The Keihin PWK28 Carb. Thread

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Dubsey
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#16 Post by Dubsey » Mon Sep 19, 2011 9:30 pm

Was wondering how the reference works from the four letter needle to the three letter needle ?
Have just ordered 4 kits of 10 needles
Will post more details when they arrive
The JJH needles that im using are far too rich, it seems this is the needle of choice for the 350lc boys using this carb
which possibly explains the richness ?
Mediocrity is a sin !

acarver
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#17 Post by acarver » Mon Sep 19, 2011 10:10 pm

Dubsey wrote:The JJH needles that im using are far too rich
Give Sudco a call and get their take on the conversion from the JJH to the NAPE etc.
I don't see it online anywhere (except conjecture from people guessing)
Can you give more information about how the bike is behaving?
Throttle position and rpm where good and bad?
Also, which slide are you running as that will affect the proper needle.(3.5 here)
Andrew

Luther
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#18 Post by Luther » Tue Sep 20, 2011 10:19 pm

Wish I was closer to one of you so I could pass the wrenches, tell how big the smoke cloud was and block the beer cans from hitting the bike while you curse the carb gods.

Put marks on the throttle and housing. Take notes from the start. If you change the clip and ride it go for a long ride with some slow roads and a wfo through the gears if your sure its on the rich side. Write down what was better or worse at any throttle position. If your changing needle tapers you'll end up with a graph of good spots that you can extrapolate an ideal needle from.

Looking at the needle chart and what i've seen with the stock carbs and TM's i'll bet you end up with a J 3deg taper or more with bigger top diameter N or P maybe with a F taper that starts early.

A couple of handy tuning tools are a thumb choke to give some fuel right when you need it to tell if too lean. A roll of duct tape to restrict the airbox or filter to richen everything. You can run without filters to lean everything for a test. Much quicker than pulling carbs.

Good luck and keep us posted.

Masterbill
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#19 Post by Masterbill » Wed Sep 21, 2011 3:19 pm

Hello,
The JJH needles that im using are far too rich, it seems this is the needle of choice for the 350lc boys using this carb
which possibly explains the richness ?
Well I've put the PWK's on my 350 and I ended up using the N68A needle,

This is the standard needle from the KRs the JJH is the standard needle for the KR1s.

I ended up with,

125 mains
N68A needle Middle clip
38 pilot.
Hi flow filter
Modded airbox - snorkel removed and Internal bits.

I tried the JJH but as you've said it is far to rich, my 350 is to my mind pretty good, it pulls well in all gears and it accelerates well in top.

Here's is a from the "other forum"

theahttp://www.yamaha-rd.com/forum/viewtopic.php?f ... &start=30d

don't know if this helps, but it could be worth a look.
RZV 500R .... I had one for 13 years
Thundercat Brakes.
Stan Stevens Stage 3
BDK ignition
Nikon Pipes .

350 F2 Zeeltronic, kenny's pipes, PWK,s

Luther
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#20 Post by Luther » Thu Sep 22, 2011 3:42 pm

I found a page on Carb Parts Warehouse site that shows how to decipher OEM needles. Hope it helps.

Image

Dubsey
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#21 Post by Dubsey » Thu Sep 22, 2011 4:50 pm

Have purchased idle jets and needles from these guys
not genuine but excellent quality
unfortunately I cant use thier mains in my carbs as they are from a KR1s and have a different float bowl

http://www.2strokecarburation.co.uk/

do a search for PWK
Mediocrity is a sin !

Masterbill
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#22 Post by Masterbill » Thu Sep 22, 2011 6:19 pm

RZV 500R .... I had one for 13 years
Thundercat Brakes.
Stan Stevens Stage 3
BDK ignition
Nikon Pipes .

350 F2 Zeeltronic, kenny's pipes, PWK,s

Dubsey
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#23 Post by Dubsey » Thu Sep 22, 2011 8:07 pm

Now running jjk and jjl needles
my bottom cylinders are always the first to foul plugs, so my thinking is they are more rich than the tops
Had a quick run and plug check noticably drier and not as dark, so heading in the right direction
Off to Brands hatch tomorrow so will give it a run and see if the plugs last :grin:
Mediocrity is a sin !

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zomaardan
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#24 Post by zomaardan » Fri Sep 23, 2011 6:16 am

If you going to the track you have more load on the engine and need to be richer then street use.
Maybe i misunderstood and you drive there to watch, i dont know.

Dubsey
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#25 Post by Dubsey » Fri Sep 23, 2011 3:40 pm

[quote="zomaardan"]If you going to the track you have more load on the engine and need to be richer then street use.
Maybe i misunderstood and you drive there to watch, i dont know.[/quote

drive there to watch practice
plugs gone again :-?
Mediocrity is a sin !

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Jeff B
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#26 Post by Jeff B » Fri Sep 23, 2011 6:50 pm

Dubsey wrote:Now running jjk and jjl needles
my bottom cylinders are always the first to foul plugs.
When I was doing a lot of carb testing I had the same thing. After I ran the bike for 10+ miles (with better jetting) the upper plugs looked richer. I suspect that in my case fuel was loading up in the pipes, and due to pipe routing, the lowers fouled easier. In other words, don't just assume the lower cylinders are richer based on fouling.

RC45
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#27 Post by RC45 » Fri Jan 20, 2012 12:41 pm

Null
Last edited by RC45 on Tue Apr 17, 2012 9:14 am, edited 1 time in total.

acarver
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#28 Post by acarver » Fri Jan 20, 2012 2:07 pm

*Edited 4/18/12 - doing more tuning so will have better jetting answers in next few days
Last edited by acarver on Wed Apr 18, 2012 4:24 pm, edited 4 times in total.
Andrew

RC45
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#29 Post by RC45 » Fri Jan 20, 2012 2:40 pm

Null
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acarver
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#30 Post by acarver » Fri Jan 20, 2012 3:10 pm

You're welcome.
One more thing. If you want to run the stock vacuum operated petcock,
the original vacuum source fitting was on the stock carbs.
What I did was take the ext. drain tube off one of the stock carb bowls,
matched a small drill bit to it and drilled one carb's intake boss fitting.
Mixed up some epoxy and pressed and cemented the drain tube into the drilled PWK28 intake boss.
Then ran 1/8 clear line over to the petcock. Works perfect.
Andrew

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