Originally Posted by mcma111
Hey DR guys. I usually hang out over on the Honda XR650l side of the fence but my buddy has asked me to look at his buds DR650. Looks like a late 90's model. Yellow fork boots and blue/purple frame.
The engine will start and idle but will not take throttle. Once the throttle is twisted some it will rev a bit and then fall on it's face, not accepting throttle. It's my guess that the diaphram in the carb is bad or leaking and not allowing vacuum to lift the slide.
What say you DR guru's?
Could be the diaphragm but I'd bet on the Pilot Jet. With your experience you should have no prob pulling the carb off and giving it a good clean.
Sometimes grit hangs up in the small Pilot Jet passages, has to be 100% clean to run well.
Parts in the BST Carbs do wear out over time. Slide, Jet Needle. Also maybe pull the needle jet in the float bowl, check for debris and make sure rubber tip is firm and sharp.
Sometimes its cheaper to buy a nice used, low time BST Carb and just put that on. Good luck, hope you get her up and running!
MCMA? I used to be a member in the early 90's. I hear the property is looking good with new trails. Great group of guys!!