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PWK Carb Adjustment on a 1000SP
Ratso88:
--- Quote from: monkeyodeath on April 30, 2025, 12:04:44 AM ---Having better luck with the carbs, but I'm noticing a "gurgling" sound coming from the left cylinder area when I shut the engine off. Does anyone know what this might be?
--- End quote ---
Could be fuel in the bowl boiling off. ???
Just a wild ass guess, really.
someguy:
--- Quote from: Ratso88 on April 29, 2025, 06:31:47 AM ---The PWK is a 2 stroke carb.
--- End quote ---
While this is true we used to run the "OEM" ones (not the clones) on our small bore 4 stroke race bikes with very very good success. But they were small 26mm IIRC.
IMHO getting the throat size right for the displacement is the key.
SemperVee:
Might just need a complete and thorough cleaning..
monkeyodeath:
Just wanted to update this in case it helps anyone else...
As is so often the case, the answer was to clean the carbs AGAIN and then go ride the bike hard.
I think there might have been a stuck ring issue or some shmutz in the carb or fuel line, but it's cleared up now.
Managed to get the carbs pretty well-balanced with a Carbtune manometer.
This is my first Guzzi, so I can't really comment on these carbs and how they compare to the Dell'ortos...but they seem to run really nice all through the rev range. Throttle pull is very reasonable and choke is barely needed to get 'em going. A little popping on decel and I might try Mike's recommended idle jet size to see how that gets on, but otherwise, so far so good.
The PWKs do seem like a pretty common carb on all kinds of applications, and appear to be a drop-in for Amals, so fairly popular for British bikes. They are available from Keihin, but there are also tons of copies out there from various companies, in sizes that Keihin never even made. Fit on the 1000SP is pretty great, super-easy to remove (stock airbox was removed by PO, so just running pod filters). Mine are the 30mm size. Confusingly, I'm not sure if Keihin themselves actually made a 30mm PWK, but I've found that most of the parts are interchangeable between all of them if, like me, you're clinging to your old Sudco catalog to reference parts when trying to find them elsewhere (RIP Sudco!)
The carbs on my bike are almost certainly copies -- the Keihin logo area is visible but ground off -- but they seem to be of decent quality aside from a little rough casting in the float area around the overflow drain -- no big deal. The idle mixture screw on one of them was a bit loose, so I bought a genuine Keihin rebuild kit and the included mixture screw and spring worked much better.
Adjusting the idle mixture screw on the right-side carb when it's on the bike is a little tough for tuning while running, so I just set mine at Mike's recommended turns and since that seemed fine, I left it alone. You can buy idle mixture screws with attached knobs that would make it much easier to adjust them if you wanted.
Chokes are currently on each carb, which requires a little hand-switching to turn them both off, so I might someday consider a remote choke kit.
So, despite nominally being a 2-stroke carb, seems like the PWK works just fine on a 4-stroke. As far as the aforementioned FCRs... I have those carbs on a Ducati 900SS and they are pretty sweet, but I do wonder how much, if any, I'd gain by going with them, especially considering how much they are and that the 1000SP heads might not have much more to give without some serious reworking.
At first I was put off by the fact that these PWKs were knock-offs, as that's not usually a route I go, but as I said, castings looked alright and I can't see anything noticeably crappy about 'em so, it might not be as bad as it sounds. Probably better than some knackered ebay carbs.
At the very least you can still buy genuine Keihin seals, jets, floats, and float needles, so if the casting is good it's possible to upgrade everything else to quality parts.
Thanks again for the advice for this new Guzzi owner!
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