happychappy
XS650 Member
Hello, sorry to make my introduction like this. I have been reading this forum since I bought an xs650 from CL a while back. Since I've owned it, it has never run well. It was stored for a while before I bought it. The po said it was running well when he put it up. It was running rough when I went to see it. It ran with a stumble between 1100 and 1700 rpms.
I should also say that this bike is not in riding condition at the moment. I have been slowly working on parts of the bike that need attention as frustrations rise and fall with different aspects of the project. I'll go over what I'm working with so you have a frame of reference (the bike below).
From what I read the stumble I was/am tracking was a pilot jet adjustment that is typical after an intake configuration change. Having gone from the stock air box to the uni I thought this was an obvious culprit and put a lot of time in that. I have taken the carbs off at least 10 times in the last 3 months and tried everything form a 34 to a 50 pilot jet. Yesterday was a breakthrough day. I attached the charger and set it to "start"50 amps and fired it up. To my surprise it ran with no stumble, the best it has ever run. Literally after disconnecting the negative terminal from battery and revving the engine there was the stumble again, connect it again and the stumble is gone. Needless to say I thought this was a good test for the future if I ever have this kind of low rpm stumble since this seems to be a pretty consistent issue with these bikes. I thought I would share the testing procedure and ask you to check the validity of the test. Maybe it will help someone in the future more quickly diagnose a possible issue.
Procedure
1 Turn bike off
2 Connect Charger terminals to battery
3 Set charger to "12 volts"and the "Start"
4 Turn on bike and search for stumble.
5 If there is no stumble remove the negative terminal from the charger and see if your stumble is back. If so you can safely assume the timing chain tension, the valve gap, carb timing, air mixture screws, jets, intake boots and seals are fine and that your issue is somewhere between your rotor/stator (Charging) and the spark plug (Ignition).
Today I am going to try to clean up the charging system make sure its pushing enough juice at idle and test the coils with my multimeter. Having heard what has happen so far any advice you have that could get to me a faster resolution would be gratefully appreciated.
The bike:
1980 XS650 Special bought stock
What I have done
Removed the old wiring harness except for the rotor
Replaced with a harness from TCBros
Removed stock airbox
Added uni pods
Disassembled and cleaned the carbs (looked pretty good for having been stored)
Re jetted pilot to a 47. (seems to be happy there)
Clutch push rod oil seal replacement (leaked oil)
Swapped out the clutch push rod for a single rod (Mikes XS set up)
Timed the cabs with homemade manometer
Replaced battery with one from TC bros.
Replaced the air mixture screws (Old ones were pretty bad and looks like the previous owner had to do a lot of adjusting)
Adjusted the cam chain tension (Was a little loose)
Verified the gap clearances on the intake and exhaust vales.
I sincerely thank you for all the helpful info I have found here.
Thanks
HaPPYCHAPPY
Austin TX
I should also say that this bike is not in riding condition at the moment. I have been slowly working on parts of the bike that need attention as frustrations rise and fall with different aspects of the project. I'll go over what I'm working with so you have a frame of reference (the bike below).
From what I read the stumble I was/am tracking was a pilot jet adjustment that is typical after an intake configuration change. Having gone from the stock air box to the uni I thought this was an obvious culprit and put a lot of time in that. I have taken the carbs off at least 10 times in the last 3 months and tried everything form a 34 to a 50 pilot jet. Yesterday was a breakthrough day. I attached the charger and set it to "start"50 amps and fired it up. To my surprise it ran with no stumble, the best it has ever run. Literally after disconnecting the negative terminal from battery and revving the engine there was the stumble again, connect it again and the stumble is gone. Needless to say I thought this was a good test for the future if I ever have this kind of low rpm stumble since this seems to be a pretty consistent issue with these bikes. I thought I would share the testing procedure and ask you to check the validity of the test. Maybe it will help someone in the future more quickly diagnose a possible issue.
Procedure
1 Turn bike off
2 Connect Charger terminals to battery
3 Set charger to "12 volts"and the "Start"
4 Turn on bike and search for stumble.
5 If there is no stumble remove the negative terminal from the charger and see if your stumble is back. If so you can safely assume the timing chain tension, the valve gap, carb timing, air mixture screws, jets, intake boots and seals are fine and that your issue is somewhere between your rotor/stator (Charging) and the spark plug (Ignition).
Today I am going to try to clean up the charging system make sure its pushing enough juice at idle and test the coils with my multimeter. Having heard what has happen so far any advice you have that could get to me a faster resolution would be gratefully appreciated.
The bike:
1980 XS650 Special bought stock
What I have done
Removed the old wiring harness except for the rotor
Replaced with a harness from TCBros
Removed stock airbox
Added uni pods
Disassembled and cleaned the carbs (looked pretty good for having been stored)
Re jetted pilot to a 47. (seems to be happy there)
Clutch push rod oil seal replacement (leaked oil)
Swapped out the clutch push rod for a single rod (Mikes XS set up)
Timed the cabs with homemade manometer
Replaced battery with one from TC bros.
Replaced the air mixture screws (Old ones were pretty bad and looks like the previous owner had to do a lot of adjusting)
Adjusted the cam chain tension (Was a little loose)
Verified the gap clearances on the intake and exhaust vales.
I sincerely thank you for all the helpful info I have found here.
Thanks
HaPPYCHAPPY
Austin TX