Where to start? - 1971 250 w114 m130 zenith carbs - Page 11 - Mercedes-Benz Forum

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post #101 of 138 (permalink) Old 03-16-2015, 07:04 PM Thread Starter
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I don't know where I was in this thread, but I kept telling myself I would give the carbs another shot. So tonight I did.

The revelation that I had tonight (after realizing the accelerator pumps again seem to be stuck) is that the rear carb is sucking some air across the choke, while the front is not. I realized this while trying to start the car whole holding the chokes closed. I could feel the rear one sucking air by forcing the choke open, but the front isn't giving any pressure.

Right now I'm trying to make it run without the middle linkage. Hmm... Perhaps I should pull off the pedal linkage from the front carb.

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post #102 of 138 (permalink) Old 03-16-2015, 09:16 PM Thread Starter
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Pedal linkage didn't make any difference, but I think that I may have discovered that the small idle adjustment linkage needed some adjustment to allow some air through. I got by that problem and got the car running and revving.

I had messed with the high idle screw under the choke cover and had the car running at maybe 3000 rpm or something nuts. It took me a while to figure that one out.

Oh. At first the tank was out of gas. I put in maybe a gallon and burnt through it tonight. I learned how to quickly test if you are getting any fuel from the pump. Just unscrew the front fuel inlet and use the bump starter tool. The bump starter tool has actually made all this a lot easier. I guess it was a blessing that I fried that wire on the starter.

So I ran out if gas again after making tons of adjustments. But while adjusting things, I have to admit that I wasn't seeing a massive (or any?) effect from either:
1) the idle mixture screw. Even when I twisted it pretty close to closed, it didn't even begin to stumble. I think the exhaust was equally smokey under most circumstances. Perhaps I'm making adjustments too fast and need to slow down.
2) more importantly, the small idle adjustment linkage. I've adjusted both to the point where the linkage falls apart. I measured about 46 1/6th turns from as small as possible until it falls apart. I am now seeing very little effect when I do this. I wonder if I'm controlling the airflow with the chokes. Maybe that's something I'm doing wrong. I guess the only way that could happen is if the throttle plate is open (idle adjusted high) and choke is very tight (very much to the rich side). I wonder if I am doing that on the rear carb.

It was fun getting the car running again, and I am hoping that next time I put fuel in it and start it, it warms right up without issue. Then again, I'm wondering about that choke vs throttle on that back carb.

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post #103 of 138 (permalink) Old 03-16-2015, 10:38 PM
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Zeniths are initially difficult to master as they seem to have uniquely odd faults causing idling .runningand starting issues ,typically clogged idle jet tube,warpage of base due to a seized heat-riser flap and the top plate warpage due to overtightening of aircleaner screws.
Once setup correctly they work perfectly with the M130 and 110 engines.
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post #104 of 138 (permalink) Old 03-16-2015, 10:46 PM Thread Starter
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Originally Posted by adler View Post
Zeniths are initially difficult to master as they seem to have uniquely odd faults causing idling .runningand starting issues ,typically clogged idle jet tube,warpage of base due to a seized heat-riser flap and the top plate warpage due to overtightening of aircleaner screws.

Once setup correctly they work perfectly with the M130 and 110 engines.

Getting there. Worth understanding even if I just end up keeping my black 1972 250c. This blue 1970 250c is for parts and play, maybe even sell whole.

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post #105 of 138 (permalink) Old 03-17-2015, 02:40 AM
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Excellent learning project !
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post #106 of 138 (permalink) Old 03-17-2015, 06:02 AM
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Fonzi,

Are you using an air flow meter when you adjust the small turnbuckles on the rear of carbs? the ones you are twisting so much. I would guess not. you are at the point you need them. (First) step is to balance the carbs using the above. This will tell you if both carbs are sucking in the same amount of air and gas.

you need one of these
Empi 5746 VW Uni Syn Carb Synchronizer Weber Austin MG Jag Edelbrock 4025 | eBay

and them go to a plumbing supply house and get a rubber pipe reduction fitting that is big enough on one end to fit top of carbs and small on other end that air flow meter will sit on top.

Your idle mixture screws just set to about 2 - 2.5 turns out for now and leave them there.
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post #107 of 138 (permalink) Old 03-17-2015, 06:09 AM Thread Starter
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Thanks rumb. I can't tell how much either sucks. No tool. Time to buy, "shit or get off the pot" to say. (To clarify, I'm not on the pot. It's been many years since I've smoked that stuff, not that there's anything wrong with that.)
benzitch likes this.

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post #108 of 138 (permalink) Old 03-17-2015, 06:11 AM Thread Starter
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Quote:
Originally Posted by rumb View Post

To clarify, just one tool is needed. Correct? What if I was to buy two of them? Would that be better?

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post #109 of 138 (permalink) Old 03-17-2015, 06:48 AM
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just one is all you need, just move it between the two carbs
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post #110 of 138 (permalink) Old 03-17-2015, 06:59 AM Thread Starter
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just one is all you need, just move it between the two carbs

But will the process be any easier with two of them? At only $17 it seems worth it if there is ANY benefit or time savings at all. However, if they are calibrated differently, I guess information might be deceptive, requiring flip-flopping the tools.

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