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ZS Question for 76 1500 midget

Tipsy

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Yesterday I topped off my Zenith Stromburg carb with 20w50 oil and it made it hesitate and chug a bit. So I got as much of it out and replaced it with some household oil which I'm thinking is too thin? Probably should switch to a straight 20 or 30 weight. But here's my question, It started and ran fine and I headed to the gas station to fill up my tank. Only a mile or two from home. After I filled it up it would not start for the longest time. This has not happened before. Is it because of the too thin oil? Or did I maybe just flood it?
Thanks!
Jeff
 

JPSmit

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Most likely you flooded it. Oil in the damper will affect acceleration but shouldn't impact starting. BTW, automatic transmission fluid seems to be a sweet spot for viscousity.
 

Morris

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I had a lot of issues with the float getting stuck on my ZS. This problem would typically manifest itself after a short drive.... which is probably just coincidental... but it's probably worth checking out.

Also... a worn or poorly seated float needle can make for very hard starts.

Annnnnd.... I think the ZS is not so easy to flood as it does not have an accelerator pump. But I am frequently wrong.

Regardless, probably has nothing to do with the damper oil.
 
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Tipsy

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Found a large three part article about rebuilding ZS carbs that I researched when I rebuilt mine last year and it says "if there is no oil (in the damper)the engine will start with difficulty and will not accelerate quickly". I took this as possibly meaning that a very thin oil, which could act like no oil at all, might make it difficult to start. So this morning I replaced the very thin oil I had put in the day before and replaced it with 30w I had used in the past as I did not have any ATF handy. Seems ok for now but I'm gonna guess that I probably flooded it. Normally I don't need to touch the pedal when it's been started and warmed up in the summer but this time I accidentally hit the pedal before starting it. So it's possible I flooded it that way. yes, no acc. pump but still possible to over do it.
 

dklawson

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Everyone has their own preference for what weight oil to use in the damper. It is a discussion I cannot really add to. However, for future reference and spares to carry in the boot, 3-In-1 oil is convenient. The "blue" bottle is 20W, the "red" bottle is 30W.
 

nomad

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On SU's I seem to remember reading somewhere that if you are having a lean miss on acceleration that it may be helped by using heavier oil in the dash pots. Want quicker pickup use thinner.

Never did a comparison.

Kurt.
 

StarkM

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On the 1500 with water choke (automatic choke) it is very hard to flood. As Morris said, these do not have an accelerator pump. The starting procedure for these 1500's and MGB's with the auto choke is this: Depress the accelerator to the floor once, then crank engine. By doing so you are setting the choke (essentially pulling the choke cable out), as the engine warms up, the coolant flows through the choke body warming the spring that gradually reducing the amount of choke until it is completely off. Pumping the pedal causes the choke to be set and released, it does not spray gasoline into the carb.

As for the dashpot oil, the official weight is SAE 20W/50. We do sell dashpot oil, which is SAE 20, however, I too have used ATF with success.
 

reddsprite

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I use motorcycle fork oil (20 wt) and it seems to work fine on my twin SU HS2's-I have never had any problems with this setup
 
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Tipsy

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Thanks for all the input! Mine is a manual choke which I have not had since my first car back in the 70's hen I was a teen. But I only drive the midget in the summer as it has no heater. And I rarely choke the carb. It always starts cold with a pump of the pedal one time and usually no pedal needed after short warm up. So I believe I should not have pumped it at the gas station but maybe i'm wrong? If there is no accelerator pump then what introduces the gas to the carb? I'll have to go back and read the article again as it explains the science of the ZS carb.
 

bthompson

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If you have a manual choke, then pumping the pedal before cranking does jack-diddly-nothing. The gas is introduced purely by venturi under the cylinder and past the needle. The choke is nothing but a progressive air bleed in front of the butterfly, which reduces the vacuum over the piston. The piston sits lower, the orifice is smaller, the air flows faster past the needle and sucks more gas through. Voila. That's why with a ZS it's crucial to have a perfect vacuum...any leak will drive the system richer. You may have a combination of worn needle and manifold leak...it'll run rich enough to get ya started, but when the engine heats up and you try to restart, it's too much juice and floods out. Been there!
 
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Tipsy

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Thanks Bill! It's beginning to make a bit more sense now. the needle is brand new recently with the carb rebuild. Manifold leak is another story. New exhaust/intake manifold gasket at carb rebuild time as well. But because of location of studs couldn't torque the nuts properly. Did my best but it's possible it could he a leak there. Have not checked head bolts if that's where you're talking about vacuum leak.
Jeff
 

JPSmit

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Tipsy said:
Thanks Bill! It's beginning to make a bit more sense now. the needle is brand new recently with the carb rebuild. Manifold leak is another story. New exhaust/intake manifold gasket at carb rebuild time as well. But because of location of studs couldn't torque the nuts properly. Did my best but it's possible it could he a leak there. Have not checked head bolts if that's where you're talking about vacuum leak.
Jeff

Jeff, I also had an issue where my manifold needed re-tightening - took awhile to figure that out.

Also, while you really can't torque the bottom studs, everyone I know with a 1500 has their special bent wrench to tighten it. Have you made yours yet? I can post a pic of mine though every shape is unique.
 
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Tipsy

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JP! No I have not bent one. This is my first time with the manifold. Please show a pic!
Thanks!
Jeff
 

JPSmit

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Tipsy said:
JP! No I have not bent one. This is my first time with the manifold. Please show a pic!
Thanks!
Jeff

this is mine - Pic two is how I get torque on it.

2012-08-18131556640x480.jpg


2012-08-18131659640x480.jpg
 
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Tipsy

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JP Thanks! I knew I needed something with a bend in it. Can I get enough heat with a MAPP gas torch or do I need something hotter? I'll have to experiment.
Thanks again everybody.
 

JPSmit

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Tipsy said:
JP Thanks! I knew I needed something with a bend in it. Can I get enough heat with a MAPP gas torch or do I need something hotter? I'll have to experiment.
Thanks again everybody.

I just bent that one in a vice. Otherwise bring it to a muffler shop, they'll be happy to help!
 
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Tipsy

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OK So now I'm beginning to wonder if this issue could be the result of my fuel pump? Today I went to the hardware store and when I came back out 5 minutes later I had the no start problem again. It starts just fine the first time at home in my garage, then I go somewhere on a short trip and when I come back out to leave it wont start. I recently replaced my extremely noisy unknown name brand fuel pump with a Mr. Gasket import car pump. Much quieter and seems to handle everything fine except maybe this. I know some folks on this forum are saying the Mr. Gasket pump is junk and others say it's just fine. Everyone has their personal brand preference. This was what was available locally for me so I thought I would take a chance on it. Maybe I should change my filter that is down below the carb? There is another filter before the pump as well. The filter before the carb is a couple years old and I don't get much mileage on it. But it was all functioning well before the pump changeover. JUST NOISY! And the old pump is gone to the trash weeks ago so no chance of putting it back on. As I said before, the carb was just rebuilt last fall with a new needle too.
Anybody got any ideas?
 

Morris

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It could be your pump overdriving your float... but I still think you should double check the needle, the float and the float level. Lowering the float level could do the trick.

Next time it is difficult to sart, pull the air filter and stick your finger in the throttle body and see if it comes back wet with fuel. This won't sort out whether it's the pump or the float, but it will tell you that flooding is the problem. After all 90% of all carb problems are ignition problems. :wink:
 

JPSmit

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I think it unlikely to be the pump. Either pumps work or they don't. It could be a clog but they typically happen while driving and clear up while parked as things fall to the floor. Do change your filters as they are cheap! What colour are your plugs? Could you be running very rich and soaking them?
 
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