JRM83
XS400 Member
I was having a frustrating problem that i finally solved, so i thought anyone with a similar issue could benfit from my experience. The bike is a 81 xs400 with digital ignition. (Not the points iginition).
So since last winter, when my bike was left outside and uncovered, i was having the problem where, on the highway, it would run great up to 5500 rpm where it would start to stutter . it would barely get to 6000 rpm and then there was no power left. So i started with the usual stuff, plugs and wires. No change. The plugs were whiteish. ( my timing is a bit advanced, but i only run on 91 octane) so i went upsizing the jets, both pilot and main, to two sizes over stock. No change. So checked the valve lash . One was quite off, from when i dropped an exhaust rocker arm, but after fixing it there was still no change. She would still only rev to 6k.
Next i got a spare spark plug. Disconnected the plug cap on one side, stuck in the spare plug and grounded it . After running the engine both sides were getting nice blue sparks right till redline BUT when running on left side only, she would rev till 6k, then die, or stutter, or go wonky. So i switched the plugs, wires and coils from left to right. But the problem stuck to the left side. So i cleaned all the connections in the harness . No change. Things were getting frustrating. Now my bike has the digital ignition with the pickup and not the points ignition. So i adjusted the timing all over the place but no change. I pulled the pickup off looked at it ( you cant really take it apart or anything ) and reinstalled it , and now my bike wouldnt start at all. Sigh. So after fiddling with it for days, i finally got it at least running ( the rotor was off 90 degrees when reintalled , idiot) i was now frustrated and out of ideas. Any idea what i missed. My only options left were that the pickup was gone, the cdi box was gone, or some wire somewhere was shot. I was really hoping it wasnt the last one. So i pulled the cdi box, under the battery, cracked it open. It looked perfect, brand new inside. But i got out the soldering iron, and freshened up all the soldering spots on the circuit board. Reinstalled it . And low and behold. She ran . All the way up to redline. I just got back from a two hour ride and she is running like a champ.
Anyways, sorry for being so verbose, but maybe this will help somone in the future with this frustrating problem. Cheers.
So since last winter, when my bike was left outside and uncovered, i was having the problem where, on the highway, it would run great up to 5500 rpm where it would start to stutter . it would barely get to 6000 rpm and then there was no power left. So i started with the usual stuff, plugs and wires. No change. The plugs were whiteish. ( my timing is a bit advanced, but i only run on 91 octane) so i went upsizing the jets, both pilot and main, to two sizes over stock. No change. So checked the valve lash . One was quite off, from when i dropped an exhaust rocker arm, but after fixing it there was still no change. She would still only rev to 6k.
Next i got a spare spark plug. Disconnected the plug cap on one side, stuck in the spare plug and grounded it . After running the engine both sides were getting nice blue sparks right till redline BUT when running on left side only, she would rev till 6k, then die, or stutter, or go wonky. So i switched the plugs, wires and coils from left to right. But the problem stuck to the left side. So i cleaned all the connections in the harness . No change. Things were getting frustrating. Now my bike has the digital ignition with the pickup and not the points ignition. So i adjusted the timing all over the place but no change. I pulled the pickup off looked at it ( you cant really take it apart or anything ) and reinstalled it , and now my bike wouldnt start at all. Sigh. So after fiddling with it for days, i finally got it at least running ( the rotor was off 90 degrees when reintalled , idiot) i was now frustrated and out of ideas. Any idea what i missed. My only options left were that the pickup was gone, the cdi box was gone, or some wire somewhere was shot. I was really hoping it wasnt the last one. So i pulled the cdi box, under the battery, cracked it open. It looked perfect, brand new inside. But i got out the soldering iron, and freshened up all the soldering spots on the circuit board. Reinstalled it . And low and behold. She ran . All the way up to redline. I just got back from a two hour ride and she is running like a champ.
Anyways, sorry for being so verbose, but maybe this will help somone in the future with this frustrating problem. Cheers.
