Hello and thanks in advance for any help.
USA VA, 30 ft above sea level 50-70F.
I recently purchased a 2012 dr650 in close to stock condition with 5100 miles. I added FMF power bomb, Pro Cycle silencer, Opened air box, K&N air filter, Pro Cycle jetting kit (150 main). I removed stock fuel filter and added an inline filter.
Tried the 3rd (from top) clip position and way to lean. Massive surging. Needed near WOT to pull cleanly.
Tried the 4th clip and much better, but still lean (surging, lack of throttle response) at low throttle openings (<3/8).
Now I'm on the 5th clip position and it was
running very well. Just a crack of the throttle to cruise at 65 mph.
After a about 10 miles, it started running lean again at partial throttle openings, and required much more throttle to cruise at 65 mph. I thought it may have been nearly out of gas, so I filled to the top (2.5 gallons). May be my imagination, but it seemed to run well again, but after another 10 or so miles, was acting lean at low throttle openings again.
I've had a lot of experience with Keihin PWK 2T carbs, but this is my first carbureted 4T. On a PWK, it would be the slide cutout acting in this throttle range, but there don't seem to be specific circuits to tune on BST. I'm also puzzled why the fuel/air ratio would seem to change during a ride unless the engine was getting very hot and leaning out.
Next time I ride, with a cold engine, I'll see if it runs well for a while, then goes lean again. That would lead me to suspect a heat related issue.
Any ideas, thoughts, suggestions where I could look to diagnose this?
Thanks again for any help!