hey, i've done a good search of the forums but I'm coming up empty.

My NC24 is fuelling really badly. I've cleaned out the carbs and checked the sliders and jets and sync'd the carbs but the fuelling is running far too rich right through the revs.

Low end = ok
Mid = flat spot, no power at all.
Top = Revs fine

bike accelerates okay on WOT up to about 80-90mph (100 or so max) at the moment and at that point it just seems to loose all power, sometimes backfires on rolloff, and just dies, to get it going again I have to stop, put the choke on full, fire her back up and wait for the bike to stop spluttering and rev free before I take the choke off and ride away. Very annoying.

I have standard 115 main jets at the moment, a Viper can and the guy before me has put a pair of tights as the air filter to try rectify it running as rich (didn't seem to work). You can actually smell petrol on idle from the can, and fuel economy is none-existent. roughly 25mpg if i'm lucky.

What should I be looking at changing? I was thinking maybe a smaller (110) jet? the pilot screws at 2.5 turns out and as mentioned the carbs are balanced fine. The bike is going on a dyno soon, but I would like to get it running better before I hit the dyno later this month

quick update, as recommended by a friend I've changed the mixture/pilot screws. they were at 2.5 turns out, I've turned them in 1/4, then 1/8, both times improving the fuelling. Noticeable improvement in fuelling on acceleration. Still running too rich on full throttle and bike still floods 100mph+

l00k3y wrote:quick update, as recommended by a friend I've changed the mixture/pilot screws. they were at 2.5 turns out, I've turned them in 1/4, then 1/8, both times improving the fuelling. Noticeable improvement in fuelling on acceleration. Still running too rich on full throttle and bike still floods 100mph+

Sounds like it's running out of fuel at full RPM...

I had this when I had a dodgy vaccumn hose.. it was leaking and collapsing in under-itself at WOT.

This shut off the fuel and the bike stutter and die.

Had to choke it to get it running again.

I'd check the vaccumn hose (best to replace it) first :-)

Then i'd reccomend a Dyno to get a good fuel air graph so you can see exactly what the bike is doing, otherwise your stabbing in the dark.

Get a standard air-filter on it too, you cannot do anything before this... messing with the air-filter really really really affects these bikes.

115 jets are fine (standard)

Start with 6.8mm float heights, 2 turns out.

It's worth-while to check electrical charge and for leaks in the exhaust... rear-downpipes and collectors as both of these can cause backfiring.

You'll need air in the exhaust to cause a good backfire rather than just a pop. :)

I'll change the vacuum hose and get an air filter, thanks for your reply :) just a quick Q because I wasn't so sure when I took my tank up, I think the vacuum pipe fell off and I didn't see where it came from. I tried to work it out from what was mentioned in another thread, but does the vacuum pipe go back onto the smaller nipple by the tap? almost as if it doesn't fit on? I first tried putting it back on the bigger one but petrol came out of the smaller nipple when I turned the bike over so I guessed that was the vacuum one... jw because the pipe doesn't fit on that nipple very well.

Fuel shouldn't be coming out of the small nipples on the fuel tap, you must have a cracked diaphragm in the tap.

ozracer wrote:Fuel shouldn't be coming out of the small nipples on the fuel tap, you must have a cracked diaphragm in the tap.

thanks, I'll see about getting a fuel tap repair kit and sorting it

http://www.nrp-carbs.co.uk/honda_fuel_t ... ir_kit.htm

sound about right?

l00k3y wrote:

ozracer wrote:Fuel shouldn't be coming out of the small nipples on the fuel tap, you must have a cracked diaphragm in the tap.

thanks, I'll see about getting a fuel tap repair kit and sorting it

http://www.nrp-carbs.co.uk/honda_fuel_t ... ir_kit.htm

sound about right?

It does.. phone them up and see whats in the kit.

Sounds like were getting to the root of your WOT fuelling issues already :D

The tap unscrews apart, if you take it apart (drain the tank as best as possible / turn it on its side first)

You can see the internals of the tap.

Hold the diaphragm upto the light and see if you can see any holes for it.

Sounds like you have.

1. Leaking fuel diagrphram

2. Worn out Vaccumn hose