Throttle stumble just after idle

jpdevol

XS650 Junkie
Top Contributor
XS650.com Supporter
Messages
725
Reaction score
1,463
Points
143
Location
26187
Did you verify ignition timing?

Also, what is the power source for the XS Charge ignition?
 

jpdevol

XS650 Junkie
Top Contributor
XS650.com Supporter
Messages
725
Reaction score
1,463
Points
143
Location
26187
yes sir! I looked at 1st pics again - appears you're running a capacitor?
 

WV Sparky

XS650 Enthusiast
Messages
43
Reaction score
21
Points
8
Location
West Virginia
Left hand side
 

Attachments

  • image.jpg
    image.jpg
    324.1 KB · Views: 12

jpdevol

XS650 Junkie
Top Contributor
XS650.com Supporter
Messages
725
Reaction score
1,463
Points
143
Location
26187
Ok. That's the standard XS Charge w/mechanical advance. It has no known issues with capacitor (the e-advance appears to).
There appears to be a capacitor behind the electrics box and voltage regulator - all presumed ok for now.
I suggest checking timing with strobe light before more carb tuning
 

WV Sparky

XS650 Enthusiast
Messages
43
Reaction score
21
Points
8
Location
West Virginia
Ok. That's the standard XS Charge w/mechanical advance. It has no known issues with capacitor (the e-advance appears to).
There appears to be a capacitor behind the electrics box and voltage regulator - all presumed ok for now.
I suggest checking timing with strobe light before more carb tuning
I appreciate the leads my friend. Added some items to the checklist for me. Thank you I’ll report back
 

jpdevol

XS650 Junkie
Top Contributor
XS650.com Supporter
Messages
725
Reaction score
1,463
Points
143
Location
26187
Yea, sounds like it may even be dropping one cylinder @ idle and just off idle. Still, next step is timing.
 

5twins

XS650 Guru
Top Contributor
Messages
23,283
Reaction score
19,357
Points
813
I think you're going to find the timing pretty close. It wouldn't start so easy and idle nice like it does if the timing was really off. Your off-idle "stumble" appears more like a giant flat spot. That's usually a lean indication. Have you re-jetted, especially the idle circuit (larger pilots)?
 

nj1639

Paleo-simplistic
Top Contributor
Messages
3,805
Reaction score
1,979
Points
163
Location
Switzerland County, Indiana, U.S.A.
I think you're going to find the timing pretty close. It wouldn't start so easy and idle nice like it does if the timing was really off. Your off-idle "stumble" appears more like a giant flat spot. That's usually a lean indication. Have you re-jetted, especially the idle circuit (larger pilots)?
Yeah, post #20 above.
He might need to test different needle positions .......
 

jpdevol

XS650 Junkie
Top Contributor
XS650.com Supporter
Messages
725
Reaction score
1,463
Points
143
Location
26187
Or, passages, or....and the synch is questionable too. I think it's good practice to verify timing before more carb tuning, He has described the rideability as so bad that it won't pull his driveway without revving it up and slipping clutch. Could be too advanced and out of synch. The "tell" for me is that the fuel screws don't seem to produce any changes at all and two sizes on the pilots.

Low exhaust restriction contributes, but can be overcome with tuning. IMO this issue involves more.

It is pretty wild that it fires right up. He also describes first throttle-up decent and subsequent throttle-up stumbly??

Weak or wrong capacitor f'ing the spark? With e-advance that's established, with mechanical??

a step at a time...
 
Last edited:

WV Sparky

XS650 Enthusiast
Messages
43
Reaction score
21
Points
8
Location
West Virginia
The pipes are stock headers with mufflers cut of and some kind of aftermarket tip, zero baffles. Seems the issue at hand could be caused by numerous things? Some more details that I haven’t listed that may or may not be important, sometimes while I’m fiddling with the bike I will get backfires through the left carb or left exhaust. Never the right, as of yet anyway. The bike almost always fires on the first kick. Both plugs are brand new, and the exact plug the bike calls for and they’re NGK’s. As far as the coil, caps and wires I have no idea. The guy before me installed all that. Every time I’ve had the carbs off the bike I spray carb cleaner into the idle passages and every other little nook and cranny I can find and do a bench synch with a sowing needle then adjust the idle back up. I appreciate everyone effort on my issue. Also a little back story, I’m 26 and a 1976 xs650 was my dads first bike which he still has. So this is a big goal for me to get straightened out and rideable. Thanks guys
 
Last edited:
Top