NC23 Carb issue?

[DK-Tandy]

when you press the starter button should fuel go from the bottom of the carbs through my restricters and into the engine??

once i disconnected my carbs from the engine and pressed the starter button no fuel came out from the bottom?

i was manually pouring fuel into the fuel pipe which connects to the tank and fuel was also coming out the pipe which sites centre of the carbs, which is (i presume) how the fuel enters the carb?

so its like my fuel magically diappears once entering my carb?
so it must be leaving from an overflow pipe somewhere?

any idea's guys??

[CMSMJ1]

the engine sucks the fuel into itself. the carbs do not magically pour it in... The carbs have float bows that fill ith fuel adn have a float needle that seals them and should stop them overflowing.

Go and find out how a CV carb works - look at some pictures and it will all make sense.

*patronising alert*

Please go and find out about how these things work before you take them to bits. There is no point taking it all apart if you don't know what you are looking for.

*end patronising*

So, what is the actual problem anyways?

[Wozza]

when you press the starter button should fuel go from the bottom of the carbs through my restricters and into the engine??

Yes, in vapour form, mixed with the air.

once i disconnected my carbs from the engine and pressed the starter button no fuel came out from the bottom?

The fuel is 'sucked' through the main jet when air passes through the carb, so no, fuel will not move if the carbs are not attached to the engine. You are perhaps confusing with the fuel pump - this delivers fuel TO the carbs, but nothing further (provided the floats and float valves are working).

i was manually pouring fuel into the fuel pipe which connects to the tank and fuel was also coming out the pipe which sites centre of the carbs, which is (i presume) how the fuel enters the carb?

If you mean the main fuel feed pipe that goes from the pump to the carbs, yes.

so its like my fuel magically diappears once entering my carb?

Yes, it 'disappears' into the air.

so it must be leaving from an overflow pipe somewhere?

If it was overflowing you would notice as it would be pouring out in liquid form.


Have you still not got the bike running since fitting the restrictors?

[DK-Tandy]

No, I've still not got it running! While can't they be as simple as 2strokes LOL. When I get some time I will check the spark plugs to see if im getting any sparks. I know it's going to be something stupid. What would be the next step if I'm getting a spark or weak spark ?? Or what if I have no spark? Also does it matter how I start it, in gear with clutch in? In neutral clutch in? Or just by pressing button?

[DK-Tandy]

ive just found these from Fireblades forum (http://www.fireblades.org/forums/honda- ... 00-rr.html).

just so you can read them, there is some important info in there. which could be useful to me and others..

I have now gone to start it and, yes you've guessed, it wont start! Now bearing in mind it hasn't been rode since that time here is a check list of things i have done:

1. Charged battery.
2. Drained old fuel from tank and replaced with new fuel.
3. Drained old fuel out from carb float.
4. Checked that plugs are sparking on turn over.
5. Checked that fuel pump is working by disconnecting from fuel rail.

The bike was on paddock stands front and back for the duration so i have no reason to suspect anything major, however i have just run out of ideas as the bike turns over but does not catch at all! i tried with the choke out and in and also with the accelerotor fully open but to no joy. On a couple of occasions it has back fired when trying to turn over which lead me to believe that fuel was being burnt in the exhaust.

How are the plugs -wet? I assume they are gapped properly and sparking sufficiently. Intake/Compression/Power/Exhaust

Air supply stopped?
Jets clogged?
Valves OK?

What is the battery votage? Does the regulator work ok

You need to get the plugs out. Verify their wetness (health). Spray some ether... see if it will grab. If it does... then you know you have a/ lack of fuel/ lack of flow/ timing is off/ valve is bent.

A compression check woud also be a good check. I believe they made an extension for a 10mm wrench that dropped down into the cavern they put the plugs in.

you could try shooting the ether into the carb intakes...but the plugs would be alot better, and you could clean them first ......if the bikes was running fine before you stored it, it's not something mechanical

Biggest problem I ever get with starting is after washing, usually when lightly spraying water through the radiator to clean the crud out of it. Water gets back on to the top of the head and WILL find its way through the plug covers enough to make it nigh on impossible to start if I don't take it for a run straight after. It's a pain in the arse because, as you've already pointed out, there not a lot of room in there to get to the plugs.

After taking the tank off, you'll have to take off the coils. Just undo to the two mounting bolts and the whole unit will come away. Don't forget to mark which coil goes to which plug. Then pull back the rubber shield and this will give you access to the plugs. The best way to get the plugs out is by using a standard plug socket with a cut-down length of allen key to act as a drive (From memory a 10mm key drive does the trick here. Then just use a 10mm spanner to undo the plug via the allen key. This will give you the room you need to get the plug out.

Also, change the fuel filter (located just under the fuel tank on the bike's left side, under the fuel cut-off switch), it will only take about 1-2 minutes. They get clogged up after time standing around so it's good practice to replace it.

The 400's regulators love to sh*t themselves if left for a while. The only time in a year and a half that mine backfired was about 30 seconds before the regulator went bang and took out the wiring in my headlights and melting the high-beam fuse! If its died, for gods sake don't replace it with another honda unit. Get a after-market type with cooling fins!

To solve it easily, I remove the tank and then use a tube leading into a bottle with fresh fuel hanging above the bike to allow a gravity feed. It seems to solve the problem.

had the same problem.. turned out I had an intermittant fault on my fuel pump... so I took it out!!!! I've been running on a gravity fed system for the last 2 weeks.. the tank is connected straight to the carbs with just the inline fuel filter on..

have you checked the floats and the vacuum slides that hold the needles? Sometimes those rubbers can hide a tear in them really well!

another check to do is to try and bump start it, when i first brought mine it was a non runner, however first bump start and off it went, turns out that the clutch sensor switch was the problem on the starting circuit. I shorted the wires and have not had any problems with it since. good luck!

[The Novice]

First - Just check if yours is sparking..............

[DK-Tandy]

WOOT, she fooking starts :D

i found zee problem

i re-routed the fuel straight from tank to carb instead of through the fuel pump so it runs through gravity fed fuel..
i'll try linking back to fuel pump to check whether my pump is faulty or not or just the time of month for my bike.

its a bit rough on the idle so the carbs may need adjusting, but she definately starts