VFR400 NC24 runs for 3 minutes then .....

[Pirates Cove]

Hey all.

We took the carbs off because we could not lean then out at all. Turns out that they were all set to 10.8mm instead of 6.8 mm. One carb had some sediment and the pin the float was on was stuck.

Now set to 6.8mm is much better but still running rich (with 115 jets) I think the pilot is set to 1.5 turns so will try 2 turns then 2.5 to see what happens with the plugs.

At night it runs pretty good especially at small throttle openings. hot during the day it has a large flat spot between 3000-6000 and the more throttle the worse it is.

Thanks for all your help

Mark

[Neosophist]

Hey all.

We took the carbs off because we could not lean then out at all. Turns out that they were all set to 10.8mm instead of 6.8 mm. One carb had some sediment and the pin the float was on was stuck.

Now set to 6.8mm is much better but still running rich (with 115 jets) I think the pilot is set to 1.5 turns so will try 2 turns then 2.5 to see what happens with the plugs.

At night it runs pretty good especially at small throttle openings. hot during the day it has a large flat spot between 3000-6000 and the more throttle the worse it is.

Thanks for all your help

Mark

115 jets all round are correct. Do you have the emulsion tubes in the right carbs? The rear cylinders have an extra hole in the emulsion tubes.

Have you done anything to the airbox / is your airfilter clean and standard. (and are your plugs good)

That 3000 / 6000 flat spot is likely to be fixed by adjusting the needle height to increase mid-range mixture.

I can't remember off the top of my head the floatheight for the 24 carbs.. istr that the nc30 is 6.8mm, i'll check if it's different.

[wullvfr]

the float height is 6.8mm but the standard jet size is 112/110...........

this is maybe why it is still running rich..



william

[Pirates Cove]

Hi all.

The airbox has a custom low restriction foam filter the sparks are new u25 (I think) Nippon denso as spec.

The only other weird thing is that the idle changes between 1500 aprox and 2500 aprox. The carbs have no air leaks.

Thanks Mark

Happy new year from Thailand

[Pirates Cove]

Carburation:-
Carburettor Type: CV
Carburettor Model: VDE2
Pilot Jet Size: 35
Main Jet Size: 115
Float Height: 6.8mm
Pilot Screw (turns out): 2.5
Idle Speed: 1300rpm +/-100rpm
Spark Plugs:-
Cold Climate: NGK C7EH9 or ND U22FE9
Standard: NGK C8EH9 or ND U24FE9
Hot Climate / High Speed Riding: NGK C9EH9 or ND U27FE9

specs from http://72.14.235.132/search?q=cache:sH6 ... =clnk&cd=3" onclick="window.open(this.href);return false;

Mark

[Cammo]

The airbox has a custom low restriction foam filter the sparks are new u25 (I think) Nippon denso as spec.

The only other weird thing is that the idle changes between 1500 aprox and 2500 aprox. The carbs have no air leaks.

I would put a standard air filter in and see how it runs, the foam probably makes it run very lean (usually lean when you open the throttle and it performs worse like yours = foam air filter).

The idle fluctuation sounds like the carbs need balancing.

[Neosophist]

the float height is 6.8mm but the standard jet size is 112/110...........

this is maybe why it is still running rich..



william

The standard JET size is 115.

112/110 is INCORRECT for the NC24 and is only applicable to the NC21.

[Neosophist]

Carburation:-
Carburettor Type: CV
Carburettor Model: VDE2
Pilot Jet Size: 35
Main Jet Size: 115
Float Height: 6.8mm
Pilot Screw (turns out): 2.5
Idle Speed: 1300rpm +/-100rpm
Spark Plugs:-
Cold Climate: NGK C7EH9 or ND U22FE9
Standard: NGK C8EH9 or ND U24FE9
Hot Climate / High Speed Riding: NGK C9EH9 or ND U27FE9

specs from http://72.14.235.132/search?q=cache:sH6 ... =clnk&cd=3" onclick="window.open(this.href);return false;

Mark

Thats my website :)

[Neosophist]

Hi all.

The airbox has a custom low restriction foam filter the sparks are new u25 (I think) Nippon denso as spec.

The only other weird thing is that the idle changes between 1500 aprox and 2500 aprox. The carbs have no air leaks.

Thanks Mark


Happy new year from Thailand

The floating idle is usually air leaks. If you have some WD40 or similar maintainance spray, spray it over the carb rubbers while the engine is running, if it changes the idle speed there is air getting past the rubber seals.

have you balanced the carbs? that might affect it too..

it could be a blocked idle jet? have you sprayed the carbs out with compressed air?

[Pirates Cove]

Ok we have got it setup 95% now.

I suspect that everything was well carboned up and now it is running right its cleaning it out.
Idle is stable and apart from a slight flat area 4000-6000 if you roll the throttle on too quick.

Its awesome fun riding around Chiang Mai with it now.

Thanks for all your help

Mark