Solex Carb Question

There is some backstory here, I apologise in advanced to those who read the whole ordeal, but appreciate any insight.

I bought the Jeep as a running wreck, it did start and move (a bit) under its own power. I ended up tearing it all apart and pretty much rebuilding everything. So I don't have a good point of reference for what a 'well running' F134 is capable of. It turned out the YF Carb was as much of a wreck as the rest of the jeep, it was missing all the internal springs and at some point random springs were fitted, including the annoying spring that holds the metering rod in the jet. A rebuild kit was tossed into the Carb and it idled fine, but everything else was a complete disaster. I shelved the YF and bought a solex.

To the credit of the Solex, it bolted on and just ran. The Jeep didn't seem to have a lot of power at the top end, it was a bit of a struggle to get the jeep up to 90 km/h (55) but it would run. The overdrive at 55 was a bit hit or miss, it really lugged the motor and I often found I didn't have the power to run O/D and just left it in 3rd. When I resealed the engine, I did note that the rebuild tag on it was from 71 or there abouts, but the motor had been sleeved and the sleeves still had crosshatch on them, I chalked up the bad top end performance to engine wear.

This spring, the Solex didn't want to start and run well, I figured I was rebuilding a carb anyways so I grabbed the original YF and another Jeep YF I had since acquired and built one good YF carb. I tossed that on the jeep and got it running (eventually). I fought needles, but eventually got it to only drip occasionally. This was the best the Jeep has ever run (It should be noted this lasted about 3 days), the jeep easily pulled up to 100Km/h (60 MPG) and when engaging OD at these speeds didn't lug or bog. Great top end power. Then the carb started pissing fuel (again). A fuel regulator was added and it was either pissing fuel everywhere or starved.

The Solex was cleaned and bolted back up. I will note that the idle (600 RPM)on the solex is a lot smoother and it never stalls, with the carter (800 RPM idle) it was set to idle higher, but still on occasion would stall at idle while at a stop sign or light. I haven't shelved the carter for good, I will probably order a Daytona Carb kit with the improved needle float and see if that helps at all, but in the meantime I want to figure out the Solex issues.

A solex tuning guide seems to indicate that lack of a top end can be caused by too small of a main jet or too large of an air jet. As well, not being able to climb could be a too small of a main jet.

It feels like my next step is to bump the main jet up and possibly run a smaller air jet, I'm just wondering if anybody has tried tuning a Solex for the F134. If so, where did you land on Jet sizes? I certainly don't want to blaze this trail if somebody else has already done it.

I did want to add, I did check the obvious, the Solex is opening completely when the pedal is fully depressed.

1960 CJ5
F134
5.38
30 inch tire
Warn OD

 

I can't speak to whether changing jets on the Solex is in order because the way I tune a Solex is to remove it and replace it with a Carter YF

My CJ5 is a standard with same engine and axle gearing, and I think 55 and 60 MPH is pushing it with a F134 Jeep and 5.38 axles. A carburetor "pissing" gas is an indication of improper set up. I suspect float adjustment is not correct.

 

I'm aware that some YF kits include an incorrect solid needle (too long), I used both a good original needle and a new (correct length) one from the kit. I hunted down a 3 piece needle (with the spring) that was originally spec'd for willys jeeps. That needle was the best, but didn't last a week before leaking. I'm aware that the 3 piece and the solid needle have different specs in regards to float height, the right spec was applied to the correct needle. I had two floats (both brass) , neither had any fluid in them and tested OK for leaks. Even with a pressure regulator, the carb still wouldn't seal. There is a fuel filter just before the carb and when I dismantled the carb to inspect the needle seat there was never any obvious debris in it.

Its entirely possible that I'm simply working from worn out cores that will never be right, but right now I'm putting the effort into the Solex as it seems to be the best path forward.

I'm hoping to eventually order the Daytona carb kit and see if there needle float is indeed the solution to the problem, but being in the great white north shipping is always an issue.

 

I have the same setup. F134, 5.38, my tires are a bit smaller at 28".
Running out of steam around 55-60 is completely normal with 5.38's and the f-134. The "comfortable redline" is around 3000-3200 rpm which is about 55-60 mph anyway so unless you want to throw a rod, I wouldn't spin the engine up higher than that with your current gearing. This is assuming you don't have a tach. which I don't haha.

My solex leaks fuel as well unless it gets exactly 1.5 PSI using a regulator. Take the solex apart and clean it out real good. I has some crap in mine out of the box when new. You might just have something stuck in the main jet and a cleaning is the cheapest fix, if that's the problem.
If you let it sit for more than a few weeks, it'll need a cleaning anyway. that's the nature of carbs. Maybe use some sta-bil next time its gonna sit for a while to help.

For the top end power... you might try also checking your timing. If the jeep sat for a while, throwing on a new cap and condenser will take that out of the equation too. Check your spark plugs and wires. make sure everything is working correctly on that topic. Make sure all 4 pistons have good compression. This stuff will all add up on the top end and leech the feeling of power. Check your air filter and make sure its clean and free flowing. check for exhaust leaks.

Just a general check list of stuff to go through. before changing the jetting of the carb. The solex's are super simple and generally set up to run correctly out of the box. They even discourage messing with the settings beyond the idle mixture in the instructions.
Unless you're at a high altitude or something, you wont need to rejet to make em run right.

 

Quick Update

I spent more time digging about and found what looks like official or at least official enough documentation that I can use it as a starting point.



I'll try and document what size jets I have installed in my Solex, This should offer a starting point for any modifications, I don't drive the Jeep to really care about the 'Economy' settings, so I think I'll start with the 'Regular' settings as a baseline.

The Air Correction Jet may be the tough one, may have to solder it shut and redrill a smaller hole.

More to come.

 

Are you also aware that for the correct YF needle valve Jeep application, the orifice is a smaller opening?

This reduces flooding on steep or rough terrain, since the input pressure from the fuel pump puts reduced force on the float.

Also the fuel pressure must not be higher than Jeep specified, under 3psi IIRC.

It matters.

 

just curious…is this specific to solex carbs? I’ve let mine with a Rochester carb set for a month and a half before and it started right up. But I only use ethanol free gas.

 

I think its more the nature of the gas. Could be the ethanol, could be old gas. whatever the case.

 

Just wanted to follow up on the Solex Jet surgery.

The main jet was stamped 127.5 and the air jet was stamped 190. It looks like the Solex was equipped with the 'Economy' settings.

The cheap off brand dirtbike jets (5mm X 0.75) fit nicely in place for the main jet. I ended up drilling the Main Jet out to .055 (1.397 mm)

The air jet is larger, I think (6mm X 1.0) but I didn't buy any off brand jets in that thread size, so I ended up using some plumbing solder to close the hole and re-drilled it out to 0.060 (1.524mm).

The results which are all very subjective:

It seemed to stumble a bit under acceleration when cold, but once the up to temp (< 2 mins) the stumble disappeared entirely.

The performance seems pretty much the same as before, except for one notable exception. The top speed is still between 80KM-90KM (50mph-55mph) with the solex, but when when in third gear and I engage the overdrive the engine doesn't bog or lug when I'm driving into the wind or up small hills in the road. This is a huge benefit in my mind, previously with the Economy Solex setup the overdrive use was very limited at top speed. I was having to drop in and out of overdrive constantly to adjust for headwinds or small hills.

I'm wondering if I could find a couple more 100 RPMs at the top end if I switched (what I suspect is) the 26mm choke tube for a 28mm one. I would assume standard Solex parts would fit the carb, but I'm very happy with the improvements I have so far and I'm probably not going to chase the choke tube upgrade.

I'm going to drive it for a bit, if I understand how the Air Jet works, the carb may be a bit rich at high speeds, if i see any evidence of that, I will probably drill out the air jet a hair bigger.

 

I did confirm that the throttle link is allowing the carb to fully open. I'm pleased with the top speed, back of the napkin math would indicate that the engine is spinning about 3300 rpm, I think with the Carter YF, I was able to achieve approximately 60 mph (Engine RPM about 3600). I'm not sure the F134 is really capable of much more then that.

 

Probably not. And speaking for myself, I hate to run an F-head at anything over 50mph.

 

IMHO, that is not an "achievement" to strive for.

The early F-head Jeeps are excellent for crawling and climbing, but I think it is an unfortunate misapprehension to focus on "improving" their power/speed. Lipstick on a pig. They were never meant to be highway vehicles.

 

Me-thinks you've missed the point entirely. I found the Solex carb as provided did not provide enough 'power' to run the Jeep at cruising speed while in Overdrive. As I only had a single point of data to work from, I mistakenly assumed this was a natural limitation of the vehicle or related to age and wear. The brief period of time the YF ran OK, demonstrated that the limitation was likely related to fuel and in particular how the Solex is setup.

I'm not looking to improve the performance of the F134 beyond its original design, I'm merely working to improve the performance of the Solex carb to that of the YF.

I've tried to describe my issues, include details of what my setup is and provide a conclusion. My thought process was to merely add my single data point to the already large collection of knowledge available here.

 

In that case I'd suggest just finding a good YF. They don't "p!ss" fuel unless there is a distinct problem, likely easily fixed.

 

If you're open to someone else rebuilding the yf for you…. I know the jeepsterman and a couple other places do “show quality” rebuilds of em for only a couple hundred bux.

the Solex has been a solid performer in my experience. People are usually in either of the two camps about carter vs Solex but it seems as if you favor how the yf works for your build. Might be worth investing in just bringing it back to working standard instead of dumping money into the Solex, hoping it’ll become a carter.

 

Alright folks, let's remember this thread is about the Solex and any "help" regarding the use of a YF is off topic.

What we need to focus on here is Solex tuning and baseline performance of the f-134.

I can assure you you can hit 85mph (down a very steep grade) with an F-134 and it is sketch and will likely lead to elongated big ends on the rods. I have seen a block of an f-134 that has thrown a rod and I have also driven 55mph on the interstate with and without overdrive for days. (Not recommended)
If you are dana25 front typically you have a t-90a with 5.38s and it was made in a time where 55mph tops for any length of time was the legal limit. With a t-90c and 4.27s or the 5.38s and an overdrive you can go a little faster on the flats with 28-30" tires and a healthy motor but 32s will actually be slower in overdrive and faster in drive. That was with several carbs and a healthy motor.

Once you get the carburetor sorted (wideband o2 and vacuum guage would help) i'ld see about your end goal expectations.

A F-134 is a good motor it just isn't very fast and requires a lot of TLC, that's just normal for it's era. If you decide the 134 is good but you want a little margin than you can sink a lot of money into upgrades and get a little bit of performance gain or thought not required drivability with modern tbi options but if you are not happy with it now you will waste a lot of money trying to get an oxen to win a horse show.

Should you not be satisfied with the 1960 pace the typical motors swapped in front of the t-90 are the 87-2010's chevy 4.3, the Buick 225 which is older and harder to find but technically the "proper" candidate, the Ford 2.3l or 90's ranger 2.5l, then there is some charted but minimal explored territory with Buick 3.8l, chevy 4cyls, mercruiser 4cyl, Ford and chevy v8s, and I'm sure you could get an ecoboost to work but that would be a financial mistake.

I'ld also agree that sending the YF to a specialty shop is likely a good idea. The rebuild kits cover way too many years and motors to be good for any one in particular.