Bike idels and starts ok but stumbles when throttle increases

[Mark19]

Help 1980 XS650 Special II

This has been a long project. The bike starts and idals ok but stumbles and backfires when throttle is increased.

Recently replaced stator,battery, coils, wires, plugs, regulator, fuze box, and brushes.

Bike was running well.Drove it on a 400 mile (5.5 hour ride in 80 degree heat) Engine got real hot in traffic. Half thru trip the engine started backfireing on acceleration and stumbling. Also noted loss ofpower when signal was turned on.

Came home from trip and replaced plugs and inline gas filter. Bike ran ok for 20 min and started again. Took of carbs and looked for dirt. cleaned carbs and reassmeled. Bike is still doing. Looked at the forum and two things looked simular. Blocked jets and advance rod sticking. Not sure where the advance rod is. Dont know what else to check in carbs. Need help Thanks.

 

[mouser]

take the fuses out of your lighting circuits and see if it still does it. You don't have an advance rod on your bike. Your advance is controlled by your ignition module under your battery box...The dreaded black box. You might want to read a recent thread of mine.
"my bike starts,runs,idles perfectly but will not rev"

 

[bergoff]

Did you check to see if your carbs are synced? Mine did the same thing until I synced mine.