spark but wont hit a lick

[dcycles88]

hello, ive got a good one here . its a 81 xs400 . cdi . i bought the bike not running . it didnt have fire and the carbs were a mess . i fixed some bad wiring that got it sparking again . went through the carbs . when i tried to start it wont hit a lick .the most it will do is backfire sometimes . it has good looking spark on both plugs . i was told the motor was rebuilt and its obvious the head has been replaced . i thought it must be off on the timing . i even went to the trouble to remove top of motor . to my surprise the mechanical timing is dead on . when the left cylinder is in firing position the pulse generator is pointing at the twelve oclock position .is this right ? im thinking maybe its sparking at the wrong time for some reason? i switched the plug wires but it didnt help any . the motor acts like ones ive seen in the past that have jumped timing . maybe someone has a clue about this ? i am at my wits end . thanks

 

[Scorpio1963]

Seems theres been few of us getting at our wits end from our bikes.I think we need to go fishng and step back from them for a day or two.

 

[Bedhead]

I am assuming you are using the electric start? Try kicking it once and see if it hits for you then. I am having some trouble with my 1980 xs400 that I have not pin pointed yet and acts like this on electric start. Almost as if the starter is taking to much power away from ignition.

 

[dcycles88]

Seems theres been few of us getting at our wits end from our bikes.I think we need to go fishng and step back from them for a day or two.

good advise

 

[phate]

Are you sure you are getting fuel to the cylinders? I had the same problem and after about 3 good carb cleanings and switching the wires it runs just fine. I would say use some starter fluid and see if that works. The bikes are known to have problems with not clean carbs so like I said before clean those carbs!

 

[dcycles88]

Are you sure you are getting fuel to the cylinders? I had the same problem and after about 3 good carb cleanings and switching the wires it runs just fine. I would say use some starter fluid and see if that works. The bikes are known to have problems with not clean carbs so like I said before clean those carbs!

starting fluid makes no difference . the carbs are squeaky clean . i even put new jets in . im a decent mechanic but im the first to admit i dont know everything . could the plugs be firing out of the engine but not when installed? it appears to have newer coils with ngk plug wires . this bike doesnt even try to start or even sputter . the only thing its done is backfire a couple of times.

 

[devdg]

try checking your pick up coil and see if it is out of adjustment causing the spark to happen to early. starting fluid would give you a false hit since it can ignite just on the compression alone.

 

[16VGTIDave]

Have you tried swapping the plug wires? It wouldn't be the first time someone had put them on backwards...

 

[Drewcifer]

Pickup coils have a spec resistance that they should show on an ohmeter. I fixed a triumph that had one failing part of the time. It was out of spec.
Give it a look.

 

[dcycles88]

i think i will check out the coils . ive seen one on a car fire but not run before . it was weak . you wouldnt think both are bad but its worth a look . thanks

 

[devdg]

if they show to be in spec check your ignition module and the wires running to it and to the ignition coils, also you can check those to see if they are not weak they have a spec resistance as well.

 

[dcycles88]

i got a lot of checking to do . i got a feeling im going to find some more bad wiring . im not giving up . i will let you guys know when i figure this out .thanks

 

[Bedhead]

Did you try the kick starter? It sounds dumb but mine does it. Electric start= nothing but a loud back fire out exhaust once and a while. Before it gets flooded I get half a kick (on a warm day) with the old trusty leg and its running.

 

[dcycles88]

thats interesting but my kick doesnt seem to be working properly . it only turns the motor over a little bit but its worth a try . thanks