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PWK33 450 Project

Ordered the clutch plates today, will keep running Rotella.

Hot day runability is good. 94F/40%RH and no misses, sneezes, snorts or other bad manners. Idle on the off-ramp stayed steady right up to the need for more rpm’s, then a slight hesitation that I attribute to large carby/small engine syndrome.

I will readjust idle speed from 1200 to 1400 and see if that helps. The problem with that is the advancer is at risk of non return at around 1600 and rpms will hang up at 3000.
 
There I was, zipping down the highway...
...when all of a sudden
It's only running on 1 cylinder.
The other one up and ran the other way!
More importantly, decided to not run at all.
Drat of drats! Woe of woes!


I'm freaking out as I'm at speed and don't really relish the thought of waiting on the side of the road, so I carry on to my destination (work) stop at the guard shack for temperature screening (where the bike dies) then onto the parking lot where I have lots of room, access to tools and so on.

Turns out somewhere along the way (I'm assuming a backfire event happened), something happened that popped the right side carburetor off of the spigot. "So", says I, "this is an easy fix". Loosen up the clamp, slide things together, tighten the clamp - then watch the everything slide back apart as if greased.

Turns out this is a self-inflicted fail as I was experimenting with intake/spigot lengths v. side cover fitment and shortened the spigot, which removed the previous groove and left a smooth spigot to grab onto.

The lessons learned is all carbys need the groove, or grooves, to properly capture the rubber collar under all pressure, temperature and structural conditions. I've removed both of the spigots and machined in grabby grooves (catchy don't you think?) on the outer diameter of the spigots. Reassemble.

The ride in was uneventful, lesson learned.

BTW, no help in readjusting idle speed. For this bike, '68 CL450, 1200 is the max. I'm also at 1 turn out on the air screw so will play with 1 1/4 turns to slightly lean out at idle, play with that for a bit.
 
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This week's mileage was 42.3mgp
Riding was a mix of 70+mph interstate blasts and in-town / back road jaunts of 45mph.
Idle time is at least 2 minutes before starting out.
Enrichener time is almost nil as the bike will stay running without them, after its initial start.
Overnight temps 68-72 deg F and daytime temps 93-101 deg F. Average RH is 50%

Temps are creeping downwards now so will see how that affects mileage.

My wish list next step is to start again with a fresh set carbs/new setup on another bike for repeatability. Just don't have the budget....maybe for Christmas!
 
It should be stated too, I have been using premium fuel 93 octane pump gas. Further, it's likely a mix of a cleaning the "hose full" of regular and the rest is 93. Typical capacity at refuel in my CL is 2.1-2.4 gals. So whatever that mix results in octane.

Opening up the air mixture screw made a difference, there is now no "loading up" at idle, idle speed is ~1200. I still baby at off idle starting in gear, i.e. it likes a 1500-1600 idle speed so have to sort out the advancer springs to be a bit stronger so the speed doesn't hang up - they're from MikesXS, from a XS650 advancer - the only viable replacements I could find several years ago.

The moral of the story is the PWK33 is an exceptional replacement option to the OEM carburetion setup for runability and superior in performance. They are not sensitive to air filter size/shape as a bonus.

Further, I like them better than the Mikuni VM32's as they transition from circuit to circuit in a smoother, more seamless manner. Perhaps if I had spent as much time sorting jetting with the VM's as the PWK's I wouldn't feel this way but I used the jetting from the typical kit offered and so believe it a apples-apples comparison and will stand by my evaluation.

I wish I had access to a flow bench to get loss/deltaP numbers on all of these units and do a proper comparison. I'm also intrigued by the new design Amal Concentric MkII's as they're supposed to be a smooth-bore design but their cost is way too high.

Of course, this just my opinion, but Jay knows better, am humble too.

Until the next adventure, carry on!
 
I may have missed it, but what was the final decision for the air filters? My next question is not twin-related, but do you think the PWK carbs would be reasonable candidates for a single, like an XL350?
 
So far, the air filters haven't been a deciding factor in jetting so intuitively I may have some work left. but in the thread, I was satisfied with the conic ones shown. It's possible they're more a screen than filter though with no restriction. I guess I have to check that too.

Yes, any carb can be a candidate for any bike. That said, some are better than others.

As a metering device, the PWK's are outstanding, better than the VM equivalent, IMO. If you use a same or one size up equivalent to OEM, use the same jet sizes, including needle. The needle will require some measuring and comparing as the numbers won't align but its easily done. use the same number pilot jet as they're all based on a size standard in 1/10 mm. the mains are more problematic as the hex Mikuni jets are a flow std while the Keihin are a size std, in 1/10 mm. Where I'd start is if the OEM carb is a Keihin, then just carry over pilot/low speed, mains and needle. that's your start point and jet from there. It should be pretty close.
 
...these old bikes *sigh*

This past winter, I've been riding a 1970 CL450 that is completely stock except for a red blinker lens cover and my oil pump, oh, and LED bulbs. It has 14H carbs and paper air filters, points ignition. It uses oil with 13K miles on it and isn't performing very well at interstate speeds. When called to go from say, 65 mph to 75 to pass or get out of the way or something like that, it's sluggish. I've noticed that with other fully stock ones too. At the end of a short ride, my hands are numb.

Over the weekend I switched over to my test bike, a 68 CL450 with 30K miles on it. Doesn't use oil, has electronic ignition and PWK33's. What a joy to ride! doing the same speed-up maneuver, I can feel it work hard to accelerate and it gets to the desired speed quickly, no hesitation. This bike has a flakey mechanical advance so idle sometimes hangs but eventually reduces. Stock exhaust.

Today was low 40's F when I started out and the bike fired right off and stayed running. The moral of the story is this combination of ignition and carbs, both fresh, really turn this bike on. Seems to run smoother too, no numb hands. Well, not from vibration that is, because its still cold!

Anyway, huge grin today for a fun ride into work.
 
+1 on UNI filters

+1 on uni filters, they fit well, have good air flow and most importantly do not block or distort the air flow to the inlet holes for the carb piston. No jetting was required on my bike which had been running rich due to the use of the very dirty original filter. These filters come with the parts required to use them with original covers.

https://www.amazon.com/uni-LEPAZA65694-Uni-Filter-NU-4001/dp/B000HSARVW
 
dgallagher said:
+1 on uni filters, they fit well, have good air flow and most importantly do not block or distort the air flow to the inlet holes for the carb piston. No jetting was required on my bike which had been running rich due to the use of the very dirty original filter. These filters come with the parts required to use them with original covers.

https://www.amazon.com/uni-LEPAZA65694-Uni-Filter-NU-4001/dp/B000HSARVW
Click to expand...


They're great on 350's and fit under stock covers. I've heard cheap pods are improved by an extension of 1 1/2 inch, same reason.
 
Update.

I had an episode where the bike fired, then quit and wouldn’t run. My initial thought was the E ignition but that’s proven as robust as they come, awesome stuff! What happened? Fouled spark plugs.

To my thinking, that shouldn’t happen so am addressing that issue with a new needle jet, DGN. That change now forces me into a new round of tuning as there is a giant hole at 1/4-1/2 throttle.

Fuel economy is a useful 57mpg, mix of city and country roads, avg 45 mph. Wife forbade expressed worry at interstate speeds (80ish in my area) and risk thereof, changed my route. Anyway, once mixture is fixed, economy should improve. 16/35 sprockets.

yesterdays adventure was rebuilding the starter, yuck, what a mess! Working again. Still, it was a 1-kick bike in the morning, very easy.

Another improvement will be cable operated enricheners as reaching down to on/off the knobs is quite inconvenient.

Finally, I think I’ve found a bolt in replacement for the OEM keihins allowing use of the stock air filter system and seamless fit under the side covers. Fingers crossed, they’re coming from overseas and should arrive mid Jul.
 
Jays100 said:
Update.

I had an episode where the bike fired, then quit and wouldn’t run. My initial thought was the E ignition but that’s proven as robust as they come, awesome stuff! What happened? Fouled spark plugs.

To my thinking, that shouldn’t happen so am addressing that issue with a new needle jet, DGN. That change now forces me into a new round of tuning as there is a giant hole at 1/4-1/2 throttle.

Fuel economy is a useful 57mpg, mix of city and country roads, avg 45 mph. Wife forbade expressed worry at interstate speeds (80ish in my area) and risk thereof, changed my route. Anyway, once mixture is fixed, economy should improve. 16/35 sprockets.

yesterdays adventure was rebuilding the starter, yuck, what a mess! Working again. Still, it was a 1-kick bike in the morning, very easy.

Another improvement will be cable operated enricheners as reaching down to on/off the knobs is quite inconvenient.

Finally, I think I’ve found a bolt in replacement for the OEM keihins allowing use of the stock air filter system and seamless fit under the side covers. Fingers crossed, they’re coming from overseas and should arrive mid Jul.
Click to expand...

Looking forward to seeing it. I'll stick with the separate-and-annoying enricheners on my Mikunis, too much of a PITA to bother with on a "finished" bike.
 
Changes in jetting to the PWK’s yet again. Changed down on the pilot, 35, and up on the main, now 130. Needle is a DGN (5th clip) but that’s going to change to a DDN…I think…. It runs so sweetly!

Heres a new one for ya, 32mm and fit under the side covers. Not so nice running as yet.
F928E200-9AEA-47A3-94C6-989F080AA6CB.jpg
Cant say I’m happy with jetting but early days. More tinkering is in my future!
 
Many factors. On a cold morning and I don’t need the enrichener, generally too rich. Sitting at a stop light, loads up, too rich. Plugs black and wet? Still, when it pulls up a long hill, it doesn’t misfire and will accelerate. When I roll the throttle and bogs, middle is too lean. So yes, runability is my method.

I also use kyajet, a jetting app. It just graphically shows more/less fuel based on PWK jets and it’s overall effect of change from a baseline.
 
You sharp eyed folks will see my drain valve hose connected into the crossover. During the jetting process, the tank has to be removed many times so I saved myself from frequent gasoline messes by putting in a tee and drain. I’ll remove once I’m happy with the combination.
 
I'm always interested in tips related to jetting -- thanks for sharing your experiences. I had never heard of kyajet, so I'll have to look into that.
 
(Jays100:) You sharp eyed folks will see my drain valve hose connected into the crossover. During the jetting process, the tank has to be removed many times so I saved myself from frequent gasoline messes by putting in a tee and drain. I’ll remove once I’m happy with the combination.
Click to expand...

Clever! Thanks for pointing that out - my eyes ain't what they used to be, but I see it now! Draining tanks is one of my least favorite tasks on these bikes.
 
PWK33 Jetting has evolved somewhat with another problem revealed.

There now exists a condition where the bike just "runs out of gas" when nearing reserve capacity/miles. When the fuel petcock is set to "reserve" the bike takes a long time to recover. Mostly I've attributed to large carby's float bowl capacity and left it alone. The problem has worsened. With the theory of runs out of gas is reality, I've inspected/opened up the gas cap vent, no help. Then last night, inspected the sediment bowl filter. The bowl was clear but the filter was indeed clogged. Cleaned and reinstalled, the "runs out of gas" phenomenon has not recurred and problem likely solved.

Second issue is a WOT (Wide Open Throttle, akin to WFO for you racers) bog at anything over 3/4 open. Chasing jetting all over creation has not netted any changes so something else is at issue. Remember earlier posts on problems with the air filter? When removed and ridden, jetting went from borderline rich to borderline lean and the WOT problem seems to have disappeared. New air filters of much higher volume have been ordered as touched on then. Shoulda listened to you guys!

The saga continues.
 
Glad some of it is sorted. I know you will keep us posted on things as they evolve. The next question is, how is that ignition system coming along?
 
Ignition is WIP (work in progress) the last issue is a hall switch is dithering. kinda sorta important but an alternate was already in work several months ago.
I've designed a different mount (based on G's input) but haven't gotten an update.

Once the hardware and mounting are finalized, writing the software is next. Software is G's forte' but there will likely be an iteration of hdwe/sftw integration after that. Then, road test. Looking at late next year for availability - no promises. Part of my problem in road test is to drive under the best conditions, okay. But, add to "coffin corner" conditions of high temp and voltage, voltage spike, means I have to deliberately simulate damage to other components. not looking fwd to that, but must be done. Am thinking I can make an oven fixture and a auxiliary power supply. Wife won't be happy with that.....
 
Todays ride in was in the low 50's F, typical New England fog and heavy air, enrichener was needed for initial fire and about 10 secs of running before it would blubber. Once released, the idle was low but steady. Oil circulation is audible, that is, once oil is circulating the noisy engine quiets right down.

I've been chasing a serious bog on the main jet circuit/WFO and have been going up, up, up, and was at a 150 with things only getting worse. Then, the too small air filter came apart and a new one was sourced. A pair was found on eBay that fit a scooter application, turns out they fit the PWK/450 perfectly. They don't quite fit under the side covers.

450 Air Filter.jpg

The high speed bog was distinctly on the main circuit so last night, I went the other way in main jets....all the way down to a 120. This morning, going up a long hill in 3rd, resulted in a clean rev through redline. I still have work to do, the needle is on the 5th clip position (needle raised as high as it can go) that will get replaced with one to run in the middle position. I just need to ensure all other runability is unchanged or better.

Here's where I am on jetting:
PJ 38
MJ 120
Needle DGN/5 (to be changed)

All else is the same. i.e. cutaway: 6, float level: 19, idle mix: 1 turn. Electronic ignition with E3 sparkies. Regarding sparkies, I'm really liking the Autolites they have been working perfectly in another bike and have procured many more.
 
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One more thing, the petcock screen was almost fully clogged. Cleaning that made a difference in fuel flow. Go figure.

Mileage at last fill up with the 150 MJ was 55 mpg, in-town/rural riding with 45 mph typical speed.
 
76Twin said:
Better in terms that is it more precise yes but the work involved seems better suited for fuel injection application where precision is required.
The oem carburetors aren't all that precise and I don't know what increments you can get the jets for these PWK carbs.
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@76 Twin, sorry I missed this but all parts are adjustable on the PWK with the exception of the emulsion tube. Still, the Needle options available are vast and there has been no need to change that. I wish this style was available in 31mm throat size, it's a better all around performance match in my opine. The 33's are on the edge of too big on a stock motor even though that's also the port size.
 
What I meant to say was that the pin thingy extends into the carburetor gas orifice thus reducing the area considerably. By doing that, reduces the fuel draw at startup. There would be no (or very slight) reduction of the air flow through that circuit but significant reduction in fuel for an overall leaner mix.
 

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Faced with the same situation with the Mikunis on my red 450, I do cold starts this way (though not at mid 40s temps, I'm not riding then): turn fuel on, turn enricheners on (mine are the lever style), kick the engine over 2 to 3 times with ignition off (depending on how long the bike sat between starts, and ambient temp), then turn enricheners off, then ignition on and kickstart. Typically it settles down into its good cold 1200 rpm idle which is fortunate for cams and followers, then I wait for the 2 minute oil flow period. A cable would be nice, but these enricheners seem to be mostly on/off functionality.

Jays100 said:
Note the proboscis or pintle or armature that would inserts into and occludes the orifice to effectively reduce the flow area by 50%.
Click to expand...

Jeez, I'd have to use the dictionary to fully understand that sentence.
 
When I click on the "edit post" button, all that happens is a blank window. I was expecting the text in the window, but it's blank.
 
...and by editing, i lost it all.
taking my marbles and going home, I tell ya!

can you get the original text posting back?
 
Jays100 said:
...and by editing, i lost it all.
taking my marbles and going home, I tell ya!

can you get the original text posting back?
Click to expand...

Well first, what I was doing was making a joke about the 50 cent words you used in that sentence. Didn't look like it needed editing to me though.

All you can do to try to recover the text is open a new post window and see if the "Restore Auto-Saved Content" button is there at the lower left, but since you did already post it once it might not help. If I open an Edit of a post and it's blank, I click Cancel and then copy the entire text of the post as previously published, then go back and try it again with a backup in hand, so to speak.
 
Computer probs, lost the post so will try to re-create.

At cold startup this morning, the bike would only take the enrichener for a brief second before blubbering. I need to lean out the start/enrichener circuit.
see above post.
 
Jays100 said:
Computer probs, lost the post so will try to re-create.

At cold startup this morning, the bike would only take the enrichener for a brief second before blubbering. I need to lean out the start/enrichener circuit.
see above post.
Click to expand...

I guess in northern climates like yours more choke would be needed so you'd have to address it. I wouldn't want it blubbering at higher rpm than we know is safe for our cams and followers either, but at least your oil pump will cut down on the required low rpm time. I'm lucky my area is rarely that cold when I'm planning to ride, even the years when Chris is down during the late winter or early spring.
 
Turns out I already have a set of cable operated plungers, with pins. Will install this weekend.

And the pump does make a difference!
 
Here’s a 1000 mi report on the PWK’s.
I like them.



Seriously, as in all things, there are advantages and disadvantages. To start, I was able to get it to carburete cleanly such that not only did it feel crisper, fuel economy was consistently over 50 mpg (52-54). For comparison, the stock 14h under the same conditions is consistently 47 mpg. At interstate speeds, the bike never stopped pulling. 14h kinda just runs out of steam at about 80…

The transition to reserve, refill of the float bowl, is very quick on 14h, but quite long with the PWK’s. At interstate speeds, the clench factor is high.

Im seeing some wear on the slide Chrome coating. Keeping an eye on that.

The bell mouth / inlet is large so they done fit under the side covers. If you like that look, is good, if not, well not.

Parts and jets are readily available, they look cool and the effort was fruitful. I hope you all got something out of it.
 
Here's my installation:
PWK33 RS.jpg

I made the manifold tubes in my garage and the air filters are from eBay for a scooter application. Overall the cost was quite manageable.
 
One thing I loathe, despise, hate and detest (neither do I like it...) is that doggone crossover tube underneath the tank. I've adjusted both sides hose connector tubes on numerous occasions to clear my various carby experiments as it's always in the way.

I'm "this close" to changing over the whole thing to a setup much like the early Triumph Bonneville's (et.al.) did with the Right side valved as Reserve and the left side valved as primary. Then feed the two carbs via splitter underneath the carbs. It'll be a little busier between the carbs but the space is there. Plus, the fuel flow path is a bit more efficient. Will likely have to add filters but that's an easy fix.

Having vented my ire, I likely won't do any mods given it's a very clean '68 and don't wish to get too far away from original.
 
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Jays100 said:
I'm "this close" to changing over the whole thing to a setup much like the early Triumph Bonneville's (et.al.) did with the Right side valved as Reserve and the left side valved as primary. Then feed the two carbs via splitter underneath the carbs.
Click to expand...

That's actually not a bad idea. As you know, I'm feeding 2 Mikunis through a Y fitting from a single outlet on my red 450 and it works fine.
 
The CL pipes don't contribute to high speeds either, the bend is too tight, power loss at high rpm and thus exhaust gas speeds, too much resistance. And may I ask why you using 2-stroke carbs on a 4-stroke bike ? The cut-off angle of the slides are different, resulting in (possible) nasty behavior between 2K to 5 K rpm's.
 
I get those questions a lot. My purpose was to have an alternative to the Mikuni VM’s out there…also 2 stroke original application that were adapted to 4 strokes. Interestingly, Mikuni bought designs from Amal and improved on them. The Amals were 4 stroke applications, same for DelOrto.

In engine gas flow, the minimum bend radius best practice is 2 pipe diameters so if the ID of the pipe is 30mm (for instance, I don’t recall exactly what it is) then 2*30=60. I.e Minimum bend radius is 60mm and I think they are right at that 2D number, whatever it is actually, but my point is that Honda was consistent with that best practice. It’s interesting that flow loss is exactly related acoustically. So for a tight bend rad, the noise goes up with increased resistance. The CL pipes are relatively quiet. In any case, ancientdad is using low pipes.

As to carbys, they none of them care what engine they’re mounted to, they’re all jetting adjustable. For the PWK33’s, there is a plethora of needles available and I simply went up on the needle D diameter until the cutaway was right for the mixture @ slide position. They work well with no stumbles or hesitations throughout the rev range. I haven’t found any difference in runability with back to back tests CL or CB.

The new KSR carbys don’t have the same variety of needles so the cutaway option was used to clean up the low speed runability. If that didn’t work (which it did) I was going to reset the float level 1mm lower and go that route.

Hope that explains.
 
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