Topic: 400f jets

[dugsgms]

So, after struggling with a stumble when coming off closed throttle and running around with a wide band sensor, I'm fairly certain that both my main and slow jets are too large(I live at 5000 ft and do most of my riding between 5000 and 7000 ft). I'm looking at 72 mains and 38 slow jets(currently have the stock 75s and 40s). Only issue is that real Mikuni jets are getting a bit tough to find, anyone have any experiences with aftermarket jets(looking at ones from 4 into 1)? Any opinions pro or con?

[Bodi]

First, these are Keihin carbs so Mikuni jets are not a good choice. Beyond not fitting, the numbers have very different meanings.
Next, aftermarket jets are notoriously unpredictable. A counterfeit 72 might be richer than a Keihin 75.
I would try dropping the needles a notch or two. And make sure the emulsion tube crossholes (main and pilot) are open and clean - blocked or dirty equals richer. You can also drop the float level and get a bit leaner.

[dugsgms]

  Oops, your'e right, I meant Keihin, had RD350 on the mind(hey, at least I didn't say Amal). I certainly will pull the pilot jets and the emulsion tubes before buying anything but seeing as the stumble goes away when I ride down the mountain I kind of think the #40 pilot jet is a bit much for the altitude I ride at but your'e right, better to check before buying parts I don't need, thanks.