Skywatcher wrote:Hi Arkie
On these carburetors, there are three different materials used for the pump diaphragm, neoprene, Mylar and fiberglass. Mylar can be blue, black or clear, neoprene is always black and the fiberglass diaphragms are brown with a weave pattern. If the face of the carburetor is machined to a mirror finish, then the Mylar or fiberglass diaphragm should be used. If the face of the carburetor is as cast with no machining, then the soft neoprene diaphragm must be used in order to form a seal against the cast face. Hope this points you in the right direction. All the best,
Sky
This carb does have the polished very smooth surface.
I just happened to accidently stumble onto this and the carb would have went into my carb salvage bucket if the nylon type had not been in the kit. I had put a china clone carb on the unit and got a good idle but a rough full throttle and the H jet no adjust (bad clone) but the new looking engine & Walbro would not even get a start due to flooding immediately.
The pump side of the carb tested good using vac/pressure and the nylon reed flapper just happened to be handy from the kit when I removed the reed side to inspect so as a one last attempt I installed it and was surprised when I got a run. I took the carb back apart and carefully inspected the reed flapper holes and the rubberized reed and same thing again. Re-installed the nylon one and A-ok.
If the carb had not been really user friendly to remove/re-install and test it would have went to my in my carb salvage bucket fast.
I searched on-line for any info about using the nylon or mylar and no info but did see a video of a guy installing a kit in a WT827 carb and his Walbro K20WAT kit DID NOT have the nylon type diaphragms, just the neoprene type.
Maybe Walbro just started adding the nylon type pieces to their later kits??Will have to keep a heads up on this one when doing future carbs.
I'm wondering now if a guy could use a flat surface such as a piece of glass and 1200 wet/dry and lightly break the polished surface and get a good run using the neophrene rubberized type when the mylar or nylon is not in a kit as a last step attempt at getting a good run?