Random loss of power

[MFJustin]

Went out for a ride today and everything was going good until I was almost home and it seemed as though the bike just wanted to die out on me. I would give it a bit of throttle and it would just sputter and then it would kind of pick up for a second and then sputter out again. Once I actually came to a stop it completely died out. I was able to start it again after a few seconds and get it a little further up the road with the same thing happening. Finally I said screw this I dont want to risk damaging anything so I shut it off and started pushing. Several hundred feet up the road I decided to just try kicking it over again and seeing if it was still acting up and vrooooom up and away with no problems whatsoever and was able to get the half mile home. It did this same thing once before a few months back and I was able to get it home. When it happened then I swapped out the plugs because I thought I had fouled them and the problem didnt happen again until now.

A little back story, bike is an '81 with a Pamco ignition kit from Mikes XS with the high output coil, Hughs Handbuilt PMA with Sparx Capacitor, kick start only and no battery. I have upgraded the fuses to blade style so its not using those crappy glass type fuses anymore either. Bike has been running good since I finished the build. A few hundred miles ago I did the usual, cam chain adjustment, valve lash, etc. Recently I have been playing around with carb jets and whatnot but for all intents and purposes I have ridden this bike a lot since I finished the build and the bike has been great, other than me still dialing in my tuning, ive put a decent amount of miles on it and its been fine. Like I said this is only the second time this problem has popped up and after pushing it for a few minutes it fired back up like nothing was wrong. Unfortunately I am very paranoid now about taking any long distance trips over this summer.

Wanted to see if any of you might have an idea of what to take a look at. I thought maybe something was overheating after riding it around for awhile but I've done longer trips before this with no problem other than the one time it happened months ago. My second thought was maybe I was still running rich and fouled a plug but after pulling them they look ok and are actually getting lighter considering I leaned out the jets per 5twins suggestion. The one thing that did strike me odd was that in order to get it started after it was doing the sputtering thing I had to open the throttle about 1/4 turn to get it to fire up. If I left the throttle totally untouched it would just kick and kick and kick with no result. My floats are properly measured but could it be something intermittent with fuel delivery?

Any ideas fellas?

 

[retiredgentleman]

Went out for a ride today and everything was going good until I was almost home and it seemed as though the bike just wanted to die out on me. I would give it a bit of throttle and it would just sputter and then it would kind of pick up for a second and then sputter out again. Once I actually came to a stop it completely died out. I was able to start it again after a few seconds and get it a little further up the road with the same thing happening. Finally I said screw this I dont want to risk damaging anything so I shut it off and started pushing. Several hundred feet up the road I decided to just try kicking it over again and seeing if it was still acting up and vrooooom up and away with no problems whatsoever and was able to get the half mile home. It did this same thing once before a few months back and I was able to get it home. When it happened then I swapped out the plugs because I thought I had fouled them and the problem didnt happen again until now.

A little back story, bike is an '81 with a Pamco ignition kit from Mikes XS with the high output coil, Hughs Handbuilt PMA with Sparx Capacitor, kick start only and no battery. I have upgraded the fuses to blade style so its not using those crappy glass type fuses anymore either. Bike has been running good since I finished the build. A few hundred miles ago I did the usual, cam chain adjustment, valve lash, etc. Recently I have been playing around with carb jets and whatnot but for all intents and purposes I have ridden this bike a lot since I finished the build and the bike has been great, other than me still dialing in my tuning, ive put a decent amount of miles on it and its been fine. Like I said this is only the second time this problem has popped up and after pushing it for a few minutes it fired back up like nothing was wrong. Unfortunately I am very paranoid now about taking any long distance trips over this summer.

Wanted to see if any of you might have an idea of what to take a look at. I thought maybe something was overheating after riding it around for awhile but I've done longer trips before this with no problem other than the one time it happened months ago. My second thought was maybe I was still running rich and fouled a plug but after pulling them they look ok and are actually getting lighter considering I leaned out the jets per 5twins suggestion. The one thing that did strike me odd was that in order to get it started after it was doing the sputtering thing I had to open the throttle about 1/4 turn to get it to fire up. If I left the throttle totally untouched it would just kick and kick and kick with no result. My floats are properly measured but could it be something intermittent with fuel delivery?

Any ideas fellas?

The gas tank has a vent in the gas cap. It could be plugged, which prevents air going into the tank, and fuel starvation is the result. Take the cap apart and clean the small vent hole.