as written above, for me it`s just a theory. If the engine runs lean at high rpm you will have sudden power loss. I experienced that on my Gilera when trying aftermarket exhausts without rejetting.
If it runs too rich problems I think are similar but less abrupt and combined with more exhaust smoke.
reading about the problem Harry has would indeed indicate on a too lean mixture.
Still I wonder if the engine gets enough air when driven w/o airbox as the carb is standing so upright. I`d love to know about any effects using a backplate on the filters or to different jettings. So guys keep posting your results.
Although jetting is probably best adjusted on a dyno I think using open filters will definetely require some driving tests as I don`t think the effects of the airstream at high speeds can be properly simulated in a shop.
I personally always drove with an airbox and will stick to that also if it`s a lot of work building one.

G.

Hi Guys, Thanks for all your suggestions and advice. I have been running premium unleaded in the bike (98RON) and then I read somewhere the other day that you should be running the lowest RON grade you can without the bike pre-igniting. So last weekend I filled her with standard unleaded (90RON), took her for a big blast making sure I reved her nice and high and all of a sudden I noticed the flat spot and spluttering started to disappear. By the end of the ride she was running beautifully. I think the combination of fuel and a nice hard ride really cleared her out. I would however still like to fit an airbox to see what happens. Does anyone know where I can find a link to someone that has done this before to a 906 with Mikuni carb mods? I'm keen to experiment...

http://forums.ducatipaso.org/viewtopic.php?name= ... cle&sid=29

this is on a 750 showing the most simple solution modifying the original airbox. The negative part is that it loses volume so I`d say a K&N filter becomes mandatory.
The original carb jettings from a SS or also a Dynojet kit may be used as starting point for rejetting.
Recovering the lost box volume is difficult unless you create your own construction.

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