RB30 Nikki carby auto choke issue

[dom14]

Hi guys,
Please have a look at the photos attached.

Carby has been rebuilt withe a kit, but it still doesn't idle on petrol on correct choke setting.

I've aligned the index marks on the choke body with carby body.(see picture)

But it's no good.

Only way to start the car on petrol and have the idling going is to turn the choke towards 'rich' setting(anti clockwise).
Then again, even after the engine is warmed up, the choke butterfly won't fully open. It only opens slightly even after fully warmed up(See picture)

Am I right to think that this causes performance and fuel economy issues(running too rich all the time)??!!

I've adjusted the 'idle speed screw' and the 'idle mixture screw' to RPM 850 ish, which I think is fine.(see picture)

Is this a problem with a faulty choke thermostat?! Do I need to replace this unit?!

Is there a way around this without renewing the choke thermostat?!!

Thanks for any help.

[Alitis007]

Yes that will cause poor economy but are the springs that work the mechanical side of the choke cam on correctly?? Under that thermostat spring, are both the stoppers in place?? Can you open the choke flap fully by hand??

[dom14]

Hi mate,
Yes, I put it back the way it was, after I rebuilt the carby. I do not fully understand your questions mate. So, I added a photo, so hopefully you can guide me. I marked the thing which I think are the stoppers. Please let me know if I'm wrong. I think I was able to open the choke flap fully by hand. I will double check it again. I was able to open it by turning the thermostat towards 'lean' setting(clockwise), but of course that wouldn't help with starting the car since the choke flaps stays open and wouldn't close when I start the car.

By the springs, did you mean the springs, did you mean the outside spring that's holding the the choke shaft to the bottom side(i think it's fast idle cam)?! That spring appear to be fine. I couldn't see any tension loss either. I added a picture to make sure I understand what you meant.

BTW, Haynes manual says, if the choke flaps doesn't fully open by the time the car if fully warmed up, then the choke thermostat is defective. I'm not sure that's all true. In my case, choke doesn't fully open, but it doesn't fully close either(unless I turned the thermostat towards 'rich' setting. So, this is why it confuses me, whether the choke thermostat is the defective one, or whether there's another defective mechanism connected to the choke causing this issue!.

Thanks mate

[Alitis007]

You didn't fit it correctly I THINK,

You see the C shaped bit on this ( i took a screen shot of your pics)

26888

Should fit onto the lug for the choke flap here

26889

So start wit the C part at 3 O clock then turn it anti clockwise and you should start to feel tension when the mark on the black cap gets close to the carby marks. The more your turn the black cap clockwise past the marks you should feel more resistance being applied to the choke flap. Do you get what i'm saying ??

The spring looks correct, it was opening when you turned it clockwise because the C part of the thermo coil was pushing it open IMO.

[dom14]

Hi mate,
Thanks for the quick reply. I couldn't view both attachments. When I click them, message comes up, "nvalid Attachment specified. If you followed a valid link, please notify the administrator".
I thought I did it the way you described here. I did feel a tension when I turned it, let me make sure whether it was clockwise or anti clockwise. I will open it up and do it again, and see if I can get it right this time.

BTW, if the choke flaps open when I turn the thermostat clockwise, doesn't that mean I fitted it correctly?!

Thanks mate

[Alitis007]

No worries i'm trying to help you and work on other people's cars at the same time without being seen by the boss lol.


Now if you turned it clockwise and the flap opened on its own and could be closed by your fingers easily CORRECT, if you turned it clockwise and could not close the choke flap or was very hard to close the choke flap INCORRECT.

[dom14]

Hi mate,
Thanks for the help. BTW, do not get caught by the boss, if you lose the job, you won't be able to help me and besides you might have to start charging me for this information. :))

Yes, it responds to that test good. So, I reckon I fitted it correct. I am adding more photos to get some idea of what may be causing this issue, and hopefully with your help I can find it.

The choke flaps are slightly opened when it's cold and idling, but never fully closed and doesn't fully open as the engine warms up.

I discovered that the reason it stays in that position(choke flaps) are that 'fast idle cams'(i hope I got that right) stays in one position stuck and won't move. See the picture. It's the plastic bit with three positions to rest the idling setting, I think. I can get the choke flaps to move and close by moving the throttle. Moving the throttle causes the plastic 'fast idle cam' bit to release, which in turn frees the choke flaps and I can close it by turning it.

Is this thing the real culprit?!!

[Alitis007]

Its all good mate you could say i have a form of job security lol

As far as i know when the motor is cold before the first start, when you kick the throttle the cam that your calling fast idle should flick closed the choke flap. When the motor warms when you kick the throttle again, the tension on the thermo coil is lost from it heating up and the choke flap opens.

I'll see if i can find a carby thats similar to yours and try to work it out, but where are you located??

[dom14]

Hi mate,
I'm in Melbourne.
It would be great if I get hold of a carby repair manual for this Nikki carby.
Do you know where I can find a one?

I don't think the carby's choke and 'fast idle thing' is doing what exactly it suppose to do.
It's bit sluggish on petrol(no power, and hesitates a lot)
I think the reason is it's not getting enough air 'cos of the flaps not fully openning?!

[dom14]

Its all good mate you could say i have a form of job security lol

As far as i know when the motor is cold before the first start, when you kick the throttle the cam that your calling fast idle should flick closed the choke flap. When the motor warms when you kick the throttle again, the tension on the thermo coil is lost from it heating up and the choke flap opens.

I'll see if i can find a carby thats similar to yours and try to work it out, but where are you located??

Please have a look at the photos mate. I was told by the RACV mechanic(an older fellow), that this vent suppose to be opened when I start on petrol or run on petrol. Though I found, it doesn't make much of a difference when do that. If the choke thermostat index marks are aligned the way it suppose to be, car never starts on petrol(obviously because choke flaps stays open).

I'm not sure what exactly this cable vent thing is for. I hope you can help me out here.

Cheers

BTW, it's great you have job security. :beer:

[Robo]

I did some research a while back and believe that particular mixer (A200 or something) is a bit to restrictive for petrol.
so you pull the cable to open up the mixers throat somewhat to allow better air flow when running on petrol

[dom14]

I did some research a while back and believe that particular mixer (A200 or something) is a bit to restrictive for petrol.
so you pull the cable to open up the mixers throat somewhat to allow better air flow when running on petrol

Thanks mate. I will test drive it again to see pulling on the cable to open the mixer vent makes any difference to the starting and performance on pertol. I managed to start single crank Friday morning without having to pull the cable. So, it's confusing the living something out of me at the moment. :))

I did manage to find a problem though. The cable that moves the mixer vent has come loose, the outer was sliding along the holder bracket, rather than inner moving and properly opening/closing the vent.
That may have caused some drama as well.
I will get back with the test drive outcome.
Cheers.

[Robo]

A thought,
may not make a whole lot of difference, mixer is good for much larger capacity engines.

note- Australia ebay A200 mixer inc cable new around $250.

[dom14]

Yeah, I did couple of test drives. It wasn't making much of a difference. I think, when on LPG, the engine doesn't like when I pull the cable to open the vent. I guess that's for obvious reasons. For petrol, not much of a change.

[JC Black betty]

hey mate just wondering could u send me some pic of all ur vaccum lines i think i have few around wrong way. Cant find a diagramme anywhere online if ya could help me with this i would be stoke as i have been stuck on it for 2 days :S cheers buddy

[JC Black betty]

i had this same problem pulled carby off and on the bottom is veiwing screw for jet i think if u pull that out u will find that it is covered in an lpg by product red sticky shit. Wat i did was pull carb off cleaned the crap out of it with carb cleaner took the jet screw out and clean all in their put it bak on than bam ran fine started fine etc an idea anyway mate

[GQ TANK]

I had a problem where they truck was ideling very high - around 1400, it was due to the fast idle cam being in the wrong position when I rebuilt the carby
The bit im interested is the whiteplastic thing that sits below the idle pot.

I cannot ell if yours is in the correct positionvia the photo.

Also the TB42s carbys are very similar - ( I used a rb30 carby as a sample when I rebuilt my tb42 carby)