The Keihin PWK28 Carb. Thread

[ChequeredFlagRacing]

I tried to setup the bike with the stock airbox.
Olli

Hi Olli

do the carbs fit in the elephant ears?

[Motolli]

Hey ,

They do not fit without some handmade adaption. Search for my “ winter stripdown “ thread. There are some pictures. Don’t know how to link it in here, sorry.i am still working on the jetting. Found out, that my configuration runs very smooth from very low RPM s with the JJH needle on clip 4 Which is very rich. Pilot jet is today 46, with air screw 1 out. Also richer than before. Had to restart from scratch, as removing the head gasket ( slightly higher compression) seems to need more fuel.
To be continued.
Anyway these carbs are a win for this bike !

[Vin]

I tried to setup the bike with the stock airbox.
Olli

Hi Olli

do the carbs fit in the elephant ears?

You can fit KR1/S inlet rubbers to the ears with some modification to the rubbers, unfortunately I didn't get to trial fit to standard fairing as my project changed to fitting a yzr fairing. And unfortunately I am unable to load any pictures but they can be viewed on my site.

[ChequeredFlagRacing]

You can fit KR1/S inlet rubbers to the ears with some modification to the rubbers, unfortunately I didn't get to trial fit to standard fairing as my project changed to fitting a yzr fairing. And unfortunately I am unable to load any pictures but they can be viewed on my site.

Nice one

[ChequeredFlagRacing]

[Motolli]

Hey Vin

This looks really smart ! For now it’ s driving season, any improvements like this are postponed to the next winter for me. Enjoy the summer for everyone, let it smoke

[Luther]

I collected 4 YZ85 PWK 28's and all looks good but I have 3 different needle jet shroud heights. I'll measure and see what I have but what do you guys have?

[hybrid]

I'm about to finally spend some time on jetting which is long overdue.
For those of you who have switched to PWK28 - does your bike idle up when you open the chokes?
Generally, I've always considered that you are too lean at idle if RPM rises when you put the choke on. Though looking at the choke circuit on the PWK28's on mine, it seems to bring air through as well. Though in my case, it seems to be too much and the bike would sit on 5k rpm if I left the choke open all the way.

I'm only on 40 pilots, so I'm going to up those to 45's anyway but I'd like to hear others experiences with their chokes so I know what to aim for.

Edit: Also where are you all buying your PWK needles from? Looking for N68A, but seems I have to buy a pack of 4 mixed needles to get one. So need to buy 4 packs of 4 to get my 4 needles.

[Luther]

Good to see you climbing back on the bike Hybrid!
There seem to be PWK 28 needles that came stock in 85 mx bikes but aren't on generic parts lists, don't have searchable numbers because Honda, Kaw, Suz, Yam. You can measure the top diameter with a micrometer. If the taper is too close to tell by eye you can open your dial calipers to a number like .085" and drop a pair of different needles between the jaws to see where they stop lengthwise. It help in knowing where throttle position is on the needle. One thing I have noticed is that if you get the needle and needle jet to a point that its too lean but its running good otherwise the bike will slow down more quickly or abruptly as you close the throttle from accelerating. Richen that back up before you damage it. Some other jet is making you want to lean it down. The opposite situation was pointed out early in this post. Cruising in top gear for a few miles at say 5000 rpm and it starts loading up till it fouls plugs or you quit cruising and use throttle and shift gears a while. The plugs are back to brown when you check at home later, makes you wonder how it could be rich enough to sputter earlier.