Cb400n no start problem

S

sully1987

New Member
Hey everyone,

I've recently required a 1980 CB400N that was a guys half finished problem, purchased with the assumption that it wasn't starting and may have an issue with the CDI unit.

So I've been tinkering around and since putting a battery into the system, and most of the lights and indicators are working, however when trying to start the bike, there is the starter solenoid click and nothing more.

I've tested the solenoid, the starter motor and both are working fine individually, also I have tested the voltage through the system reaching the starter motor and I am expecting the engine to at least turn over but still nothing.

I'm curious as to whether I need to have the CDI and ignition coil in perfect working order as well before this will happen, or whether the engine should be cranking without it.

Also I have bypassed the solenoid and also tried to start the bike going straight to the starter.

I don't think the engine is seized as I can spin the drive shaft when the bike is in neutral (no chain installed at this stage)

Wondering whether this is an easily diagnosed problem or whether I have a lot of work ahead of me, or whether I have unrealistic expectations of what should be happening

Thanks




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Possible that it's seized.

I would get the chain on and roll it to be sure. A glance down a plug hole with a flash light might help, too.
 
Should it roll in gear still? I was hoping it was just electrical and not mechanical haha he had replaced the Pistons so I was hoping it would be free.

Thanks for your help I have seen you're quite the expert on all things electrical so was hoping you'd reply


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If it's in gear it should still roll, but it will be difficult to push. Higher gear will make the rolling easier.
 
The studs on the solenoid; use a multimeter measure the resistance between them while pressing the starter button.
This will tell you if the solenoid is any good. Hearing it click is a good sign though.
 
So update, had a look at the starter motor's internals and something had fried between the bolt for the positive feed and the coils. Fixed that and now it spins but when connected to the bike only half cranks like the rod is seized or something. I can hand turn it with a spanner on the stator casing but there is resistance, is this normal? Will it only crank properly if all electronics are connected, I.e CDI and ignition coils to fire the Pistons so they will spin?


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remove your plugs, and then try to turn the engine over.
It should spin quite easily, much easier than with the plugs in.
There should be almost no resistance (apart from valve train) so you should be able to push it around easily.
I don't think the coils and CDI are in circuit with the starter motor so it should still spin a good amount of oumpf.
 
What could be the issue if there is resistance? I can imagine a plethora of things


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sully1987 said:
What could be the issue if there is resistance? I can imagine a plethora of things


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Click to expand...

For the solenoid? Any number of things. Cheap part though. Just easier to replace than to worry about what went wrong.
 
Sonreir said:
For the solenoid? Any number of things. Cheap part though. Just easier to replace than to worry about what went wrong.
Click to expand...

Not the solenoid but the stator and whatever the starter motor has to turn to work


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Yeah... any number of things...

Valve train, timing chain, starter clutch, etc.

First step is to pull the spark plugs. Engine should be fairly easy to turn at that point. Just a few ft/lbs should do it.

If it's still difficult or something is binding, it's time to start taking things apart.
 
don't be, i have a 78 cb400t, you can take the top end apart in 45 minutes if everything plays nice.
then it's easy enough to see if it was the top end or bottom end.
 
farmer92 said:
remove your plugs, and then try to turn the engine over.
It should spin quite easily, much easier than with the plugs in.
There should be almost no resistance (apart from valve train) so you should be able to push it around easily.
I don't think the coils and CDI are in circuit with the starter motor so it should still spin a good amount of oumpf.
Click to expand...

Tried doing this it spins over easier but still not quick and efficiently enough to start I don't think.....


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