Getting to the slide assembly requires a bit of work too.  It’s either pull the fuel tank or pull the carb.  Removing and reinstalling the stock carburetor is arduous if the stock battery box is in the way.

Mikuni VM38 Points of Interest

Lancer’s VM38 kit had almost everything I needed to install and fine tune the VM38.  I had it running great in about three or four hours.

The VM uses an old school round slide with a tapered needle.

The inner workings of the VM are typical of most any carburetor, except it uses a unique float arrangement where the floats remain in the float bowl (on long slider pins) while the needle & seat are in the carb body.  Main jet and pilot jet are standard fare.

Installation and maintenance are a cinch.  There’s lots of room, even with the stock battery box.  Fuel line, vent tubes, and air boot all hook right up, almost like the stocker.  It’s also easy to remove the float bowl without removing the carburetor (especially if you covert to socket-head screws).

Keihin PWK38 Air Striker  

The Keihin PWK38 Air Striker is a variable venturi carburetor.   It uses a semi-flat slide.  The venturi is 37.8mm.  It flowed 186 cfm @ 15” H2O.  It has no accelerator pump.

Installation 2:  Although this carburetor doesn’t come in kit form, it is still very easy to install.  I only spent about three hours to install the carb and fire up the engine.  That included time spent taking photos and tearing down the carb so I could see what makes it tick.

My special air filter setup clamped right up, and I used the Barnett cable that came in Lancer’s VM38 kit.  I had to enlarge the slot in the fitting that accepts the cable barrel.  That was it.  The decompression relay was fine right where I had it zip-tied.  The stock carburetor manifold was a tad loose, but it worked just fine with a narrow stainless-steel worm clamp.  If you prefer a tighter fit, a Mikuni rubber mounting flange (part number HS42/018-42K) works perfect.

If I had not already installed the VM38, I would have had to procure a cable that fits.  I also had to modify the fitting for the cable and come up with a narrow stainless-steel worm clamp.  The PWK was a bit harder to install than the VM.

Tuning 3: The PWK38 was easy to dial in but the jets provided with the carb were way too big.  The needle that comes with the carb has no markings, so it had to be identified through measurement.  It’s an EGN.  I had to find and purchase needles, main jets, and pilot jets.  The grooves in the new needles are narrow and would not accept the e-clip.  This carburetor only costs $75 (from DCMotive), so it’s easier to forgive the narrow selection of jets included with the carb.

No modifications were necessary to get the carb to function properly, but the jet-needle had to be changed from an EGN to an EEN.  Once the needle was replaced, it was easy to tune.  A complete selection of jets, needles, and slides are readily available for the PWK.

Final jetting for this engine setup was: Main Jet #140, Pilot Jet #40, Needle Jet as delivered (fixed .114”), Jet-Needle EEN (clip in 2nd groove), Main Air Bleed as delivered size unknown, Slide Cutaway 7.0, Float Level: level with carb inverted, Idle Mix Screw 1-3/4 turns.

Drivability 4:  It is an excellent carburetor.  It drives almost identical to the VM, hard to tell them apart when you’re in the saddle.

Acceleration 4:  The PWK38 pulled a 4K to 7K time of 2.82 seconds.  It was the fastest.  

Fuel Economy 3:  The PWK38 got 57.2 mpg (2nd best).

Maintenance  4:  All aspects of maintenance on the PWK38 are essentially identical to the Mikuni VM.  Access, adjustment, etc. are almost identical.   Very simple.

Total score for the PWK38 is 20.  

This is the business end of the PWK.  That big venturi is good for about 186 cfm @ 15” H2O.  The fin things are air vanes (the “Air Striker” feature that supposedly amps up the venturi vacuum signal).

The inner workings of the PWK are typical of most any carburetor, float, needle & seat, main jet, pilot jet, etc.