I have been fooling around with Solex jets and would like some more opinions
Engine is a 68 U20, B-cam, Solex manifold with all vacuum ports tied
together, late model Mikuni 44PHH carbs (single wingnut jet cover, without
externally adjustable float). My current carb configuration is:
34mm chokes, 135 main, 140 air, 60 pilot, 35 accel pump nozzles.Float level
is set 0.849" from jet mounting surface (equiv to 24mm above carb
centerline).
I have experimented with the following:
-- 135 mains, 190 airs. Results loses power at about 6000 rpm, confirmed by
going very lean (0.04v) on the O2 sensor.
-- 140 mains, 200 airs. Results very similar to above, but lean cutout at
slightly higher rpm, I suspect this config will hurt gas mileage too.
-- With 55 pilot jets (with any of the above main/air jets) I get a slight
lean surge at light throttle up to 3500 rpm. I also found that setting the
float level per the manual with a 12mm gauge ( I used a 31/64" drill)
between the float and float cover resulting in low float level. I now remove
a jet block and measure the fuel level using a digital caliper depth gauge
( 0.849" below jet mounting surface), similar to the approach of using the
NLA Mikuni glass gauge shown in the Roadster manual.
-- With the 135 mains, 140 airs I get good power all the way to redline, but
appears rich on the O2 sensor (~0.92v)
-- The 60 pilot jets give smooth transition from idle through redline and
no lean surge.
I still get a bog when I stab the throttle below 3500 rpm, I assume the
accel pump nozzle is too small. I am running in the top hole (closest to the
pump body) and the pump stroke is 7.5 mm per the Mikuni manual. I am
considering going to a 45 or 50 accel pump nozzle. Will Campbell is running
a 60 long (long is for the 40 PHH carbs) with good result in his late 44
PHH, 34mm, B-cam config. The long jets with the 34 mm chokes is an
interesting idea as it should put the jet further into the air stream.
Anyone else have advice on jets, nozzles, float height, O2 sensor reading,
etc.? TIA.
Todd Osborn
San Jose, CA
'68 2L DATSFUN
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