DBM, if your reading - When you tuned your PWK38, you mentioned needing needle "N427-48-EEN/017-455".  I'm thinking I might need this needle too.  When I'm on the JetsRUs page for the N427-48, they don't list the EEN/017-455.  They have an EEM/017-454.  Link below.

The needle in my carb is totally unmarked, so I don't even know what my baseline starting point is.  According the the Keihin carb parts page, the standard stock jets are 170, 55 and Needle 48-DDJ for the PWK38 Air Striker.  Since my carb came with the 170 and 55, it might be reasonable to assume the needle is a 48-DDJ.  (You thought the needle that came with your carb might be an ECN.)

I'm struggling to make sense of all the tables and charts on the JetsRUs page.  Codified alpha-numeric soup.  Was your decision for the EEN based on "more taper, but longer and larger diameter" for a leaner more progressive needle and then use the 4th clip groove to adjust it richer.

Where I'm at right now (before testing the 125 main), it feels like the fuel mixture is about right in the low midrange and then goes rich in the upper midrange with the e-clip in the middle groove.  

I'm trying to think through what taper, length, and diameter relative to the 48-DDJ would correct it.

Heck, maybe I just need a better flowing air filter setup and this stock setup with the air box cover removed just isn't cutting it.  But I stubbornly believe I should be able to make it work better.

https://www.jetsrus.com/a_jets_by_carburetor_type/needle_keihin_N427-48.html

First, figuring out exactly what genuine Keihin needle is equivalent to the knock-off needle is a tough job.  Even if you have a micrometer with a vernier, it is still very difficult.  You have to take measurements accurate to within four decimal places and then calculate the angle to within 15 minutes.  It's a crap shoot.  

I can't recall what motivated me to switch to the EEN needle on the 38PWK Air Striker, and I can't find my measurements on the knock-off needle.  I do have a few measurements on other needles that you may find useful.

Remember, only change one thing at a time.  You will get lost if you start changing two or three things at once.  I suggest you concentrate on your main jet.  Once you get it to run clean at WOT, then fiddle around with the slide needle.

I've been down this road with you before.  The main air bleed is important.  It has a huge impact on your main jet.  When I set up the 38 Air Striker, I didn't measure the main air bleed, so we have no way to compare my setup with yours, and you have a stock muffler which is super restrictive.  I wouldn't worry too much about your air filter at this point since the muffler has the whole system stopped up.  You should be able to get it dialed in with the setup you have now (open air box, stock muffler), and it should require a lot less fuel than mine required.

For reference, a Mikuni VM runs pretty good on a savage with main jets in the 190 - 210 range.  The orifice size in the Mikuni 190-210 jets is equivalent to the Keihin 125-132 jets.   But you always must be mindful of the main air bleed.  Generally, the Mikuni's main air bleed is pretty small in comparison to the PWK, but we don't know what size your air bleed is.  We also don't know what size your needle jet is.

You say you have it running decent at idle and part throttle, so I suggest you dial in the main jet and then see how it runs part throttle.  If the low speed ops is good, and WOT is good, then you can dial in the needle.  If there isn't sufficient range of adjustment on your needle, then you will need to select an appropriate needle.  

Here are some needle measurements for you to chew on.  I'm currently running an EGK and it runs very good, but I have a lot more motor than you do.

Thanks Mike.  Yes, you’ve helped me down this path before.  Thanks once again!

I’ll give the 125 main a test run today and report back.  Hopefully it does the trick.  Changing needles does seem like a crap shoot not exactly knowing what I have right now, and I don’t have the gauges to measure it.

I was trying not to rely on jet comparisons to the Mikuni VM36.  The 200 main jet worked well on Woody with the same air box setup and open turnout exhaust.  If the VM36 and PKW38 are comparable at WOT and main air bleed size, the 125 may still be too big on this bike with stock exhaust.  I may end up at a 120.  

The good news is that performance is improving with each change I make.  I’m going the right direction.  And yes, I’m doing 1 change at a time now.  It was only the first rejet that I made 2 changes at the same time when it was very clear I was too rich all around.  Like you said, safer to start too rich.

ThumperPaul wrote on 05/14/24 at 05:30:13:


I think you missed what I was getting at. You can get it to work with the stock filter and the door removed, but performance takes a big hit. It is over a second slower than the stock BS40 with that setup.

Update: The 125 main is very close, but still a tad too rich.  Next up is a 120 main.  I'd try a 122 main but I don't have one handy.

And as an aside, for some reason, the carb decided to flood out the float bowl overflow tube.  Either a bad float needle valve or the float level is set too high.  This hasn't happened until today when I was finally able to get some real WOT pulls in 3rd/4th/5th gear.  Time to do some checking.

Thanks for the history on Sneeze’s experience, Mike.  Today was busy with title transfer this afternoon.  I plan the remove the carb and pull the bowl tomorrow.  I’ve been doing these main jet changes and e-clip changes without removing the carb which has been convenient.

Unrelated, but what size fuel line are you using?  The 5/16th is pretty loose and must be clamped really well at the nipple.  I’m thinking 1/4” would be fine on this gravity fed slide carb (it definitely fits better on the nipple).  I’m thinking 1/4” fuel line should provide more than enough flow for the float needle valve bore to handle (sucking through a straw).  

I’ve read that the stock CV carb when set on run (vacuum mode) instead of prime on the stock petcock valve really kinda needs the 5/16th fuel line to get the right vacuum and flow.  I never experimented with that with a smaller 1/4” line and always used 5/16” line with the stock petcock valve and carb.

I’m using a cheap “Raptor-like” petcock valve with 8mm (call it 5/16th”) nipple.  It can accept the 1/4” or 5/16th” fuel line.  I’ll eventually upgrade the petcock valve, but this is how I roll when I’m seeing if I can get an old barn find Savage running again.

Floats float and structurally look good.