Solex Carb Theory, Tuning

For my introductory thread, I'll start with the first challenge the little '64 has presented - a difficult carb.

I bought a rebuild kit from Kaiser-Willys and fixed the accel pump problems that were initially plaguing the motor. With no manual or assembly diagram, my adult son and I completed the job together (his first carb) and it drives much better. But it still has a big flat spot on the low end and I admit to being rather perplexed by the multiple jets, needles and funky choke setup on the Solex. I searched a couple of sites with little luck, until I stumbled on a VW-application YouTube that was helpful. I searched ever deeper until I found a couple of vids from India that contained great illustrations of the various circuits, but were extremely frustrating with difficult dialect.

Nonetheless, here is a link to the most helpful of them all. I hope it proves to be of value to those who follow:

 

Mine had the same dead spot on a good motor. I adjusted the accell pump and it took that out. It wasn’t doing much of anything prior.

 

Yes old school flat 4 vw ,s had solex stock. I've built over 100 of them, back in the 80s,90,s.
They are a great little carb. Not known for power, but for economy.(30+mpg in the 60s)
Most flat spots due to lean jetting and not enough squirt from acc pump.
U can also open up the squirt hole, but only slightly , couple thousands at a time.
Be sure itsquirts, as soon as u move the accelerator linkage, (the skinny pedal).

 

Yeah either my spring was too spungy or the arm was adjusted too far out stock. Either way, once I took it in a few full turns that dead spot vanished. That FHead ran very well once I was done.

 

Update #1:
A couple of weeks ago, I took the carb back off, disassembled and studied it some more. My son did most of the first rebuild himself, so I double-checked his work. I decided to put the original jets back in and start from a known baseline since the kit had some different part numbers in it. Reinstalled and idle/top end were solid, but still bogging despite accel pump working good. I power washed the engine compartment, the suspension, steering, and what propeller shaft joints I could reach. I drove around a little bit, then parked under a nice shade tree to check the timing. With the motor purring beautifully, I couldn't find the pulley notch. Then, the starter solenoid decided to flake out and 2 weeks went by.

Yesterday, I pulled the air cleaner, distributor and coil to get good access to the starter. NAPA had a solenoid and I got the thing cranking strong again. I also screwed a new set of plugs in and put the wires back as each plug was replaced. With no way to time the motor, I put the distributor back in with the rotor pointing where it was before coming out, and with the narrow (lower) adjuster slot in the middle of the range. After a couple of tries twisting the distributor, I got it to fire, but it wouldn't idle worth a crap and it was now missing. I locked the distributor's narrow slot bolt down, then moved to the longer slot toward the front of the motor to time it by ear. I advanced and retarded a few degrees each way until it would settle down somewhat. It's still idling too high - I'm guessing around 800+ rpm and missing. I'm pretty sure I have the idle screw in too far and have the transfer slot uncovered by the throttle plate. The carb will pull smoothly from high idle to high rpm with no flat spot, but the main jet is visibly discharging at high idle. I can't get the idle down far enough without the motor stalling now.

Sorry for the rambling post, but I just have to vent a little frustration until I can get my hands on the timing light again this week to get the dwell and advance set correctly.

 

Your miss is not due to the timing,u can play with the distributor to get the timing close,
The miss is something else, point gap or corrosion, condenser,wires or cap?
Since its benn wet, need to recheck everything!

 

Yeah, power washing is not a great thing for ignitions. And double-check you got the plug wires back in the correct order. Did you gap the new plugs?

"Most carb problems are electrical."

 

I found that my wires were not on the correct terminals and got that rectified. I pulled the distributor and confirmed the point gap at .020" with clean contacts, then reinstalled with #1 near TDC. All the wires are quiet in the dark with no arcing or stray voltage evident. I ran a compression test on the warm engine and the cylinders range from 135-145psi.

I fired the motor up and warmed it, but it's still missing. I can't get it to idle below about 1550 rpm and it's showing 32 degrees advance. Still running on the intermediate jet circuit with the idle stop screw nearly all the way in. If I unscrew it to seat the butterfly and run the idle circuit, it dies. Battery voltage is strong. I'm thinking the condenser may be on the fritz, with the coil a possibility after the pressure wash incident.

Updates to follow.

 

Vacuum leak?
Set that timing back to 5-10btdc, at idle. Bout 600rpm.

 

It WON'T idle at anywhere near a normal speed.

It really acts like a vacuum leak, but something that big would be easy to find. The previous owner said the motor had been rebuilt several years ago. I'm wondering if the oil pump was not meshed into the cam gear properly and the distributor is out of time. I've got to get it up on some stands and check the timing window on the flywheel vs the rotor position and set the distributor's point opening per the book.

 

Water in the carb?

 

After setting/cleaning points, I always pull a clean piece of business card through them several times. A tiny piece of crud or grease can cause misfiring,

 

While running at as low rpm as u can, pull 1 plug wire at a time and c if u can determin which cyl is missing?
The set up for this is to pull all wires, then place them back on plug, but don't snap them home.
Also, another test, while running, spray wd40, around carb, intake,vac hoses.
If it smooths out, or idles up, you've found the leak.
Do u have access to another carb to try?

 

If one of you gentlemen has a few moments to have a look at your distributor base, would you check the hold-down plate for orientation? I'm looking at the exploded assembly drawing in the manual and it shows the long slot pointing down and the short slot forward. This is the opposite of what my distributor looks like - leaving me very little adjustment to rotate the distributor to set initial timing. OTOH, the long slot forward seems ridiculously generous with adjustment range. I wonder if the previous builder flipped the plate and installed it incorrectly?

 

My dizzy only has a few deg of adjustment also, took me 3 trys to get it in correct position.
When installed correctly, you should be able, with a timing light to go from,0 deg Tdc to 15 deg btdc.
I tried book settings, 5btdc, but it runs much better at 10 deg btdc.
These engines are Way low compression, even with head and block milled, u won't detonate .
I Also put a slightly softer spring,on 1 side on the advance, under the point plate.
Keep us posted. Will eventually find the problem.
Hear is a pic if it helps?

 

So - are your distributors adjusted hard against the upper stop of the long (forward) slot, or some other orientation?