vegansydney wrote:I've been toying with the idea of fitting a 24mm Polini PWK on a GT186 after I found a TM24 (my carb of choice) fouls the engine mount using the manifold, and my welder suddenly moved out New York with the pandemic. (FYI a Polini PWK 24mm won't foul on a GT 25mm manifold).
In my research I found that GSF has a wealth of information, including that the
Polini needle table differs from the KEIHIN needle table, genuine Keihin and
KMT jets appear to be the only ones made to spec, not even Polini and BGM are correct. Like other PWK clones there have been
reports of fuel flow issues with the the Polini.
Good luck, and please keep this thread updated. For now, I'm going to find a new welder and stick with the TM24, which is a shame because the Polini come in such a diverse range of sizes, and they're not an antiquated roundslide that UK tuners seem so infatuated with
There is some good information there, although Polini would appear to have issues with quality control. That is extremely disconcerting, especially when their manufacture of complete Paramotors is taken into consideration. The fact that Polini are a major supplier, predominantly to the race scene, with Polini only race series, must surely ensure that any quality issues will be addressed.
I've had PWK's from Koso, OKO, Stage6 & even a Chinese copy. It's fair to say the first three are very good out of the box whilst the Chinese replica needs more attention. But for ten quid?
Personally, I endeavour to follow my own advice in trying to select the most sensible guides from various sources.
Primarily, regardless of manufacture, any carburettor should be stripped to it's component parts & rebuilt, blueprinting as necessary. That instils both knowledge & confidence.
With any PWK, the float angle is critical, though not difficult to set.
The fuel feed to the float needle should be checked to the recommendations available on line. Kerist, the PWK has been around so long now that that Scooter-Tuning-Legend-in-his-own-Lunchtime (you know! The one that invented the wheel!) has PWK fuel feed modification data on his website. Other websites are available such as that from Mid-Atlantic Trials etc
The bowl has a float bottom stop which I remove with an electric sanding file.
As for jetting & needles, there will be variances between manufacture, but I reason that if they are bought in a set of ranges from one source, it doesn't matter a great deal because they will be used as comparators with one another, not with jets, say, of another manufacture. In the case of needles, I am fortunate to have Keihin, but even they do not conform with their own charts. But Hey Ho! I use them as comparators so see even that as fly sh1t.
The German owner/rider/tuners are heavily into the technology of tuning & their 'warts & all' responses are refreshing, with some knocking Polini, rather than the "Hail PHBH round slide four stroke derivative carburettors modified for two stroke use & all who use them!" mantra that predominates here. Incidentally. Google Translate came up with the word 'wischi-waschi' which amuses the likes of me. A lot like (so I'm told! Don't shoot the messenger!) the Welsh word for computer is 'computor'
As I said earlier, I doubt Polini's problems will be around for long. What has inspired the Germans is the principle with some buying into the Keihin PWK's. Hardly surprising, I suppose, as they have been OEM supplied on the best Japanese 'crossers for years. In fact, OKO PWK are also original equipment on quite a number of trial bikes, I believe.
Change is often quite frustrating. There will be people that want the individuals that try alternatives to fail.
The Scootering fraternity does tend to take comfort in many of them having a lot of the same things, & I can see the logic in that. But that ethos is sometimes flawed. Take the example of electronic ignitions fitted because 12v points based systems are 'unreliable'