PWK card throttle sticking.

[7iain7]

I have fitted a 28mm PWK carburetor to my 1952 plunger. However, the slide spring seems a little too weak, which is causing the throttle to stick sometimes. I am wondering if anyone else has encountered this issue with the PWK carburetor. I am aware that there is a stronger spring available, but it is difficult to source.

Many thanks,Iain

[muskrat]

G'day Iain.
Having two on the Cafe I wouldn't want heavier springs and haven't had one stick.
Are you sure it's not the cable or routing of it?
Cheers

[7iain7]

Thank you for the reply. I'm fairly confident (but not 100%) that it's not the cable routing. I've been playing with it for a few days now, and the throttle snaps back when released. One thing I've noticed is that there is already quite a lot of scoring on the slide bore. I bought a PWK28 (£25) new from eBay, and that may be the problem.

[muskrat]

G'day Iain.
That may well be the problem. There are a lot of cheap Keihin PWK knock offs out there, some better than others. Mine aren't proper Keihin (has the flange glued on (now removed)) but cost ￡80 ten years ago! A genuine Keihin will cost about ￡200
Do you have an insulating gasket (tufnol) between carb and head? May be distorting when hot.
Cheers

[7iain7]

I haven't fitted an insulation gasket as its quite tight fit, but will look into fitting one.
I've made a flange mount that goes over the spigot as shown in picture.
(need to tidy the pluming)

[muskrat]

G'day Iain.
Mine came with the flange fitted. Same as the JRC kit. I removed them to use rubber spigot mounts as I was worried about fuel frothing from vibration. Thinking of going back to flanges (lost originals in the fire) so will have to make new manifolds and flanges. 
Cheers

[Magista]

I have the JRC/PWK on my A7.

Recently I experienced a sticky slide issue and had found brown residue on the slide. It ended up being old gas my friend brought me when I ran out of gas on the side of the highway. I was also told old tank liner will cause these issues as well. Once the gas was replaced with the non-ethanol I usually run, the bike ran fine.

As for the stronger springs. I bought two from a supplier in Japan because I felt the stock spring was too soft. I installed the heaviest one. To me, it feels much much better and is snappy and responsive. If you like I can DM you the link.

Something else to consider, may want to get an exit tube with a bend in it for the throttle cable. The straight cable may be hanging at the bend on the carb cap.

[7iain7]

Very interesting because I have almost the same issues.

[rocker21]

if you want stronger springs, contact me as i import the JRC carb into the UK and keep a fair selection of parts.

[7iain7]

Sorry for the late reply.
I've sorted the issues now.
It good to know where to get spares from.
I'm very impressed by the PWK carb.

[rocker21]

The real ones work well, the Chinese copies are rubbish, they are cheap and look the part