Carbs

[Barry20383]

Still having problems setting up the engine
The plugs are getting fouled and black.
Don't know weather to reduce the float level as i have 1.5 spacers under the needle valves could
go for 2mm.
I have found if the choke is pushed in the engine races this is the problem i had before changing the carbs.
I have noticed that the air regulating screws are different one has a sharp point the other has a flat front no point is this correct if so which carb is fitted with each one.
Thanks Barry.

[Keith Clements]

Barry.
Look at the idle jet needles on your spare carbs. I think they should be pointed.
Personally I would not use the carb with the wrong jet as the seat may be damaged.
As we have said before in this thread set up the throttle screws with the linkage disconnected. If it will not idle slowly then the recon butterflies are not shutting.
You could try resetting butterfly but I would replace that carb and see if the problem is fixed.
The plugs are black probably because you are running on choke.
Does it start without choke when cold?

[Barry20383]

Have not tried to start without choke will try that.
The spare carbs have pointed air jets will change one over. The car idols ok but shoving in the choke makes the engine race. This was the same with the old carbs that's why i changed them. At least the engine is now running that's a big step forward
I am using NGK B6HS i bought these as these were already fitted is there a better plug to fit.
Thanks Barry .

[nigel jarrett]

I have never come across a flat ended mixture screw ,as keith says be careful that the seat is not damaged,have you checked the jet sizes against those listed for the Javelin,there is also a jet in the body near the butterfly,these quite often have been damaged trying to get out.

[Keith Clements]

Barry,
Please do not start changing things but fix what is wrong.
As I said fitting the other idle jet may well screw it up.
It is racing because the throttle is open .
Fix that first.
If you screw the throttle stops back so there is a gap and it is still racing, I have told you what is wrong.
The engine should stall with the stops fully back.
This is a common problem with poor reconditioning.

[Barry20383]

I am surprised the Jowett spares dept have supplied such poor re con carbs. I did intend sending them elsewhere but no work is being done due to Covid.
Looks like i am stuck with them as the club wants the old ones back soon. I did check the butterflies when closed before fitting them i could only see a very small amount of light through them almost nil.

[Keith Clements]

It may not be the fault of the reconditioner but the supplier of the new butterfly valves.
It is not possible to recondition the throats, so if they were not good to start with then you will not improve them by fitting new butterflies.
In my experience the old butterflies are often better than new ones as they have bedded in, but if the spindles were worn for a long time even then the butterflies will not fit with new spindles.
Please read the topic on reconditioning carbs and you will see what is involved.
It looks like you may have at least one carb which is bad.
Of course, the symptom may not be caused by what I suggested, but is my best guess.
Try loosening the two butterfly screws and closing throttle hard. then carefully tighten the two screws. This might close up any gap.
If you run your finger down the throat you will feel how worn it is where the butterfly contacts it.
Why not speak with JCS again?

[Keith Clements]

https://www.ebay.co.uk/itm/Zenith-30-VM ... 3756057416
https://www.ebay.co.uk/itm/Zenith-30VM- ... 4561081066

Should be possible to transfer some components to make this work in a Javelin.
But buyer beware there may be a reason it has survived this long without being used.

The 'club spares service' is staffed by members like you who volunteer their time and expertise unpaid and do their best to support other members. You are lucky they have provided a service, unlike the other supplier you were looking at.

[Nick Webster]

Keith, I think looking at the back story here, with various things like leaks and the emulsion block gasket upside down, my question would be whether the actual reconditioning is done by an expert, unpaid volunteer or not. You have previously suggested checking the carb body for wear in the area of the throttle disc. If this was the case then it it should have been rejected for reconditioning. I have only admiration for the the effort volunteers are putting into providing the sales service but I am wondering if perhaps an effort to keep affordable prices is compromising the quality of spares. Confusing and frustrating this story may have been, but certainly we should not be settling for "you are lucky to have it".

Nick

[Keith Clements]

Nick, I have been in touch with JCS and hope Barry contacts them again. Having rebuilt many Zeniths I know many of the issues, only some of which have been discussed in this topic. I learnt from https://www.carburetterexchange.co.uk/ when I visited them back in the 90s that bench testing the carbs after refurbishment was necessary. No doubt their prices are higher than JCS and their lead times are very long and maybe they are even longer now.

I am sure JCS do try to keep prices as low as possible, and sometimes that may increase the risk of a problem. Presented with a carb that came from a running engine with obvious worn spindles you could just ream and rebush. Of course that would not produce a brand new carb. but would still cost perhaps £80 to do.

If the carbs are supplied by the member with some knowledge of their existing condition and problems then that helps. If you get them from a scrap heap then you are starting with a completely unknown situation. Once I rebuilt a carb taking tens of hours only to discover the thread in the input had stripped beyond repair. On another the float chamber body was distorted. A damaged idle jet seating would be very difficult to see. And would you be fooled by replacing a gasket the same way as it came out?

The cost of refurbishment in time and expertise is extremely difficult to assess as many issues may require skills and tooling that would not normally be required. Would you pay £200 for a refurbishment that failed because of an inherent fault in the donor unit?

All Zeniths I have seen do have wear at the butterfly but assessing whether that will cause a closing issue is not easy. Replacement butterflies are not shaped to fit as original . I have not shaped or lapped them in which may be an answer to the closing problem. But this would be labour intensive.

Barry's problems may well not be carb related which is why I keep asking him to replace back to the original, either in whole or in part, to see if symptoms change.

[Nick Webster]

Keith, thanks for your comments. I think possibly some things are perhaps best not sorted out on a public forum. You will be aware though that reproduction spare part quality is something that blights the entire classic car movement and it benefits us all when issues can be fed back to the source.

I will however respond to your comment about replacing a gasket incorrectly because that is the way it came out. No, never. In fact having nipped out to the garage and tried again with a dismantled emulsion block I might say that in that case it defys credulity.

To the matter in hand. We have had some discussion about idle needle shape. There is indeed more than one profile, which I have endeavoured to photograph. The one with the sharpest point comes from a C1161 and the other, a C1334. In the past, tempted by the nice grippy bit that characterises the blunt needle I had attempted to insert these in the "wrong" carb but because they did not quite feel right when screwing in (I think because of the shoulder just visible in the picture) I abandoned that plan and then realised the difference. I would imagine if you had a pile of needles on the bench to use the very subtle difference might go un-noticed. It does make a difference and the correct needle should be in the correct C number carb.

Nick

Needle.jpg

[Barry20383]

Will check the carb numbers and fit the correct needles.
The problem is the two carbs had one of each needles.
Could it be that one carb has the wrong needle or the carbs have different numbers an odd pair.
I could not send my carbs for recon as Carbs exchange and other companies not taking on work due to covid or have very long delivery dates. I would have rather paid a lot more money and had a lot less problems.
I didn't have to contact Jowett spares as they have contacted me twice about returning my old carbs i have explained that i have not got the car to run properly yet.
Thanks for the advice about the needles and carb numbers will check this.
Barry.

[Keith Clements]

I agree with Nick that fitting the emulsion gasket the wrong way around is difficult to believe. I usually leave that gasket alone. Note there are different shapes as well on the 30VM noted somewhere on JT by Scott Renner.
The C number is stamped on the body , but at some stage the bowls may well have been swapped and thus not match that C number. The jets in the bowl can be checked but note I have found that the the jets do wear and I check with a set of drills very carefully. Once again see my carb rebuild thread.
After 60 years of abuse many carbs have faults. Jowetts were cars that on the whole were never well maintained until recent times and so carburettors may well have suffered at the hands of amateurs.
I have about 60 30VMs where all manner of issues manifest themselves.

[Barry20383]

Have checked the carb numbers they are C1161M which as you mentioned should have sharp pointed air jets.
Have taken a jet out of the old carbs as they have the same number and fitted it both now pointed jets.
Started the engine and with both jets at 2 turns out seems a lot smoother.
I started the engine on choke with both stop screws fully out and pushed the choke in and the engine stalled as you suggested .

[nigel jarrett]

Due to the weather I had a spare hour this afternoon so I dug out my selection of carbs ,on deep inspection they were C1334 ,C1161, C1171 all marked supposedly for a Javelin ,all had a selection of different jets with the C1171 being quite a bit different in design This just goes to show you have to be careful not think that everything is as it was when it left the factory