VFR NC30 idling/ revving issues

[VFR-Element]

Hi,

I have a NC30 that has been standing for about a year, the only reason for that is CDI issues. I bought a De-restricted CDI from Japan, replaced the Spark plugs and checked all fuses and connections. I laso gave the carbs a once over (cleaned jets, pilot jets, emulsion tubes, floats and the the fuel inlet ). the bike was running perfect before the CDI crapped out. Now the bike idols @ between 4000RPM and 6000RPM and does not rev past 8000RPM when cold and 9000RPM after optimal temp reached. I've also balanced the carbs and checked all the air screw settings and the bike is still the same. I've checked the carb connector boots and they seem worn but not badly enough too leak. Running out of ideas. Going to test the CDI today with a VFR thats currently running eliminating that option. Please help...

[CMSMJ1]

Welcome to the site

SO..what is the history of the bike Has it been changed in any way from standard jetting etc?

Which CDI did you get? There are many reports of these derestrcited CDIs being shite

rf the high idle - is the choke not stuck? Are the throttle cables set right? Is the idle adjuster screwed out to stopit revving it's arse off?

[VFR-Element]

HI,

Bike was running perfectly but the regulator decided to stop regulating and blew everything. I re-coiled the stater and replaced the regulator. I also replaced the battery, spark plugs and spark coils. the carbs were standing with old fuel cause i didnt think it would take so long to fix... i've done everything i could think of on the carbs. the cabling are all perfect and the carbs have been balanced. I even tested the levels The only thing i can think of at this stage is either carb connector boots or CDI. It is a replecement CDI Unit (New from Japan, just in time) and is not a HRC module. any ideas?

Thanx

[Drunkn Munky]

and does not rev past 8000RPM when cold

easy now fella, she wont be going anywhere if you keep treating her like that

You havent brought one of those dodgy chinese derestricted CDI's have you?

[Neosophist]

So many things been altered so you need to do some logical investiagtion.

Firstly check the electrical system out. Battery voltage at 5000rpm, altenator output at 5000rpm.

The RPM being really high doesn't tally with the Ignition box though, the bikes throttle control is manual and not controlled by the ignition box. Since it is running i'd leave the ignition box alone until you get the idle sorted out.

Im going to assume that the carbs are clean, all jets and air-screws are set to stock factory settings. Make sure this is right first.

0. Remove the airbox lid and filter so you can see the carb velocity stacks (trumpets) and butterflies. check they are all shut with the throttle off. If not look at idle screw (point 1, and throttle cables point 2)

1. Check the idle adjuster screw, this manually opens the butterflies on the carbs more or less depending on how far it is screwed in. Try screwing it almost all the way out to isolate this.

2. The throttle cables will also open the butterflies if incorrectly adjusted. Try operating the throttle with the engine off and observe the butterflies from the velocity stacks, they should open and close smoothly.

3. Providing you have butterflies that are opening and closing ok, check that the choke levers engage and disengage properly, if you operate the chocke you will see how it work, it pulls a series of connected levers out of the carbs, these should retract almost fully when the choke is switched off.

4. The only other cause i can think of at the moment of the high idle is an airleak on the carbs, the engine will suck in extra air which gives the high idle, this can be due to badly fitting carbs, split carb rubbers etc. You can check for this by spraying somethign flammable (brake cleaner, easy start) aroud the carb rubbers while the engine is running, if you notice a change in rpm then you have an air-leak on the rubbers.

Once you get the bike ticking over at idle properly, have a ride of the bike and try another ignition box, the chinese ones are known for being crappy but usually the bike doesnt run at all or missfires a lot, they sholdnt affect the idle speed.

[Cammo]

So many things been altered so you need to do some logical investiagtion.

+1. Difficult to diagnose since so much has been changed.

How did you balance the carbs? Do you mean you synched the throttle butterflys with the carbs off the bike? be careful doing this, you can adjust them all to be open so much that the bike will rev high, no matter how much you wind down the idle adjustor. Have seen this before!

You can check if this is the case by taking off the carbs and seeing if all butterflys are closed and sitting flush when the idle adjustor is removed. Look carefully, not much air will need to get passed to raise the idle.

[VFR-Element]

So many things been altered so you need to do some logical investiagtion.

0.

1.

2.

3.

4. .

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I have done all these steps already, All cables are checked i even tested without throttle cable and idle screw not connected so throttle is as closed as it can be. The choke is disengaging, it was also one of the first things Ive checked as the bike rides as if it is already @ op temp but with choke not disengaged. the butterflies are flush when cables disconnected. The CDI is one of those damn Chinese things but the person who supplied it advised that it would either work or not, no in between. the only other thing i still have to do is check the carb boot rubbers properly. Also know that the bike was running with all these new changes with a second CDI from someone else's bike so none of the new parts is causing this, but that was a year ago when the bike 's original CDI broke. the only thing that changed is that i haven't touched the bike in a year so anything could of happened. I left fuel in the bike (I know not the best idea to leave the carbs like that) thinking that it would only be out of action for a couple of weeks at most.

I decided to take the bike for another test run and found that @ about 100m/h and @ about 9000RPM the bike sometimes feels like it wants to go but its being restricted. It's got the flat spot and every now and then it has this split second burst that feels like it wants to go but shortly after taps out again this happens constantly every other second or so. Any ideas, could my ignition coils be part of the limiting problem?

[VFR-Element]

So many things been altered so you need to do some logical investiagtion.

+1. Difficult to diagnose since so much has been changed.

How did you balance the carbs? Do you mean you synched the throttle butterflys with the carbs off the bike? be careful doing this, you can adjust them all to be open so much that the bike will rev high, no matter how much you wind down the idle adjustor. Have seen this before!

You can check if this is the case by taking off the carbs and seeing if all butterflys are closed and sitting flush when the idle adjustor is removed. Look carefully, not much air will need to get passed to raise the idle.

Carbs butterflies was balanced throats cleaned air screws set to factory standards. I have to mention that after the carbs were balanced it was idling less erratic and it revs cleaner between the revs currently available .
but the idling still very high.

I decided to take the bike for another test run and found that @ about 100m/h and @ about 9000RPM the bike sometimes feels like it wants to go but its being restricted. It's got the flat spot and every now and then it has this split second burst that feels like it wants to go but shortly after taps out again this happens constantly every other second or so. Any ideas, could my ignition coils be part of the limiting problem?

[CMSMJ1]

So, does it have bog standard jetting? Has the airbox been molested at all?

NOt convinced about the CDI to be fair - electrical stuff either works or it doesn't IMO.

Have you got another CDI to test?

[VFR-Element]

Yes, jetting standard as i bought it 15 in front and 18 rear. Air box in perfect nic and factory standard. Nothing funny have been done on the bike and thats why i dont understand. after i replaced all the broken parts (regulator, battery etc) i tested it with a CDI that i know works and the bike was running perfect. I sent my CDI in to see if it could be fixed but that took too long and i finally decided to by a new one after a year. I will be testing a different CDI on the bike today or tomorrow and will let you know if anything changes. If the coils earth is not connecting properly, could that cause it, or maybe loosing spark on the outside of the motor (Broken sparkplug cap)?