Quote from: Graeme on Sep 17, 2023, 10:44 AMLarry

I've just been through the same process with my Zenith.  After several attempts at putting a 'service kit' in it I went through the same cycle of having it run perfectly for a couple of days then going rich again with the bleed screw ineffectual.

Problem turned out to be a warped case and top, ended up spending best part of a day lapping them with wet&dry on a piece of glass, along with the wrong spec o ring in the aftermarket 'service kit'.  Got onto a local seal supplier who supplied some viton o rings and it's been a sweet runner ever since.  The kit o rings were the wrong compound and were going rock hard after a couple of days leading to leaks even after the case and top had been lapped flat.  this may be the issue with the reproduction Zeniths as well.

With the o ring size I was kind of flying a bit blind, and assuming the size in the aftermarket kit was correct.  They were 1 3/16 x 3/32, which was a standard size.  Does anyone know if this is correct?  I suspect that while this size seems to work, it may be a little small, although the next biggest imperial o ring would be too big.

Very interesting, I am wondering why a warped carb body would cause it to be too rich and the idle mixture ineffectual
I would have though any air leak would make it too lean
If I could fix my chinese Zenith then I would be happy to have a go

I did read why a warped casting causes a rich mixture. I believe it's something to do with fuel overflowing the float chamber into the inlet but not 100% sure. Admittedly it sounds odd.

I know we are all knocking the Chinese made Zenith, but there must be a fix. Mine is clearly flooding with fuel and bypassing any effect from the idle mixture screw. Most likely cause would be the float/float needle not cutting off the fuel supply.
I am tempted to start looking closer - might be quite simple as it has run perfectly. For example, if float has sunk it would always flood
Any other expert ideas or thoughts?
Steve

As it's new don't mess about with it. Contact the supplier. If you dismantle it the guarantee is void. Look for a genuine Zenith to refurbish.

With the reproduction Zeniths, I'd try a better o ring in one and see what happens. 

The rebuild kits and repro carbs seem to come from the same source, and after my experiences I'd be looking at the o ring in the repro carb, after checking the casting faces are flat.

Heya everyone...

In re the Zenith currently on Grover, before rebuilding it I did cook it and, very gently wet sanded it on a pane of glass.  See the pieces bellow.

The father-in-law helped with the timing a few weeks ago and the whole thing got worse - sputtering, not wanting to fire, and some light backfiring.  Last Tuesday we tackled it again and what figured out what was causing all of that - he didn't get the bolt that clamps the dizzy tightened enough.

Once that was dealt with I fired up Grover - started up on the first attempt and was idling well at 500rpms. We let it idle for about 20 minutes, no problems. Once it was warm it was idling at 550rpms. 

Took Grover for a spin and he handled really well.  Took him for another spin Saturday and all went well.

So... I'm going to wait and see how long it takes for the carb to start running rich again.

Now... if it does start running rich again we will try one of the new screws. This leads to another question - how can you tell if the adjustment screw spring is worn out?  I have several version of the spring, some have 5 coils and some 6 or 7.  Pic attached below as well.

Quote from: Alan Drover on Sep 17, 2023, 08:24 AMThe only place I know is BFS in the UK but I suspect carriage will be horrendous. I've found it in the spares catalogue but it doesn't have a part number and is not included in the rebuild kit. Is there a spring supplier in the States that could help?

Not sure if I know of a spring supplier here that could help. Diffwhine has given me an idea though... perhaps the chap that sent me the pic of the Chinese clones could tell me if they have those springs.

I see the spring listed in the exploded view within the following, but no part number.  Is there a link, or pic,to the parts list you have?

https://zenithcarb.co.uk/zenseriesiv#:

Quote from: Graeme on Sep 17, 2023, 10:44 AMLarry

I've just been through the same process with my Zenith.  After several attempts at putting a 'service kit' in it I went through the same cycle of having it run perfectly for a couple of days then going rich again with the bleed screw ineffectual.

Problem turned out to be a warped case and top, ended up spending best part of a day lapping them with wet&dry on a piece of glass, along with the wrong spec o ring in the aftermarket 'service kit'.  Got onto a local seal supplier who supplied some viton o rings and it's been a sweet runner ever since.  The kit o rings were the wrong compound and were going rock hard after a couple of days leading to leaks even after the case and top had been lapped flat.  this may be the issue with the reproduction Zeniths as well.

With the o ring size I was kind of flying a bit blind, and assuming the size in the aftermarket kit was correct.  They were 1 3/16 x 3/32, which was a standard size.  Does anyone know if this is correct?  I suspect that while this size seems to work, it may be a little small, although the next biggest imperial o ring would be too big.

I just posted a reply showing the parts I heated and sanded.

As to the O-ring - the one that came with my rebuild kit seemed to fit perfectly, but having never rebuilt a carb I'm clueless as to how it should fit. No clue what it is made of though.

In addition to all the above information in re the Zenith on Grover...

I had never rebuilt a carb before in my life, I always went through someone else.  I decided to do this one myself, figured if I could rebuild all the other stuff I rebuilt, why not the carb.

So, I got all the info I could, talked to several Rover owners, watched videos and took my time.

Once it was completed I reinstalled it and tested it out - fired right up.  But, something did happen that I wasn't expecting. The bottom part of the carb got icy cold and I noticed a small puddle of moisture at the base, the red arrow in the pic is pointing to it. This kind of freaked me out and the first thing that came to mind was leaking gas. 

I shut the engine down and started contacting a couple mechanics who I had spoken to about it beforehand. They told me that all was good and the cold and condensation was a sign it was in good working order.

Larry, my parts list is a book supplied by BFS which covers Solex, Zenith, Stromberg and Pierburg carburettors. It has  exploded diagrams of the carburettors and shows the parts that come in various kits. The spring you want is not in any kit.
I reckon a spring from a Chinese reject would do fine. While you're there I'd grab a handful.

I don't know if this is of any help. Maybe it could be downloaded to the technical section by one of our computer whizz kids.
Sorry, sideways again.

..and here's the Solex if of any use.
Sideways again.

Quote from: Alan Drover on Sep 18, 2023, 07:57 AMLarry, my parts list is a book supplied by BFS which covers Solex, Zenith, Stromberg and Pierburg carburettors. It has  exploded diagrams of the carburettors and shows the parts that come in various kits. The spring you want is not in any kit.
I reckon a spring from a Chinese reject would do fine. While you're there I'd grab a handful.

Thanks Alan.  I have contacted my source about the springs, but have as yet heard back.  I'll keep all y'all informed though.

To continue the story.  I have now pulled off the Chinese Zenith and put back my old Webber. The Webber definitely has less power - probably due to the smaller bore.
I am now on the hunt for an original Zenith to rebuild.

Should I be be buying an overhaul kit or a rebuild kit? Not really clear what the difference is
Thanks
Steve

Get a rebuild kit. If you can make out the photo I posted at #70, it shows what's in both kits.