"With the cable fitted, removing the slide is a huge pain. Are there any tips for quick and easy needle adjustment and swaps or is this setup just a massive pita with the cap and spring setup."

"The one downside of this carb is that it is much more painful to adjust the needle settings. Messing with the spring and cap is a huge pain."

"Getting the cable anchor threaded in while holding the spring out of the way is very tedious."


I personally find the PWK fairly easy to work on, about the same as a Mikuni VM.  Once you understand how the thing goes together it goes pretty smooth.

First off, Fast650's suggestion on disconnecting at the twist grip first is a good place to start.

Next, never try to install the cable into the hook and then screw the hook into the slide.  Jeeeez, that's gotta be hard.  How did you ever do it.

Install the needle into the slide and then thread the hoouk into the slide to capture the needle.  Lightly tighten the hook.  It should look like this.

Then push the cable swage into the hook and pull up so that it goes tight in the socket.  Like this.

Ready to rock-n-roll.

Thanks Mike. Those surgical clamps are going to be needed. I used zip ties. What a pain.

I'll post pics of the needle when I get home. Basically, because it's a cheap part, I added a slight increase to the taper. For some reason it wouldn't allow the slide to lower all there way with the short main jets I stalled.
I reinstalled the tall jet and it seated all the way down. I have ordered a few smaller sizes in the taller jets.
I just need to decide what needles to get. I'll buy 2 to try for now.

It's riding really well.

Much more power than stock but I can tell the needle is a little lean. I have ordered a DGK needle that will hopefully be here by Saturday.

I have attached a video of the bogging when I rapidly open the throttle.
Interestingly, I don't feel the issue when I'm riding l, even if I take off fast from a stop.

17aud well spent.

https://youtube.com/shorts/lN7ILSbcCHQ?feature=share

I've stepped up the pilot to 40 and will try the 138 and 140 main jets .
But j think this plug looks either hot or lean? It's hard for me to tell as I'm colour blind.

Hey guys.

So my journey through building this bike and messing with things has been great.
Ive got the new carb (12usd) running really well now. The DGK needle gave me rich bogging at steady high revs at positions 2 and 3. Moving it to position 1 has really minimised it. Hopefully not too lean tho. Running a 140 main and 40 pilot.

I am hoping to make sure I have an appropriate slide cutaway. Hopefully, DBM will chime in with some wisdom on how to identify this.
This is the slide I have. No marking anywhere.

Moarpower wrote on 07/21/23 at 15:57:03:



When I installed my VM38, I had an oxygen sensor and display meter on the bike so I could see what was happening with the fuel/air mixture while I was riding.  It showed me some things that were contrary to what I believed was happening.

THROTTLE ROLL OFF - EXHAUST POPPING.   I had thought that the popping noise out the muffler was caused by the mixture going rich as a result of the air supply being closed off by the slide.  It turns out that just the opposite happens and the mixture goes so lean that the spark plug can no longer ignite the mixture and often the fuel/air mixture goes out the exhaust valve and gets ignited in the hot exhaust system (POP/BANG).  Evidently the high vacuum caused by the closed throttle can pull more air past the partially closed slide than the fuel coming out of the idle circuit can support (The slide needle has closed off the fuel flow from the needle jet)....and the mixture goes very lean.  The TEV (Throttle Enrichment Valve) on the stock carb is supposed to open and provide an extra dose of fuel when this happens......there is no similar circuit on aftermarket carbs.  This scenario is common on any motorcycle with a big piston/cylinder, a carb and a free flowing muffler.......just think how many Harleys you have heard popping and banging as they slow down.  You really should not be richening up your pilot jet or opening your mixture screw to cure this - as you will be running an overly rich mixture while idling or at low speeds.  You can reduce the severity of the noise by adjusting your idle speed a bit higher, or using your right hand to lightly open the throttle to provide more fuel flow (just open the throttle enough to reduce or stop the noise.....not so much that you are actually accelerating).

THROTTLE OPENING - Whenever you open the throttle the fuel/air mixture goes lean.  As the slide opens the vacuum in the carb throat is reduced temporarily....and it takes a short amount of time for the engine to respond and the vacuum to return to the same level that existed prior to you moving the throttle. The slower you open the throttle the lower the vacuum drop will be. This reduced vacuum results in just a bit less fuel being pulled out of the jet needle.  The faster you open the throttle the more you reduce the available vacuum beneath the slide where the jet needle is located.....and the leaner the fuel/air mixture becomes.  The stock carb has throttle butterfly and a vacuum operated slide (CV Carb.....Constant Velocity), and the goal is to keep a proper amount of vacuum and a proper fuel mixture - the carb is doing the work to keep the slide from raising too quickly. (Some carbs have an accelerator pump to provide the extra fuel needed when you open the throttle quickly). With a carb that has a manually operated slide and no accelerator pump - you are the one controlling how quickly the carb opens and the resulting fuel/air mixture.  You should get into the habit of "rolling" on the throttle - rather than just wacking it open and putting the fuel/air mixture into a very lean condition (that can result in the engine bogging until the vacuum and proper fuel/air mixture return).

STEADY CRUISE AND JETTING - When I was jetting the carb and could see the fuel/air mixture on the meter, I jetted so that the mixture was richer than 14.7;1 while the throttle was rolled open, and less than 12.5:1 during steady cruise.  

ADVICE - Don't be overly concerned about a bog if you crack the throttle open from idle.....that is really not a situation that will occur while you are riding, and it is a scenario that really exaggerates the primitive nature of a carb.