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.
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.
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.
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.
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
Last Edit: Jan 4, 2021 12:33:46 GMT 1 by headcoats
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 .
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