Pity about the rain on the weekend.
I'm still scraping the baked on clay from the 495 and attempting to wash it all into the garden...
I managed to bump into Brad Lewis on Sunday morning and I picked his brains about all things KTM.
I must thank him for his time and the advice he gave me was greatly appreciated - a truer, more knowledgeable gentleman I've not met.
He confirmed what Adrian has spoken about in relation to running-on - it's a 495 trait, but it can be lessened.
That massive lump of a piston swinging up and down in that bore makes for a very good air pump and the consequent vacuum will lift a Bing slide, causing the engine to run-on even after you shut the throttle.
The fix is to weight the slide with epoxy in the choke-slide cavity and pre-load the spring. That makes the slide shut properly and prevents the engine vacuum from pulling it up.
He also suggested a couple of other fixes (I hope I'm not giving away trade secrets here, and if you know all this already, well you can stop reading now...)
Chamfering 2mm off the rear of the slide will help to reduce any lean-bog as you crack the throttle out of a corner.
That chamfer will have the same effect as an accelerator pump and will draw fuel through the needle-jet at that very small throttle opening just off idle.
It will not have any effect on things as the slide opens further as air will still flow under the slide as normal at wider openings.
ATF in the gearbox should help stop clutch creep, and cutting the clutch push-rod in half and adding a suitably sized ball-bearing in the middle will prevent the push-rod from galling on the end whilst trying to turn against the clutch plate bearing when you've got the clutch open waiting for the gate to drop...
And, as an aside, Brad has experimented with all the different brands of carby and keeps coming back to the Bing for outright power - only a 44mm Mikuni with a power-jet will come close!
He confirmed my current jetting settings and basically said I was on the right track. Apparently the bike will tell me what it needs and only experimentation on one's own machine will produce the best results.
Anyways, thanks for the help on this subject from everyone else, I'm off to the shed for some more cleaning/fiddling etc.
See you all at the Classic in August.
