I'm posting this as an update... and an FYI.

I've encountered the same damn problem.... (on dirt roads, not just flat dunes)
The DS just starts slowing down when I've got it pinned tapped in 5th. But not right away... only after about 2+ miles of WFO throttle. SOoooo... now that I re-read the messages back to me, and that I said I'd try a leaner main... I'm gonna finally try it. [img]i/expressions/face-icon-small-happy.gif[/img] But coming from 2strokes... a leaner main is scary to run WFO.

Just thought I'd give ya all a shout and say thanks for your help too!!!

I've asked... but don't remember this either, but is there a direct bolt up carb; that's not - A, vacuum... and B, for a mostly stock motor?? I want to get rid of that carb as I don't know them too well. Plus... it seems it's very finicky.

Lemme' know!

 

try a lower main for sure,, that is way to big---- 170 or 172.5 maybee

 

Way to rich, I would try a 175 or 172.5 as earlier mentioned.

 

Mine was doing the same thing but would come and go. I modified the tank vent and drilled the petcock. Then I drainied the tank to see how much flow it was getting-not much, the filters were plugged with a weird film that I still don't know what was. I yanked the stock filters out of the tank and put on an iline filter and have never had another problem.
You could try seeing how much flow your petcock is putting out.

 

Hmmm...

But to 'know' how much 'flow'... I guess I could compare it to my other bikes.
But it doesn't seem that it's less than 'normal' whatever normal is.

I only know this from when I drain Mexico gas from the tank.... and it takes a while.

I'll check flow to my XR650... and then also change to a smaller main, starting at a 180, then 175...etc. I'd rather not be too lean due to my riding style. But ya know... the more I think about it... the more I realize I get CRAPPY gas mileage outa my 5.5gallon IMS tank compared to some 2wheelers I ride with. However... I am hauling 150+ more pounds of metal and plastic than those bikes too! [img]i/expressions/face-icon-small-wink.gif[/img]

Did I say it yet...??
I love my DS!!!
And I ride mostly 2wheelers!!!