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Post by pdxjim on Jan 3, 2021 22:42:50 GMT 1
Been chasing the jetting on my 4L0 with PWK28's Spec is: Foam filters PWK28 Vforce3 yz85 reeds Skimmed/0-ringed head "Stage 2" porting by Ed Erlenbach Moto Carrera Millenium pipes Timing set at 1.9btdc, BR9ES plugs, NGK LB05FP resistor caps, and standard 40year old ignition (got a Dynatek Banshee coil on order).  Story is: Been chasing the jetting around for a couple months now. Started at 45/JJH #2/145 and found that so lean it would only run on the chokes. On recommendation, got a set of N68A needles and set them at #3. Bumped the mains up to 165 to be safe, and been going up on the pilots til it would pull itsself off the line without the chokes and return to idle without hanging. Now at 52/N68A#3/165 and it still struggles off the line. If I whack open the throttle on the stand, there is a big hollow bog before it catches. On the road it takes some gentle coaxing to get the revs up to where it'll pull away. Still pulls away better on the chokes even when up to temp. Pulls very strong on the mains I've read many (many) PWK jetting threads on here, and don't think I've seen any mention of LC's running bigger than 52 on the pilots. Plugs are dark and wet after a trip around the 'hood, but not done any proper 'chops as I'm still trying to get the pilots sussed.  Gonna try raising the needles a notch as I'm out of new brass to try. |
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Post by Tobyjugs on Jan 3, 2021 23:54:54 GMT 1
I would double check the carb sync on the slide stops (tickover) and on the cable pull.
Then i would keep the pilot air screw at 1.5 turns out with needles fully raised and then the needle fully closed. No long runs especially with the needle dropped. This is too see which way the engine reacts to richer and weaker ranges to give a clue whats happening and which way to go. I find the choke on the PWK's tend to raise the rpm on my bike and it throws me off when trying to jet.
Good luck
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Post by bare on Jan 4, 2021 0:40:54 GMT 1
Using Both Resistor plugs and Resistor Caps is not a good thing. One or the other, Not both.
Unlikely it's your root problem but it's not helping either.
Could fit the OEM airbox? It gives good result on Not 'race only' engines.
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Post by JonW on Jan 4, 2021 0:45:04 GMT 1
Not a comment on jetting, but youve resistor plugs and caps you really should run only one set of resistors as that will be reducing the size of the already small spark from those old electrics.
Also, you are running foam filters, most guys will be running the LC airbox so have a lot less air available when they run those pilots. I assume not with hard back plates? there is a long history of these engines not liking solid ended filters, pure foam is the go if no airbox.
FWIW Each bike needs its own jetting so dont be swayed by what other do on their bike, its just a guide to what you might need.
Tony's suggestion is a good one. I would also clean the carbs and US them if you can. Try and make sure that pilot circuit is completely clean as you could well be running big pilots but the junk in the passageways is making a 52 into a 20 etc.
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Post by JonW on Jan 4, 2021 0:45:44 GMT 1
See bare said the same thing as me while I was typing about the resistors and the airbox.
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Post by bare on Jan 4, 2021 0:48:25 GMT 1
Also :-0 gonna say that 'Our Friend' here has Looong history of Jetting problems.
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Post by pdxjim on Jan 4, 2021 0:51:56 GMT 1
Also :-0 gonna say that 'Our Friend' here has Looong history of Jetting problems. ? ? ? Anyway: - Will check the sync this evening - Will sort the caps when the Dynatek coil arrives this Thursday. - Running long all-foam UNI filters. - Carbs, tank, fuel lines, petc**k, etc all new as of a few months ago. Blockage not likely but certainly a possibility. Def pulls away better with the needles raised a notch to #4 but less clean thru the midrange. |
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Post by Tobyjugs on Jan 4, 2021 7:46:51 GMT 1
Def pulls away better with the needles raised a notch to #4 but less clean thru the midrange. Sounds Like your almost there. If the bike stutters a bit on mid range, that is what i would expect with a tuned bike and foam filters. I believe if the stutter is not apparent and it rides cleanly through the rev range you will be running on the edge of too lean around the 1/4 throttle area |
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Post by pdxjim on Jan 4, 2021 8:10:04 GMT 1
Thx Tony.
I’m gonna give it a rest til the coil and caps arrive later in the week.
Sync was all good despite having the carbs off and on a million times (feels like) the last few weeks. 😎
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Post by midlifecrisisrd on Jan 4, 2021 12:09:21 GMT 1
Also remember on the pwk's the pilot affects the whole rev range so fitting a bigger pilot will affect the mixture elsewhere
Pod filters need big pilots. Only got experience of ypvs but on a bike with airbox it is usually 36-38
With pods on my last build it was 48's
Also with a tune and pods below 3k will be ropey.
Id have thought 52/55 was in the ballpark
As Tony says a little machine gunning on low throttle lower revs is safe
A good few think they have good set ups, even on the dyno but seize it on small throttle openings
Steve
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Post by headcoats on Jan 4, 2021 12:21:06 GMT 1
I had my RED LC YPVS tuned engine with pods PWK 28's and Kenny pipes on the dyno at 152 mains, 45 pilots , N68 on middle clip I think going to a lower needle position (leaner) is risky when rolling off main jet back onto needle My Athena top end had 45 pilots but was going up and up on main jet (162) before I gave up ! Never had that dynoded though but on the YPVS engine bike I put in 160 mains for a dyno run and it lost the top end by about 5bhp 
Bit all over the place lower down but you can see the 152 main jet goes ok Had it like this several years |
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Post by steeley on Jan 5, 2021 7:27:14 GMT 1
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Post by muttsnuts on Jan 8, 2021 20:19:58 GMT 1
what are your air screws set at, they affect the PWK's quiet alot at low RPM
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Post by pdxjim on Jan 9, 2021 7:58:20 GMT 1
what are your air screws set at, they affect the PWK's quiet alot at low RPM 1.75 turns out Dave. The bit that’s driving me mad is the added challenge of having the air and throttle screws on the same side. Makes dialing them in a bit of a hassle, but I'm getting quicker at it.  |
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Post by muttsnuts on Jan 9, 2021 22:30:31 GMT 1
Try the air screws 0.5 (half a turn out), that will make a big difference to the bottom end, you'll find it picks up a load better
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Post by pdxjim on Jan 9, 2021 22:42:00 GMT 1
Try the air screws 0.5 (half a turn out), that will make a big difference to the bottom end, you'll find it picks up a load better Thank you sir.👍 Def idles higher, and picks up and pulls away better at .5 out. Still a bit hollow with some lag when I whack it open from idle tho. Seems like 55 pilots may be needed  While I'm ordering jets, any guidance which direction to go with the mains would be helpful |
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Post by steve h on Jan 10, 2021 0:28:51 GMT 1
No one with a dyno set up near?
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Post by pdxjim on Jan 10, 2021 0:52:28 GMT 1
No one with a dyno set up near? Yeah, a few. Unfortunately none too well versed with tuning 2T twins. Also, still running it in, and wanna be close before booking. I'd love to just hand it over to Mutts, but at 4,752mi it's a bit far. |
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Post by steeley on Jan 10, 2021 8:36:36 GMT 1
Hi i bought a pair of oko carbs some years ago pwk copies . The slide screw being on the same side was annoying me so i re drilled the one carb and fitted the slide screw the other side . I blanked the original with a small screw with a fiber washer .
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Post by stusco on Jan 10, 2021 10:42:52 GMT 1
I bought my genuine ones from allens they did the alteration for me but they drilled squint and it wouldn’t lift the slide ,so i changed it back and fitted idle screws from a kx that you can turn with you fingers no problem
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Post by midlifecrisisrd on Jan 10, 2021 12:26:34 GMT 1
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Post by stusco on Jan 10, 2021 12:48:52 GMT 1
Yep thats the buggers😁
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Post by pdxjim on Sept 17, 2021 17:30:39 GMT 1
Finally grew tired of chasing my tail jetting, and pulled the intake apart. Standard 'valve manifolds with the ears trimmed off appear to have been leaking at the manifold/Vforce3 reed block joint. Dunno why I didn't use gaskets there on my initial build, but they appear to have been sucking air. Reassembled with UPP urethane intakes (without those pesky stuffer ears), proper gaskets and lots of Threebond.  Now waiting on a "Banshee Leakdown Test" kit off eBay so I can make certain it's airtight before starting over on the jetting saga. As before, spec is: EE tuned 350LC barrels and head, Vforce3 reeds, PWK28's, foam UNI pod filters, Moto Carrera pipes, Dyna coil, standard CDI (for now). After hours with the SEARCH on here, seems 50 pilots, N68A @ #3, and 150 mains seems a good enough place to start. One thing the SEARCH has shown, is reported jetting is all over the fcuking map with these carbs. Some running huge pilots (58) and tiny mains (128) and some right the other way 'round. |
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Post by rigga on Sept 17, 2021 19:16:23 GMT 1
PWK carbs do vary depending on what they are fitted to, I think mutts has said, an LC will need bigger pilots, and smaller jets fitted with PWK carbs, than a PV, which is the other way round, bigger mains, smaller pilots .....then you have pods and airbox thrown in .....
Bottom line it make not a jot what someone else uses, its unlikely someone can say fit these, and it'll be right (yes you Bare) so really a dyno set for YOUR bike, is really the only safe way.
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