a fun day with my zenith carburetor

bmw art car

bmw art car

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I spent the better half of the day trying to figure out why i can't seem to get the carbs balanced and running half way descent.

i did find out that the rear carb (the one close to the firewall) had a stuck 2.nd barrel butterfly. i got it unstuck finally.
but i also noticed that the idle lever doesn't go down as far as the lever on the front carb.
and the idle mix screw can be tuned in at least half way before it even moves anything. that seems wrong compared to the other carb

so with all the stuff and trying the closest i got to 700-900rpm idle speed is 1500 rpm. its either that or the car will run so crappy, that one isn't sure whether it's a straight six or a tractor.

i wonder if i shouldn't get some weber i can get the manifold and two of the triple weber from my friend.

they don't need to be hooked to the coolings lines , right?
i don't like that part anyway. good things always seem to be the least complex devices.
is a new weber set up the way to go? or try to find some rebuild zenith
and hope to spend some friday afternoon driving the car instead of getting asphyxiated .
 
Idle? What Idle? The Zenith of carbs!

That's not an idle.....

The throttle disk has to close or be very close to closed. So yes,there must be something wrong.

Take the throttle rod linkage off the offensive carb. Did the linkage release?

Is the plastic linkage different in length from the good carb? This part can hold a throttle plate open.

Bad cam ( inside the choke housing)or in backwards, twisted shaft ( doubtful), return spring not set in the little groove, stuck shaft, disc not centered, disc/ screws loose, somebody put it in backwards ( the i.d. numbers on the disc go down).

Since the secondary was stuck, spray/oil the crap out of the primary and try to get it to close while watching the cam ( the curved linkage part that releases/activates the secondary with the little roller.) If that doesn't work; take off the choke cover and look for the other fast idle cam and manually close it if it isn't.

So let's assume we want to fix this since it's cheaper to fix what you have most times. New webers- $700 New triples- $1300. And you have to dial them in and linkages, , after learning a few new german cursewords, etc.

Idle- a seperate circuit which means it can run all by itself ( almost). For the carb that's seems the worst- take the solenoid off and bench test it to make sure it opens and closes with 12v. If that's working and no gas is coming at idle, you have to clean the circuit and jets. It's the tiny needle one. Or take your chances with an air line and blow it out where the idle solenoid screws in if you're feeling lucky.

A picture of the bad carb/ screw might help.
 
Don't give up on the Zeniths so quickly, I've had webers on a previous coupe and having lived and breathed (literally) my Zenith rebuilds the last 2 months I finally have them running right and they're great. Just takes some patience to understand the intracacies of the parts and how to set them up correctly. There are a few recent posts on this, and 61porsche helped me work through what i was starting to think was a dead end task.
 
wow... great responses...
first @ porsche
when i noticed the linkage not going down the way it should i disconnected the plastic rod. the rear linkage connection was off already. i had a peak inside the choke housing... what a nightmare to get off... especially since it's the rear carburetor... replaced the screws with 7mm hex bolts to make things a tiny bit easier... inside it looked all ok. i sprayed a lot of catalyst into the second barrel.
plastic linkage is the same length as the other carb. i measured them to spec.
i'll take a photo now

61porsche said:
That's not an idle.....

The throttle disk has to close or be very close to closed. So yes,there must be something wrong.

Take the throttle rod linkage off the offensive carb. Did the linkage release?

Is the plastic linkage different in length from the good carb? This part can hold a throttle plate open.

Bad cam ( inside the choke housing)or in backwards, twisted shaft ( doubtful), return spring not set in the little groove, stuck shaft, disc not centered, disc/ screws loose, somebody put it in backwards ( the i.d. numbers on the disc go down).

Since the secondary was stuck, spray/oil the crap out of the primary and try to get it to close while watching the cam ( the curved linkage part that releases/activates the secondary with the little roller.) If that doesn't work; take off the choke cover and look for the other fast idle cam and manually close it if it isn't.

So let's assume we want to fix this since it's cheaper to fix what you have most times. New webers- $700 New triples- $1300. And you have to dial them in and linkages, , after learning a few new german cursewords, etc.

Idle- a seperate circuit which means it can run all by itself ( almost). For the carb that's seems the worst- take the solenoid off and bench test it to make sure it opens and closes with 12v. If that's working and no gas is coming at idle, you have to clean the circuit and jets. It's the tiny needle one. Or take your chances with an air line and blow it out where the idle solenoid screws in if you're feeling lucky.

A picture of the bad carb/ screw might help.
Click to expand...

Stevehose said:
Don't give up on the Zeniths so quickly, I've had webers on a previous coupe and having lived and breathed (literally) my Zenith rebuilds the last 2 months I finally have them running right and they're great. Just takes some patience to understand the intracacies of the parts and how to set them up correctly. There are a few recent posts on this, and 61porsche helped me work through what i was starting to think was a dead end task.
Click to expand...
 
of course now that i went out there to take photo's
the linkgages and cams look just the same.
but before i sprayed the linkage with something called 'blaster'
and i also sprayed plenty into the second barrel just in case...
the front cams
screw003.jpg

and the rear cams
screw004.jpg
 
PB Blaster

Spray it again. Spray the outside area where the throttle plate screw is and the spring below it. take a screw driver and see if the spring is in tension or loose. ( tension is good.) Get some white grease and lube the roller on the linkage. Check the accelerator pump linkage by moving it up and letting it fall in case it's hung up. ( good time to check the squirters too)

Secondary hung up before- take the top off the vacumn box, inside is a spring. Count the coils. Should be 8 for you; 10 for 3.0. ( Easy way to get your secondaries to open quicker too!) No one has asked me about this yet.... hotrodders.. remember those holleys.:)

When you start it again and after it warms up, if it's still idling high: turn it off, ( let it cool down a bit) hold the throttle wide open, find the secret high idle choke screw and turn it out a half turn on both carbs for grins.

On the primary throttle screws- counterclockwise till there's no movement on the linkage; then tighten down until the just barely start to move then maybe a 1/8 turn more to start. Both carbs.
 
Throttle plate screws

On the second picture- make certain the linkage is not being fouled ( touching/ rubbing) by the throttle plate screw and the screw is not bent.

Looks mighty close.
 
61porsche said:
On the second picture- make certain the linkage is not being fouled ( touching/ rubbing) by the throttle plate screw and the screw is not bent.

Looks mighty close.
Click to expand...

Just as you said, the screw was mighty close.
so, I fixed that...
Now the car idles decently, however, when i try to rev her a little,
she doing something not too nice.
I uploaded a video to explain it better...
(also there is a bit of a high pitch metalic hammering noise. Could the be a valve clearance issue?)
http://www.youtube.com/watch?v=WFx2z7eOsPE
 
Last edited:
The sounds of Mettalica

Some valve noise- adjust.

But, pull the cover and look very closely at where the chain and the timing cover are closest for bright shiney wear marks. What happens sometimes is the timing chain adjuster is at it's end of travel or the end of it gets grooved and the chain wants to move around a bit. Pull it, look it over, measure, clean it or just replace the thing. The other check is to stick a skinny screwdriver down along side the chain, pry a bit, to guage how much streach has occured. If you've been back firing a lot- the adjuster can close up a little internal to it's bore.

Check your timing again too. Might want to try backing off a bit.

What's the vacum lines that are running through the linkages hooked to? Try to reroute or ty wrap out of the way.

You need more clamps on the gas lines- T's, etc. Safety pls.

Check your linkages again- looked like the front carb linkage moved before the back a little.:-D
 
Zenith linkage

Yes, on the plastic. Be sure to measure them in the correct orientation. a 1/4 turn can mess it up.

But , also push down on each of the linkages to see if the return spring is a little weak or the throttle rod is effecting one carb faster or sooner.

On the long rod to both carbs, you want just a little lateral play. Then as the manual says, the snap linkages have to fit just right without moving anything. You should be able to put them ( snap) on by hand and not by pliers, etc. I grease mine a little.

The other thing is wear- you can take a little slack up. But if it's appreciable, better to get new ones if you're going to go for it.

One more thing on the linkage- check the length of the long rod against the manual and make sure you have wide open throttle. I've seen them slightly bent, the spring near the motor mount/ bushing needs cleaned/ greased. What you're shooting for is a consistant return to a predictable or repeatable idle.

Looks like it's doing better though and that's very good.

Time to sync. How's you vacumn readings?
 
I saw both of my plastic adjusters have cracks :(
I would have to replace them pretty soon... but where can i get them from?
 
Cracked plastic linkage

Are you sure they run through? Sometimes it's just superficial. Maybe a picture?

I think I saw them on Jaymic's site. I don't recall if it was the Solex spares or the E9.

I've got at least one used.
 
61porsche said:
Are you sure they run through? Sometimes it's just superficial. Maybe a picture?

I think I saw them on Jaymic's site. I don't recall if it was the Solex spares or the E9.

I've got at least one used.
Click to expand...

Yes, the cracks go right through. They have been fixed with shrink tubing, as it apears
and the two pieces are only secured by the tubing design :(
 
Plastic (cracked) Fantastic zeniths

Wow! Both ends both carbs? Something's stuck or was. Don't overlook Mercedes carb parts.

You're welcome to the one I have if that helps.:)
 
Two words - fuel injection

Sorry, couldn't help myself..thinking back to when I had those Zeniths and, on a good day, I felt like the car was the master and I was the slave. However, I do miss the carb/induction sound...just don't have that any more with L-jet and Motronic 1.3. Good luck!
 
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