Rebuild Ducati Mikuni BDST Flat Slide Carburetors


| 2/17/2017 12:00:00 AM


Tags: March/April 2017, How-To, Ducati,

 

This How-To might seem a little out of sync with our mission, focusing as it does on a 1992 Ducati 750SS. The name of the magazine is Motorcycle Classics, we hear you say, so isn’t 1992 too new?

Believe it or not, it’s been 26 years since Ducati introduced the 750SS for the 1991 year, putting it just inside our general policy of only featuring bikes 25 years old or older. Hard as it is to accept, 1991 was, well, a long time ago. In the motorcycle marketplace, our project 1992 Ducati is just old. It’s at that awkward age where it’s neither fish nor fowl; somewhat ignored by lovers of more vintage machinery yet too outdated to be interesting to riders looking for modern hardware. It is in fact a potential bargain Ducati, perfect for riders who appreciate the brand and its heritage.

An updated version of the 750 Sport of 1988-1990, the 750SS featured improvements over the outgoing 750 Sport including a wet clutch — the first Ducati so equipped since the Cagiva Alazzura and Elefant — and a pair of 38mm flat slide Mikuni constant velocity carburetors in place of the 750 Sport’s troublesome single Weber. The Mikuni swap yielded improved performance, with none of the flat spots or hesitation experienced on the Weber-equipped 750 Sport. But with the youngest Mikuni-equipped bikes now 20 years old (fuel injection came in 1998), the likelihood of one of these bikes needing a carb rebuild is high. BikeMaster

Fortunately, Mikuni BDST flat slide carbs are easy to rebuild — even on a Ducati — and parts are readily available, if you know where to look. Surprisingly, the same sources that don’t list kits for the 750SS do list O-ring and float needle kits for 1992-1993 Yamaha TDM 850s, which used the same 38mm Mikuni as the Ducati 750SS. Going to eBay and typing in the search term “1992 Ducati 750SS carb kit,” we found a few vendors offering kits that included not just the O-rings and float needle, but all new jets, the slide needle and the atomizer tube. Those kits ran in the $52-$56 range (per carb). In the end, we opted for O-ring and float needle kits from Power Barn for $32 each.

We should note that this was not a comprehensive rebuild. Rather, it was sort of quick and dirty, to see if we could get this 750SS running again. Which we did, and quite nicely, thank you. Although we did not soak the carb bodies, our subject carbs cleaned up well using spray carb cleaner followed by compressed air to chase the orifices. If you do soak them, make sure not to soak any plastic parts, cleaning them individually instead.




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