What have I done (wrong) to my 24mm PWK?

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dansuper
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Sun Feb 06, 2011 11:33 am

Disassembled my carb yesterday (it's an OKO) having received some advice from forum members on PWK clones and potential modifications. My main issue was a boggy spot at 1/4 throttle, which seems to be the norm. I was also going from lean to rich with minor changes (1 clip position) so this was a last gasp effort before trying something else. :?

The mods are to drill out a couple of passages for better flow, but it turned out my carb was already at the 'should be' spec so there was nothing to change. But after reassembly, it has a weird issue. It will start and idle, but just off idle and thru mid range it basically cuts out as if it's flooding massively. If I can coax the revs up over the 3/4 position, it keeps revving out but as I roll the throttle back it you can hear it dieing as if the kill switch is hit.

I also thought it might be the opposite - a fuel flow blockage rather than a flooding issue, but I pulled the plug and it seems really wet so have ruled that out.

Don't have compressed air at home, but have stripped and reassembled the carb three times with the exact same problem. Float level seems fine. Can blow thru the jets.

I'm running a Casa 185 with a KBA Clubman - and am contemplating alternative carbs, but would still like to get the PWK working again... before binning it for a Delly or Mikuni... :?

Thanks in advance,
Dan

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dapper
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Sun Feb 06, 2011 12:59 pm

Dan, I'd buy an aerosol can of compressed air (air dusters their called). Just next to your main jet is a tiny hole which is the pilot jet. Remove the brass pilot jet from underneath and use the air duster to blow through the hole. When you look down through where the slide goes, you'll see the main jet and pilot jet just next to it. Get a bright torch a shine it through the pilot hole whilst holding a finger over the main jet to block the light. By moving your head or the carb about to get the right angle, you should just be able to see a tiny bit of light through the pilot hole. It's so small that it's easy for it to get blocked. I take it you've already checked the two holes where the float valve goes are the right size. You may also benefit from drilling a 1mm. hole into the bottom of the rubber carb hose as the spitback can collect here and cause over rich starting. Can make a mess of your runner boards though.
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coaster
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Sun Feb 06, 2011 3:40 pm

All good advice from Dapper althoug a can of carb cleaner is also good for blasting jets and passage ways and maybe a bit easier to source.

Have you made absolutely sure that your choke is turning off completey ?

Your original problem could well be that you need a leaner needle, the ones supplied with them are seldom ideal.

martinr
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Sun Feb 06, 2011 4:01 pm

did you remove the long brass bit up the centre of carb that the needle goes down and the main jet screws into . if you did are you sure the small brass bit that sits on top of this has gone back in the right way

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dansuper
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Sun Feb 06, 2011 10:42 pm

Thanks for the tips everyone - will pull it down again and try the carb cleaner and / or air as soon as I can.

Martinr - I did remove the main and atomiser (the long brass tube?), but don't remember any brass bit on top of that - can you let me know from the diagram below which part that bit that is? Does it sit loosely or screw in?

Thanks heaps,

Dan

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MarkH
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Mon Feb 07, 2011 5:30 am

It's pretty easy to f@@k up the float when reassembling the float bowl. Check that you haven't bent the tab or anything like that.

martinr
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Mon Feb 07, 2011 1:26 pm

hi dan. its no34 on pic it sits loosely on top of atomister till atomiser is screwed in place .if you look down carb mouth from the front you should see it sticking up about 5mm

shocky
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Mon Feb 07, 2011 2:13 pm

i agree with mark its very easy to bent the float tab when taking the bowl of take the bowl off with the carb upside down
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C*NTSPEED
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Mon Feb 07, 2011 4:01 pm

if you need jets or needles give allens a ring :roll:
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dansuper
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Tue Feb 08, 2011 3:56 am

*Mark and shocky* - thanks, yep, learnt pretty early on that that the float bowl wasn't going any where unless the carb was upside down. I can see the needle seating as the fuel flows to a certain point below the top of the bowl then stops sudnely - I'm pretty sure the float is at the 22mm mark, too.

*Martinr* - hmmmm, distubingly I never remember seeing that part when removing the atomiser previously! Maybe it was just 'stuck' in? Will check to see if it has fallen out during reassembly. :oops:

*C*NTSPEED* - is 'Allens' a UK reference? I'm in Sydney. ;)

Cheers!

(So, once I make my way through this and it still doesn't work - 25mm PHBL or TM24? I have knowledgable friends arguing for/ against both sides. :geek:)

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