1987 xr200r tuning

[riverside21]

Recently picked up a 1987 xr200r in pretty good condition, all stock.  The carb was all gummed up and running real rich, and the previous owner removed the baffle and end cap from the exhaust, but left the air box top chute in place.  I cleaned up the carb and verified all stock jetting, needle position, air screw, etc.  Where we live the quieter the better for off-roading so I ordered a new baffle and end cap, but did ride the bike for a week before the parts arrived.  With the muffler parts out I had a brown plug and plenty of power throughout the entire throttle range.  Got the muffler parts, installed them and now the bike falls flat while climbing hills and gradually rolling on the throttle, I get a burble at low speed sometimes and I have a black sooty plug.  I'm kind of at a loss on this one.  I realize that the parts restricted the exhaust....but it's basically back to stock and I've had these bikes stock before and they ran fine.  Seeing as I have all stock jets and am getting a sooty plug, I'm wondering if electrics are weak?  I also tried adjusting the air screw in/out and moving the needle clip to position 2, either of the two made my problem worse.

Any ideas?

[riverside21]

Thought I'd post my findings for any future readers.....

My final problem turned out to be a worn needle & needle jet.  My carb kit contained a wrong size needle jet (fit loose in the body) so I didn't install it.  I read another similar post here on TT about a guy having some rich running probs and a Honda parts man told him to change the needle and jet.  I ended up finding a NOS needle/jet kit on Ebay and installed that - instant fix and now the bike has a tan plug.  

[Chuck.]

Yes the needle and needle jets do wear. And exhaust systems do change jetting.  The needle and needle jet kit isn't listed for early XR200R so buy the late one, but avoid the CA version.

Part Num 16012-KT0-A10, CA version is 16012-KT0-L00