Aftermarket carb diaphrapms

[Flynt]

Hmm, took a better look at these in contrast to my old diaphragms and slides today. The new ones have are cut away at their base, while the old ones are flat. Will these slides work?

The curved bottom slides are the newer style and likely work better, esp at part throttle around town...  I think they make the carb throat smaller, increasing low/med engine speed air velocity and vacuum felt by the main jet.  The emulsion tubes for the curved bottom slides have a 180 degree shroud around the hole the needle goes into.  This shroud goes toward the carb intake and (likely) also increases the vacuum felt by the jets at low engine speeds.  It could also be that the curved bottoms and shrouds help with transition onto the mains.

My '84 came with the flat bottom slides and the shrouded emulsion tubes, fitted by PO along the way.  It worked ok, but I went to un-shrouded when I tuned the carbs.  Now it runs fine with the flats/no shrouds...  not sure if curved and no shrouds would work, but they should IMHO.  Might require some jet/needle tuning...

Frank

[racerrad8]

The 1100 main jet needles for the flat bottom diaphragms are also different than the curved bottom main jet needles. They are approximately 4-4.5 mm shorter than the stock main jet needles for the 1200 curved bottom.

Robert - RPM

[azure]

Thanks to you both, Robert and Flynt. Robert, i will order those mains and emulsion tubes from you when I get back from my travels in the middle of January.
Happy New Year, Guys!