Carb Icing?

A reader of this blog commented that his Alp 4.0 suffers from rough running after some time at speed on longish (say 200mile) journeys. Here's what I think:


I have had bouts of odd running on some of my longer journeys but I have tended to feel it was rain in the petrol/airbox/electrics. 18 months ago on my return from the Stella Alpina (as I wrote in my blog) I drained water from the carb bowl and then a little petrol. No wonder it wouldn't run! Of course, on such trips you do tend to run close to the bottom of the tank. I also think it runs a little lean and perhaps at speed the cylinder is getting cold and mixture a spot weak? Altogether I've never found it a totally smooth runner...

I suppose I'm discounting carb icing as such as I've not heard of it as a DR350 issue and the carb/airbox/head is straight off the Suzuki. However I suspect it is jetted a lot leaner than a DR to get it to Euro regulations - really it is a very low tech motor to be still legal! one day I suppose I should find a dyno and get it jetted properly, which I'm sure will be richer.