xs400 starting problems

David Houston

XS400 Member
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hi guys
i have a 1979 xs400 that i am rebuilding, i have fully serviced the twin carbs (fully cleaned/ new jets and needles fitted) replace both the ignition coils and condensor and points (also checked the camshaft marks to points shaft mark that are spot on) i removed the rocket cover and the points assembly to be 100% sure they were OK.. after these works the bike starts and runs say 6 times, then it wont start . timing is spot on and compression good (120psi each cylinder) when i check the voltage on the ignition coils with ignition switch on it reads 9.8v. is that voltage right if not what could be the problem.
hope you can help, i am loosing the will to live.
cheers dave
 
120 is low compression. 125 is about the minimum for these bikes. New is 155+. Your battery should be at 12.5v+ as well as the coils.
 
hi again
i rechecked the compresion with mates new tester and it is 135psi (dumped my old tester) regards the voltage drop to 9.8v at coil and still showing 12.2v at battery. any idea whats causing the volts drop.
cheers dave.
 
You would need to trace the wires from the battery and see where the drop is occurring. If your bike is all stock you can use the factory wiring diagram to help.
 
Pull plugs and if black or wet then ignition issue.

Timing can be dead on yet if gap is off the bike loads plugs up to quit. Why I experiment with any points to determine a dwell number using an old dwell meter, it is harder than one thinks to set 2 sets the exact same. It made my tuneups much sharper on my CB550.
 
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