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Well, I decided to rebuild the Zeniths
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gregmasset
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PostPosted: Wed Jul 26, 2017 1:30 pm    Post subject: Well, I decided to rebuild the Zeniths Reply with quote

Couple years ago I went to drive my little car and she wouldn't run on the passenger side of the engine. Looking down the throat, I didn't see any fuel coming from the accelerator pump. I had the carbs rebuilt 20 years or so ago and lately have had a bear of a time with gas going bad in engines that don't get run often enough.
I ordered a pair of kits off Amazon this winter and then found Charlie White's (RIP Charlie) book on Zeniths. Last week I pulled one carb off and tore it down according to the book. Then I opened the "rebuild kit" and found that it contained nearly nothing and was not going to work. Found 356 Carb Rescue and got another set of kits sent. Then rebuilt/reassembled it, then did the other one. Finished it last night and went out to install (yep, out- wife let me rebuild 2 carbs on the kitchen counter!) Still was rough once it started so I went and checked, no fuel coming from the pump on passenger side. I pulled the banjo and stuck the fuel line into a bottle, then started the engine a 3rd time. After it ran for 8-10 seconds I shut it off and checked- no gas in the bottle.. Clogged fuel line? I pulled the line off the other carb, the fuel pump and unbolted the clip to the back of the shroud, snaked a welding rod in and wasn't sure if that helped. Sprayed some carb cleaner in and tilted the line to see if it would come through-- and the woven "flexy" line tore in half. Shoot. It was getting dark and one of my kids came through and obsconded with my flashlight so decided to call it a day.
The revelation that the carb(s) probably didn't need redone and most likely the fuel line was the problem all along came quickly. Why did I wait 3 years to do all this? 3 years of not driving my coupe.. Luckily, some of that time I spent driving Dad's roadster so not all bad, but thats still not the point.
I've decided to get all my cars running this summer and keep ethanol free fuel in them so I get to decide what to drive, not choose by what will run!
Hopefully I'll report back shortly with good news--
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saddlesore1
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PostPosted: Thu Jul 27, 2017 10:21 am    Post subject: Re: Well, I decided to rebuild the Zeniths Reply with quote

Over the years everyone has always said you have to drive them. Life gets busy and it becomes harder and harder to clean out all the stuff stack around it. You say tomorrow and tomorrow become a month, etc.
Ive discovered the hard way many time that "they MUST" be driven regularly, at least 1 time a month.
The fuel now days is crap. the Brake fluid retains water, Rubber hers hard, etc.
If you don't drive them plan on: rebuilding carbs, Rebuilding fuel pump, replacing the line that runs from the tunnel to the carbs, rebuilding the fuel pet cock and the dreaded rebuilding the brake wheel cylinders because the right wheel is frozen.
If you haven't rebuild the rear wheel cylinders your in for a real treat. If you thought rebuilding a carb is fun JUST WAIT.
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gregmasset
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PostPosted: Thu Jul 27, 2017 1:11 pm    Post subject: Re: Well, I decided to rebuild the Zeniths Reply with quote

Yeah, have That to look forward to..
Suspecting the fuel pump, isn't (pumping). Anybody know if all the fuel pumps are interchangeable? I see reference to the early and the late pump and I'm not certain which I have, but I do have a spare 912 engine so I'm thinking of yarding off the pump from it while I wait for the bits to rebuild this pump.
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saddlesore1
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PostPosted: Fri Jul 28, 2017 7:44 am    Post subject: Re: Well, I decided to rebuild the Zeniths Reply with quote

Just rebuild the one you have. Its easy. several small parts. make sure you have a clean workbench with a mat or towel.
Getting off is a pain in the ass because of location.
make sure you FILL the area where the cam rod hits the plunger lever with grease.
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Jon Schmid
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PostPosted: Fri Jul 28, 2017 1:04 pm    Post subject: Re: Well, I decided to rebuild the Zeniths Reply with quote

I recommend that if you are going to take the fuel pump apart, if it is not leaking from the top of the upper body dome that you leave it alone. It's real easy to overtighten the hold down bolt with bad results. Just remove the entire upper body from the diaphragm once the fuel banjo bolts are disconnected. Good luck.
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gregmasset
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PostPosted: Fri Jul 28, 2017 8:01 pm    Post subject: Re: Well, I decided to rebuild the Zeniths Reply with quote

Very good- thanks for the tips fellas.
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gregmasset
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PostPosted: Tue Aug 01, 2017 10:37 am    Post subject: Re: Well, I decided to rebuild the Zeniths Reply with quote

Took it around the block last night- sure felt good. It may've been my sons first ride in it, but definitely the first one he remembers.
I have some tuning yet to do, idles and free revs fine but stumbles badly under load. So happy to have it back in rotation.
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gregmasset
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PostPosted: Wed Aug 02, 2017 6:55 pm    Post subject: Re: Well, I decided to rebuild the Zeniths Reply with quote

I was thinking maybe the floats are set too low and it's running out of fuel when under a load-- but thinking back the "pre rebuild" had 2 washers under the float thing (can't recall the name, sorry) and now it has the 1 as recommended to start with. But, I think if I added another washer the float would be lower? I admit, I set the floats by standard rather than measuring because the kit didn't have the measuring angle. I have found the proper distance and do have a caliper if that's the way but it seems like maybe the float level aren't the problem. Any good Zenith (or universal) carb tuning advice?
Thanks Greg
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Starbucket
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PostPosted: Thu Aug 03, 2017 1:01 pm    Post subject: Re: Well, I decided to rebuild the Zeniths Reply with quote

Stumbling under load means "not en`uff accelerator shot of gas". Look down the bores as you open the throttle, you should see a stream of gas all the way till open. Adjust so the gas shoots AS SOON as the throttle is moved.
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roy mawbey
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PostPosted: Sun Aug 06, 2017 10:23 am    Post subject: Re: Well, I decided to rebuild the Zeniths Reply with quote

Gregg,

A few things to look at regarding your 32 NDIX carbs. Firstly just a point, you might already have attended to but, are you absolutely sure your plugs and leads and ignition are in perfect condition? You say it stumbles when on load, could be a duff plug, or lead connection. Are the points all okay. Best to double check these items first of all as your carbs seem to be behaving them selves on idle and not under load conditions.

Second thing the needle valve located in the top portion of the carb that controls the flow of petrol ( sorry gas ) into the float bowls does have the one washer probably 1.00 mm thick. Inserting more washers does change the float height in the bowls. Adding another washer of 1.00 mm thickness will alter the height by about 4mm.

Of course you need the height from the top of the gas you can see to the top of the carb bowl to be correct at 18.5mm plus or minus 1.00mm. Can be checked with the end of a vernier or some have a special tool that screws into the carbs fuel line. This item makes that job much easier and will show the level in a glass tube.

But... I really wonder if that is the cause. If it idles well and is stable then if you immediately drive slowly in first and second gear straight ahead does it stumble? If you keep the rpm to a low value on driving does it stumble?

If that that's not the case then the injection quantities from the two small diameter pipes you can see if the looking into the venturi should be checked. If you turn off the engine take off the air cleaners and looking down into the venturi of the carb depress the throttle levers on the carbs down to the stop The pipes should squirt fuel on each carb. If there is a blockage or just a dribble. The quantity of fuel delivered needs checking.

Two full strokes of the throttle lever equates to 0.3 cc. A medical syringe can be used to check that value and a receptacle made up to catch the fuel from the pipes.

Maybe under load the extra fuel needed from these pipes when you need to overtake might not be there as required.

Look on internet for tuning or maintenance on Zenith 32 NDIX for in depth info. Just some thoughts from my end. Had similar problems over the past 48 years driving mine.

Roy
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Roy
RHD356A super75 106954
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gregmasset
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PostPosted: Fri Aug 11, 2017 9:39 pm    Post subject: Re: Well, I decided to rebuild the Zeniths Reply with quote

Thank you Roy, I've been on holiday for the last few days, but I'll bring it out over the next couple days and do more checking.
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