Solex carb main fuel jet


Ken Chambers

Hi all,

Here's some info on our Solex carb main fuel jets:

I removed the main fuel jets from two of my Amphi Solex PSEI carbs and found the
jet on one carb is a 110 while the other is a
115. BTW, when I say main jet, I'm referring to item 43, Main jet, in the
Amphicar Parts Manual on Plate 07. The size is stamped
on the jet and refers to the metric drill size. For example, a 110 jet has a
1.10mm diameter hole.

The jet is located in the bottom of the float bowl. It can be accessed by
removing the 7/16 inch hex plug near the front of the
carb. It's possible to remove the jet without removing the carb, but only if
you're very careful and possess the right tool.
You'll need a starter screw driver - a split blade type seems to work best.
You'll need to remove the plug and crack the jet loose
using a standard screwdriver. Then reach in with the starter screwdriver,
expand the blades and carefully remove the jet. If the
jet falls off in the bowl, you'll then have to remove the carb and shake it out
of the access hole.

The jets are made in the following sizes, with the 110 being the smallest
available, from what a distributor told me:
110 111 129 405A
112.5 111 129 405B
115 111 129 405C
120 111 129 405D
122.5 056 129 405A
larger sizes available, but those are for larger displacement engines

Those are VW part numbers (early VWs used Solex PICT model carbs with the same
jets), however, they're no longer available at the
dealer parts windows. Old VW after market shops carry them in the range of $5
each. Another source is The Carburetor Refactory in
Richmond, CA. Telephone number 510-237-1277. About $8 there, but they'll ship.
BTW, this place also rebuilds old Solex carbs
including rebushing the throttle shafts. I haven't used their services other
than having purchased a Solex rebuild kit.

Getting back to my Amphi, I felt that the engine was burning somewhat rich even
at near sea level. This was empirically derived
from the fact that I smelled a lot like exhaust fumes after driving a short
while. This carb had the 115 jet in it, so I swapped
it to the 110 jet. Doing the math, the area of a 110 hole is about 10 percent
smaller than the area of a 115 hole. I don't know
if that directly correlates to 10 percent less fuel flow. The car runs
perfectly fine with the smaller jet. In fact, I think it
runs even better. It easily maintains 70 mph, even 75 if I keep it floored. I
believe the fuel to air mixture is more correct now
owing to the fact that I don't smell as much from exhaust after driving it.

The fact that our 1147cc engines are probably the smallest displacement engines
mated with this Solex carb, it makes sense that the
smallest jet is the correct one. If you operate your Amphicar primarily at high
altitudes, you may want an even smaller jet.
Unfortunately, you'll have to silver solder and redrill your own. When I went
Amphi camping recently at a 6500' elevation lake the
engine was running so rich it was choking on fuel as evidenced by the black
sooty tail pipe, but that was with the 115 jet.

I don't know why I had two different size jets on my two carbs, unless someone
had rejetted one of them somewhere along the way.
It would be interesting to know what size jets were originally supplied.

Hope this is of interest.

Ken Chambers, CA
64 Amphi


I recently rebuilt the Carb on my 1964 using the rebuild kit available from
Hugh. After I re-installed the Carb in my engine, it began to run rich and
blow a little black smoke out of the exhaust. I pulled it back out and found
the jet that came with the rebuild kit was larger in diameter. I changed it
out with the original one and the engine once again ran great. My Carb is
different than the ones I have seen on other cars. (smaller) I am wondering
if maybe the earlier cars used a smaller Carb on them.

Dave VanRens
1964 Red

Moses Scott Civ 22 LG

There is also an air jet in the top of the carb as well. I installed a
smaller fuel jet in the bowl and a larger air jet. Leaning the engine
causes it to run hotter, so watch that temp gauge!
I don't have any of the details as to the numbers of the jets. I ordered
the next smaller fuel and next bigger air jets from Gordon's.

Scott Moses