PWK 28 SAFE pilot jet size

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Headcoats
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PWK 28 SAFE pilot jet size

#1 Post by Headcoats » Fri Sep 08, 2017 5:09 pm

Had my PWKs for years now and they still annoy the hell out of me LOL

I have always kept the same main jet (152) with Ramairs but always had to feck about with the pilots

Tried 40's to 48's then settled on 45's then dropped to 42's but plugs were never burning clean around this size

I had the airscrew 2 turns out on the 42's

Today I fitted 40's and airscrew 1 turn out and it seems to run good and at last the plugs were not wet , but not gone for a spirited ride yet
Dilemma is I run premix and had larger pilots for the shut throttle moments , hoping the rich jetting would keep things oiled
Probably having a senior moment but do these PWKs ever run right !


Or are piots just not as important as the needles and main jets ?
Cryin' In The Beer Of A Drunk Man

evan_calgary
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Joined: Tue Nov 12, 2013 2:34 am

Re: PWK 28 SAFE pilot jet size

#2 Post by evan_calgary » Wed Sep 13, 2017 5:05 pm

No elevation on running issues identified. Provide more info. or this is a total waste.

This sounds the opposite of standard carb tuning unless you run under 1/4 throttle all day. Why are you messing with your pilots so much?

Pilots are not that important...

Headcoats
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Location: Pig On The wall Country

Re: PWK 28 SAFE pilot jet size

#3 Post by Headcoats » Thu Sep 14, 2017 5:25 am

I think with the PWK's there seems to be that each circuit affects the others all through the rev range
If I had blocked pilots on the PWKs , it would make pulling through the midrange a problem
Cryin' In The Beer Of A Drunk Man

JackB
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Joined: Thu Sep 15, 2011 9:06 pm
Location: Chicago Il.

Re: PWK 28 SAFE pilot jet size

#4 Post by JackB » Thu Sep 14, 2017 8:21 am

Its been a couple seasons since I installed my PWKs so I dont remember what jets are in them. Mine runs great all through the season. After I got the jetting figured out All I have done is ride it. I have not touched it since then.
1984 Rz350, Wicked Toomey rep pipes, Dynojet kit,Zeel unit,Toomey Y boot filter.

vmxwinn
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Joined: Sat Jan 28, 2012 3:39 pm
Location: Danville CA

Re: PWK 28 SAFE pilot jet size

#5 Post by vmxwinn » Thu Sep 14, 2017 12:27 pm

Once I jetted mine it has always ran very well through out the rev range. But the one difference from your setup is I went back to the oil injection pump when I installed my PWK's. See my specs below.
85 Y/B, Toomey pipes, PWK 28's, JJH Needle #2, 45 pilot jet, 145 main, Pods, VForce 4 reed blocks, +3 ignition, Milled head 1.1mm squish, R6 Shock, Progressive

Many Vintage MX Bikes, 03 ZRX1200R, 86 Moto Guzzi 1000 Le Mans MK IV, 86 VFR 750, 74 GT 550

Bare
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Location: vancouver

Re: PWK 28 SAFE pilot jet size

#6 Post by Bare » Thu Sep 14, 2017 3:14 pm

Again;; IMO your PWKs are perhaps geriatric removals from a KR?? and as such: likely Worn out and clogged.

PWKs are DEAD easy to jet and typically run perfectly for a looong time.
There is no other real world explanation... Need to either Fix OR Replace them... unfortunately.

Headcoats
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Location: Pig On The wall Country

Re: PWK 28 SAFE pilot jet size

#7 Post by Headcoats » Fri Sep 15, 2017 4:14 pm

I feel I have another issue now
Coming back from a ride the bike stuttered at exactly 5.500 rpm and then refused to rev above that
I stopped and changed the plugs, the left looked ok but the right looked wet
Set off again and just as bad and when I got home, both plugs were wet now

Don't know if I have a carb issue or electrical or mechanical ?

When I put the 40 pilots in to begin with, it was running great apart from a stutter at 5500 but could rev through it no problem
Cryin' In The Beer Of A Drunk Man

GPJeremy
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Location: atlanta, ga.

Re: PWK 28 SAFE pilot jet size

#8 Post by GPJeremy » Thu Sep 21, 2017 1:51 pm

For the layman:
There are three distinct metering circuits on carburetors.
1) Pilot circuit in conjunction with air screws
2) Emulsion tube and needle
3) Main jet
Think of the twist of the throttle as divided into quadrants.
The first 1/4 of throttle pulls air and fuel through the pilot circuit.
The second quarter relies on a combination of needle as well as pilot jet.
The third quarter combines needle and main jet.
It isn't until wide full open throttle that the carb is metering solely on the main jet circuit.
Raising or lowering the needle position alters the transition from pilot to main jet circuits and needle geometry regulates fuel into the emulsion tube at throttle settings before wide open.
At this point just do plug chops to determine which direction to go with your jetting. Be aware that you really should use new spark plugs for the greatest accuracy when doing plug chops. Used plugs don't tell the story that new ones do.




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'85 RZ 350, Toomey pipes, Boyeson reeds, FZ 600 swingarm with FJ 600 Forks and wheels.

Headcoats
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Re: PWK 28 SAFE pilot jet size

#9 Post by Headcoats » Fri Sep 22, 2017 2:44 pm

Sounds like the second quarter of pilot needle transition then I can't quite nail
Cryin' In The Beer Of A Drunk Man

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