pick up from way down low, and gives useful control from right down at 4000 revs, which on a 400 is about as low as it's ever going to go. It's not perfect, there's a tiny bit of a burble on a closed throttle, which I need to get it on the dyno for really, but I'm suspecting pilot screw settings or maybe float heights, but I'd like to know which way to go on them before taking them off again. The big news though is the economy: My previous best on a tank was 92 miles, averaging about 85 with the VFR carbs. I've just flicked it onto reserve on my way into work this morning at a heady 102, which by my quick mental maths probably works out as an improvement of about 5mpg, perhaps a bit more (somebody do the maths, if you're interested, £14.50 for a full tank on normal cooking petrol). At that rate it'll only take me, erm, 2 years to pay back the cost of the carbs...