Acceleration Issue

[2wheelgypsy]

I bought a 2003 dr650 with low miles(5000). Bike ran fine at first but then i started experiencing a jerk and then a popping sound out of the muffler while accelerating. I'm wondering if that has anything to do with the carb? The bike was purchased at 800ft of alttitude and i currently have it at 3000 ft. Now it is doing it a lot more. I adjusted the valves, changed the plugs, and changed the oil. It went away for a while but now its back. Any info would be greatly appreciated thanks.

[mxrob]

I bought a 2003 dr650 with low miles(5000). Bike ran fine at first but then i started experiencing a jerk and then a popping sound out of the muffler while accelerating. I'm wondering if that has anything to do with the carb? The bike was purchased at 800ft of alttitude and i currently have it at 3000 ft. Now it is doing it a lot more. I adjusted the valves, changed the plugs, and changed the oil. It went away for a while but now its back. Any info would be greatly appreciated thanks.

Popping is generally caused by a lean condition. A dirty pilot circuit from the bike sitting (or just out of adjustment) can cause this. Also the BST has a plastic spacer that the jet needle is suspended and positioned by. This spacer is known to wear allowing the needle to drop further into the needle jet leaning out the engine further than it already comes from the factory.

[2wheelgypsy]

Hey Rob thanks a lot for the response. Wanted to get to the bottom of it before I kept spending money. I guess ill have my buddy rebuild the carb. Again thanks a mill for the advice. Great forum.

[donwann]

It shouldn't be running lean with the increase in altitude. It should be running a little rich in fact. I wonder if the bike was sitting for quite a while before the purchase and gummed up some of the jets/passages inside?

[stu5969]

I would also check the inline fuel filter, it's at the carb end of the fuel line, PIA to get out, you'll see a small white ring on fuel inlet to carb, that's it. Back it out carefully, fragile little bugger. I would also check the fuel flow from the petcock while apart also. The vacuum ones from the factory aren't the most reliable thing. Should have no flow in ON or RES, without engine running or cranking, and a strong flow on PRI. good luck.