Testing carb setting more today with the pilot and needle, and boy - this pilot really loves to load up on both the stock and this PWK39 carb. I have the idle stop screw in all the way, out two turns. Running the 35 pilot jet. Air screw at 2.5 turns out. The EEH needle sucks and the pilot billows smoke on the trailer in my back yard and will not rev over 5k. Remnicient of the stock carb lingers.

With the stock carb I had found the CGL needle ran very well, and the plug looked nice and black throughout with no white and only slight browning after a day of riding. Stock carb looked great on that needle every time I checked. So I went ahead and put the CGL needle in, and wouldn't you know, things got MUCH better. I'm now able to free-rev 6500 rpm with the needle up one slot from center (So, one point leaner than middle) and idle no longer loads up nor bogs - finally. Keeping at this point on a 170 main jet. Time for some basic pulls in some dirt - first I'll find the upper limit where the Engine won't clear out on a fat main jet, and go down until it clears. then plug chop some new plugs followed by tailoring the needle position and possibly back to the pilot jet for changes; if any.

Does this sound ok? Wouldn't a richer slide like a #6 make worse than my #9?

This PWK39 doesn't have a drain, and so what I've been carefully doing is turning off the petcock and letting the Engine run it mostly out - carefully not to create any run-away. Every time I do this, the Engine starts to pick up idle speed as the carb starts to run out of fuel. I hit the kill switch every time the Engine gets to about 2500 RPM. Theres still a bunch of fuel left in the carb after this. Indication is still rich at idle.

Could the main jet be bleeding in some how?

Coolant bubbling seems to be subsiding for now.

Thank you

Good news on coolant.
If it like a leaner setting than leaner it should get. All it means is that it's a high velocity. If you can dail In the 9, I say run it.
Your providing great info for us pilot guys.
Thanks

I believe I figured out what was wrong with this PWK39 carb. The jet block was tampered with and had a crack in one of the mounts. It appeared to be installed -OK- but I think it probably suffered some leakage. I ordered a new jet block from BDT motorsports (Who was recommended to me by Sudco as the only way to buy just the block), and it arrived today. BDT motorsports buys brand new Keihin genuine carbs from Sudco and takes them apart to sell off individual parts as brand new never used which are not usually available from other places (Like jetsrus or Sudco). Comparison to the old jet block also revealed the old one to be extremely worn out around where the needle goes through. I'd say about 4 clips on the needle would have been needed to compensate for the worn "needle-jet".

I've put it back together. Raised the CGL needle back to middle clip, and will first try the 35/170 jets - and go from there. I'm thinking the 35 may idle lean now but I didn't want to jump out of it just yet. I'll tune the pilot jet hopefully by a responsive air and idle screw now.

Thanks

What a bummer.
Yea might as well start there and see. You'll know real quick if it wants more.
Bummer you go to all that work then urrrrrrrrrr.
When you do get done. would you post me a pic of your over flow location and hose routing

Well, it seems to be idling somewhat the same - that is fat, sluggish, and smokey at full temperature. At least I have piece of mind with the new jet block. I've ordered three more needles: CGQ, DGQ, and EGQ all of which offer a leaner 1/8 to 1/4 throttle in hope to help clear up the idle. At least I have needle options now. Once I get the main dialed in I'll have to watch my plug, EGT, and seat of pants feel for the middle end. I'm actually thinking EGQ may honestly work best to be rich above 1/2 throttle but still have a nice idle and off idle wing. I can always increase the pilot jet and tighten the air screw to compensate for a lean needle down low as well.

I wanted to do something on my pilot tonight, and though I think the RPM may go up with the added carb and intake air-flow - I still thought I should remove Powerbloc clutch weights. So I went from 12 weights per puck down to 10 weights per puck. Its got a black 3-5/8" spring. Maybe with the combo of both larger intake/carb and lighter weights it'll rev past 7200 rpm where it was stuck at after rebuild but with the stock carb. I cant test anything though for several days due to rain and other plans :(

Also my overflow bottle is something homemade that you cant see inside. Its like an oil catch can or something but it fits well and looks good. I didn't want to mess with it other than cleaning, but I cant see inside - so I made a see-through line run along the outside which shows the fluid level then T'ed into the bottle's main over-flow line. I think the problem was however that antifreeze wasn't actually going into the overflow-bottle quick enough, and instead running up my see-through line and then out the pisser under the gas tank. To stop this, I put an in-line restrictor made out of a carburetor jet on this visible line to restrict the flow and get more fluid sent to the actual bottle. It stopped pissing on the ground with that.

Seems I have a jetting, or, setting problem with this PWK39. Jets are 45/178 EEH second richest clip 2.5 turns on the air screw and idle stop turned all the way in. The Engine seems to idle some-what OK, but really likes to idle better on a 35-40 pilot. Unfortunately I have really nasty lean condition after a mid to full throttle CHOP. So, on the main the pilot seems to scream (its FAST, and seems clean but upper limit has not really been met. Didn't have time to try a 180+ main) but when I chop the throttle after a half or full 30-foot sprint the Engine seems to suck down any and all fuel available; to the point of an Engine stall if I let it idle completely down - it stalls out. Restarts fine though. If I throttle up after a 2 second deceleration I can tell the Engine is starving for fuel - and only starts to re-accelerate once I get into the main jet range. I only let the Engine run like this for about a minute or two over the course of several jetting enrichments. As soon as I felt the issue I relaxed and shut her down. Jumping from a 35 to a 45 pilot jet helped but its still way off at deceleration. The plug actually looked brown/black but I know something is up with leaning. I didn't have time to raise the pilot beyond a 45, but I believe the idle would have suffered badly with something like a 50. Raising the needle helped - in fact every jetting enrichment helped gain mid-power - but this lean deceleration problem is a real problem at the moment.

This happens sometimes on jetskis, and it is usually because of pop-off pressure being too high. I think in a dirt carb the needle and slide are points to observe.

I'm thinking the #9 slide, which is a very 'lean' slide may be causing this. Maybe I should drop to a 5 or 6 slide?

More on the main jet tuning. What I usually like to do for the main is - either start big, or increase jetting until the pilot won't clear out. What I usually do is give a short, 1 second full throttle to quickly test if the main is too fat or not, and if its not to fat then I go larger. I did not meet the limit yet with a 178 main meaning I'll probably put a 185 in next. 185 is the largest main I have on hand.

The stock carb didn't do this at all.

What is your new max RPM since you took out weight?

I didn’t look actually, and didn’t really let it wind up for more than a sec or two. The low rpm lean scared me off from doing even a short pull.

On the phone with Sudco again today, and after all - it looks like I was just reading the PWK39 slide wrong. Apparently a 6 and 9 look similar and the K-mark on my slide was barely showing and so I was mistaking this #6 for a #9. So, it WAS a #6 after all.

Given the lean low, I've replaced the 45 pilot with a 48, and also put my DEE needle in there. My DEE needle should be the richest needle I've got in my collection for 1/8-1/4 throttle (Diameter is E). Set it on the middle clip. I will need to test at a place maybe next weekend. Given the result I may need to get an EEF +/ needle, or maybe even a #4 or #5 slide if the idle circuit craps out from the richer pilot jet. Sudco said normally the #6 should work for FL400r so I'll give the #6 another go. If the Engine likes the larger pilot jets and DEE at 1/8 throttle but won't idle right I may need to drop the slide size to 4 or 5.

With the DEE, I'll need to keep watch on 1/2-FULL throttle as it may actually be leaner than my EEH needle... I may need to buy one in between - maybe EEF? Will see.

Starting to not really like this PWK39 carb. Earlier today I could not get the Engine to idle with the 48 pilot, and so that's when I realized my FL400r choke button wasn't really making much difference. Push it in - and the idle barely changed at all. Pull it out and barely a change. Stalling out idle with the idle stop all the way in and a 48 pilot.

With this carb, I received a stock choke lever. So I pulled the Pilot choke asm out and measured compared to the stock PWK39 choke - and the pilot choke doesn't quite reach as far in as the 39's original choke. I'd say the Pilot choke is about 1~2mm shorter than the original choke lever.

So I installed the original choke and started the Engine. Immediately noticed a stronger cleaner idle. Still seemed quite rich but definitely a 2~300 rpm difference, and its not stalling. Immediately felt a little better and so I looked around at the stock choke's adjustment - but there is none except the tension adjustment down at the button. HMM I thought - Maybe I can take a razor blade and 'shave' off a 1mm layer of the rubber cap? That might work. HMM..

Then I looked at the carb side of the choke where the plunger and spring was. I carefully took the plunger off the cable, and then removed the spring. The plastic part that screws into the carb then slid off. I looked inside, and noticed that theres about 1/4" worth of material which can be carefully hand-drilled out which would make the plunger stick out a little further to cap the carb's choke circuit. I used a 15/64" drill bit BY HAND (NOT in a DRILL) and started to shave out about 1~2mm worth of the backing on the choke's CABLE side of the screw-in plastic.

Like, in this picture; I shaved with a 15/64" drill bit from the left down inside this piece.

After assembly, I was able to verify that when seated the choke cable had a bit of extra slack - so its seating better now.

Dang, I was going to ask about the choke a few pages back, but im unfamiliar with the pilot choke.

My CR had the idle adjustment on the pull knob for the choke. My buddy cranked it way out one day as a joke! Took a while to figure out WTF was wrong.

I guess the pilot has the lever type?

CR250r has a PJ carb right? The idle/choke adjust on those were terrible.

that plastic problem where the choke cable fits, I solved it like this ...

@galimberti, Where did you get that brass version? Link?

Send it to a cnc, copying the plastic

OK well, I think mine is going to work as modified.

Not a lot happening over here. The weather has been relentlessly hot, wet, humid and its rained hard every day for 2 weeks. Plus wife broke her hand. I don't know when Im going to get back to tuning and testing at this point - maybe two weeks.

I did just score a pwk39 #5 slide which I'll add to my pile of carb parts. If the #6 still comes up lean off-throttle with the DEE needle I'll be ready to pop the #5 in and go from there.

In another thread I posted about PWK39 #5, #6, and #7 slides here: viewtopic.php?f=1&t=18049

That thread was quiet so decided to post-up findings here. The solution for me was to modify my #6 slide into a #7 slide. With just changing to a #7 slide, the Engine GAINED ABOUT 2000 (Two-Thousand) rpms at IDLE! With that, I was able to un-screw the idle stop screw about 8-full turns to get the idle back down and comfortable at 1500rpm - and so my idle-stop screw is no longer screwed all the way in. I also changed my base jetting to 48/185, 2&1/4 turns on the air screw, and J35A needle (Stock PE34 pilot needle).

To the best of my knowledge and ability - I've measured the J35A and have determined that it would be much like an FFL needle (Which you CANNOT buy), but also shorter than the standard needle-66mm. At 3/4 to full throttle it should let almost all of the main jet in which should be a safe start. D-1 is L at 2.705mm which is giving a very nice clean off idle condition, and the whole setup no longer FARTS off the line. I'll see how it feels mid-to-top once I get this setup rolling. For now I'm waiting on a new 2.5"x3" 90 silicon intake hose to arrive.

Then up next will be dialing-in the main jet to clear out and get a decent plug chop going.

I could not for the life of me figure out why the stock Pilot choke was not fully seating this PWK39 properly - even after modifying it - still wasn't working right. I've decided to just use the PWK39 choke for now but the down-side is I won't be able to activate it while driving. Its noticeable how the PE34 choke doesn't work - Engine stalls at idle = poo. while the PWK39 choke works fine. Currently the Engine starts extremely easy - even without the choke. Also I think since the slide/idle stop is much lower than when having the idle stop screw propping the throttle open - it makes for higher vacuum across the idle fuel circuits as everything is responding very well now. I believe that in a perfect world a choke should actually not be required.

I don't have a choke OR a primer on my jetski - and once the pumps pump she always cold starts in 5~10 seconds and instantly when warm.

The #7 slide, as well as the stock PWK39 choke - FIXED this carb

In starting to tune my pilot, I dialed jetting in on the PWK39 at 48 pilot, 2.25 air screw, ECL needle, middle clip, #7 slide, and main jet between 182~188 on C12/VP110 mix race fuel. I've still got to hone in on a final main jet - but can tell you that with a 190 main, she wasn't able to fully clear out.

I believe I have another issue which I could use some help on. Seems the Engine is stuck from revving past exactly 7200 RPM as measured by my digital tiny tach - and I'm not really certain why? Its like a rev limiter at 7200 - but if you look at page 2or3 I disabled the rev limiter on the CDI (Capacitor Discharge Ignition). So, Im not sure what is going on??? Its not the PWK39, as the same exact 7200rpm limit was also experienced with the stock carb. I also removed a total of 6x washers from the PowerBlok clutch - and yet still 7200 rpm. What, electrically speaking; would be causing my rev to limit at precisely 7200rpm with everything that I've done?

-Ported cylinder 1.5mm over
-Race head with 47cc dome
-175psi compression
-Modified CDI (Capacitor Discharge Ignition) (No rev Limit)
-Aftermarket chamber and silencer

In other problems today and the main reason why I could not finalize my main jet - was I bent the left-side tie rod - which canceled my day.

Plug pictures after the day. I may try my FFL or EEK needle next trip.

Also something 'new' I may have found wrong. I started through the service manual on ignition related things and have found the spark plug cap may be out of spec. The cap (Pictured) by itself is measuring 5M~20M Ohms when it should only be about 4K~6K Ohms. SO, I may have found an ignition problem?

Everything else in this list looks -OK-.
Ignition coil is measuring .1Ohms across Primary, and 4.5K across secondary.
Pulse generator is measuring 360Ohms (90F degrees)

Bad spark plug cap? I cut it open and the guts are failing resistance tests.

Interesting and good find on that sparkplug cap.
I remember some guy named Hoser who used to tell everyone to cut back the high tension lead about 1/4" and screw the cap back on. Never thought about checking the resistance on any of mine.
Just curious but how did you measure it ?? The wire goes all the way back to the coil so how did you determine the cap and not the wire was the issue ?? I am NO electrician. I hate electrical. All I know is if you give it the lick test you end up on your azz. Can you remove the wire from the coil ?? Help me out here and explain how to do it.

Edit: I also started a post a long time ago and asked if a guy could use an automotive style coil like an MSD or Excel super coil, but no one answered my question.

When I measured the coil from either spade terminal to where the spark plug goes, I found about 15Million ohms, when the book says it should be 8K~10K. I un-screwed the spark plug cap and then I measured again from the coil spade terminal to the wire end - and I get 4.5K ohms, which is normal meaning my coil is OK. By process of elimination I decided to measure the cap by itself and well; it seems to be the problem.

I think I can get an NGK brand 5k resistor cap from a local shop. I'll check first thing tomorrow.

Upon assembly I'll cut the old wire back about 1/2" so it'll all be new. While I am sure the spark plug cap is defective; I'm not sure if this will solve my precise 7200RPM rev limit issue. Honestly the machine operates smooth and with authority I'm a little taken back by this defective spark plug cap at the moment.

If this does solve my issue - I may have to consider re-tune/re-jetting. FUN!

Do you think a guy would be able to run a super coil ??

Its probably not probable or beneficial unless you go with a full aftermarket ignition - it probably won't even fire otherwise, plus I'd hate to risk my FL400 CDI (Capacitor Discharge Ignition).

MSD does make a coil called a Single Tower; but again these are normally run off an MSD Pro Digital ignition system. The difference is with that kind of system - it runs off the vehicle's lighting system and 12v battery; where-as our CDI (Capacitor Discharge Ignition) based system is run off the pulse generator. Those are two very different systems with different starting/ending voltage requirements. Some of the Pro Digital stuff can multi-fire at low rpm for added torque also.

Besides - I don't think the Pilot coil is all that bad? I've seen similar coil setups in very small 2-stroke engines which run 10k+ rpm so there is probably no need to change. Now - if we had some aftermarket ignition options with programmable timing curves then that's a different story but can also be highly costly. A new spark plug cap is $5 while a new Honda coil is about $50.

Thanks for the info.
That's what I wanted to know -- dumb idea.
I am no electrician but the explanation does make sense.
The reason I even mention it is because I thought my oddy spark looks weak but my machines all run well. Yours on the other hand falls on it's face at 7500 rpm so that just screamed ignition to me. Also I found a pdf online where they experimented with auto coils. The RD350 is a two stroke just like our machines but it has a points system. I'll post the pdf here just for fun.