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Dropping the needle will lean it out. If you think it’s lean, drop the clip and raise the needle. The little hesitation you describe when you crack the throttle, sounds like a temporary lean bog (that’s the condition the accelerator pumps can cure - they squirt extra gas at that point.)
You can play around with bigger idle jets too as they do have an effect. Going a bit bigger won’t hurt starting / idling.
Plug chops don’t tell you much aside from mixture at WOT. I’ve never tried doing one on a four stroke but if you do, you need a new plug, pop it in and load up the engine in 4/5th gear, flat out, uphill. Cut the engine when you’re flat out and coast to a stop clutch in. Take the plug out and ride home on a spare.
I find it very hard to read the mixture without cutting off the threads but you’re looking for a solid brown ring about 2mm up the base of the ceramic insulator. Black or much higher is rich, less or feint is lean.
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Jung
@pdlouche
Think I might try tinker the carb on the DR. Haven’t touched the setup for a year or two and have just been riding around the issue. DR has a TM33 without the accelerator pump, so effectively a flat slide. Larger bore, aftermarket can with baffle. So, it has a bigger capacity than standard and could be lacking in back pressure compared to a heavy stock can.
Having tweaked the air/fuel and idle, it starts on the button and idles beautifully. No hunting, no risk of cutting out by dropping too low then rising again.
When riding, from anywhere from half to WO throttle then closed, there’s popping on the overrun.
When riding there’s a hesitation at mid rev range. You can turn the throttle super slowly and just about ride around it but it is there. Definitely there if hard crack open.
So:
Popping means lean on the idle circuit. I don’t want to increase idle jet at risk of upsetting starting or idling. However might be the only option here?
I tried a number of main jets before and it just moved what revs the hesitation happens.
Finally now, I might just try to drop the needle (raise the clip). If that is enough to adjust the fuelling, and smooth out the delivery, maybe it resolves the point where it hesitates from getting too much fuel?
Alternatives would be an even smaller main jet or a bigger idle. I guess at this point a bigger idle jet is the most sensible test, since the main jets didn’t help.
Need to do a plug chop as well.
….
Thing is under load, on the lanes, I’m sitting below 6k all the time and it drags me along fine. But it feels like it’s dragging me along. If I open the throttle quickly at 3-4k it putputputpuuuuts its way up to 6k. Above 5k so long as you’re above the point of hesitation, you crack the throttle and it revs up fast like you’d want.
Clearly I’m riding it at the lowest throttle getting that bit of low down torque, but the transition from the low down torque into the (limited) peak power at 7-8k is where I want to be able to lighten the front, and the hesitation is bang in that zone.