Jawa Flat Twin

[Luca]

We're fortunate that we get to adjust our idle mixture at all.  I've gone over a number of carbs (some of them contemporary with our R65's) where the mixture screws are either behind a lead plug or have the little tabs on them so they interfere with the carb bracket at about a half a turn.

The VN750 I owned had the lead plugs over the screws.  The factory manual called for them to be replaced after the carburetor had been reassembled.

[Barry]

We're fortunate that we get to adjust our idle mixture at all.I've gone over a number of carbs (some of them contemporary with our R65's) where the mixture screws are either behind a lead plug or have the little tabs on them so they interfere with the carb bracket at about a half a turn.

Too true.

Before gas testers came into common use there were some devious methods of achieving lean idle mixture settings before fitting the anti tamper cap. One was to set it lean enough to drop the idle speed by a calibrated amount as observed on a tach. Another was to set it to idle perfectly while the mixture was being artificially enrichened by injection of propane gas. When the gas injection was removed the mixture was effectively leaned off by a set amount.  In mixture terms they were a far cry from setting it mid way between the stumble points.

I don't go as far as seting the mixture so lean that it actually lowers the idle speed but I do lean (sorry) in that direction and get it as lean as it will go without reducing the idle speed.