Author Topic: CB400F No spark, possible faulty kill switch (Read 7064 times)

Jore · « **on:** January 27, 2013, 02:04:47 pm »

Last night I took a ride about an hour long, 45 minutes in to it the bike while I was in a red light. Moved it to the side of the road, hit the starter and it didn't turn, felt like It had low voltage (my battery is kind of in it's last leg), tried to kick it and it fired in the first go.

After that I parked it outside a party, left it about 2 hours there went outside to show it some friends fired back up using the e-start, but it felt kind of slow to start.

Anyway my kill switch has been having some issues, but if you don't touch it it's not a problem. Last night it got fondled up by someone and later by me trying to start the bike. I tried cranking it so much that the battery went flat, tried kicking it and nothing, tried a running start and nothing.

The battery was so dead we even tried to jumpstart it with another bike, it did get some juice but still the bike wouldn't start.

I left the bike there, took out the battery came back home charged it all night, headed back to the bike and nothing, it's cranking like usual, gas tank's full, but no spark, took out one of the leads to see if there was a spark and nothing.

So my best guess is that the kill switch crapped out last night. Is there a way to bypass it? Just to see if it's that or if it's something else, later today i'll be heading back to bike, but armed also with a pickup truck just in case it's a no go.

steam-powered man · « **Reply #1 on:** January 27, 2013, 02:41:27 pm »

i have checked the wiring diagram for a cb400f, and the kill switch makes/breaks the black to black/white wires. it seems to me that if you find the bundle of wires inside the headlight bucket that comes from the right-hand control, and jump the black to black/white wires the switch would be jumped out.

but don't do anything unless you get confirmation from someone else here on the board, pls! i don't want to be responsible for some poof/smoke in the bucket. just wanted to offer some advice on where to begin. good luck!

Jore · « **Reply #2 on:** January 27, 2013, 02:58:42 pm »

Thanks! I've looked up the diagram and it also seems to be the white/black and black wires that I need to connect together in order to bypass the thing.

736cc · « **Reply #3 on:** January 27, 2013, 04:55:50 pm »

Squirt some WD40 into the rh switch housing. Also, what did you do to your bike recently? Wash it? Open hl shell? Change points? Those might be a clue to the gremlin.

MoMo · « **Reply #4 on:** January 27, 2013, 05:25:24 pm »

The connection for the black and b/w is in the bundle on the left side of the frame under the tank. 12v on black and then 12v at b/w when switch is in the run position...Larry

Jore · « **Reply #5 on:** January 27, 2013, 06:19:24 pm »

Thanks I'll try both things.

As to what has been done recently, i've only changed the spark plugs to a set of D8EA from NGK and the spark plug boots to 5K ones also from NGK.

But nights here are really hazey/misty so after a few hours outside the bike was wet from that.

camelman · « **Reply #6 on:** January 27, 2013, 09:41:31 pm »

If I were you, I'd open the switch up to get a better look at it. There is a plastic piece in there that fails with age and can break into pieces that can stop the e-start from working. There are also some soldered connections in there that can fail, which will not allow the coils to get power. If the plastic piece is broken, then just buy a new switch. Trying to source a used switch off eBay, etc, will result in you buying an old switch that is either already broken or ready to break soon. If it is just a failed solder connection, then it is easy to fix.

Of course, you might just have a loose wire elsewhere, which would be even easier to fix. I recommend checking the fuse box too. The fuse holders can loosen or corrode, which may result in the symptoms you are experiencing.

Camelman

Jore · « **Reply #7 on:** January 27, 2013, 10:20:16 pm »

dumb question, but where's the fuse holder in these bikes? I have been pocking around it but I don't recall seeing it.

MoMo · « **Reply #8 on:** January 28, 2013, 12:56:56 am »

Quote from: Jore on January 27, 2013, 10:20:16 pm

dumb question, but where's the fuse holder in these bikes? I have been pocking around it but I don't recall seeing it.

under the side cover, there is a black box on which the cap comes of and the fuses are under...Larry

Jore · « **Reply #9 on:** January 28, 2013, 07:32:43 am »

Thanks Larry

malcolmgb · « **Reply #10 on:** January 28, 2013, 08:15:48 am »

Concentrate on your battery problem first, the description you gave points toward that. The chances are you flooded the engine with the failed starts earlier, they will struggle to run on a flat battery, I think anything less than about 3,000 RPM is a drain on an already flat battery.

Jore · « **Reply #11 on:** January 28, 2013, 09:33:01 am »

The battery has been on the charger for some time now. But i'll buy a new one ASAP, I thought also about the flooding, but last time I tried to start it with another battery it didn't have spark.

Jore · « **Reply #12 on:** January 28, 2013, 04:55:48 pm »

We'll I recovered the bike

I went directly and bypassed the kill switch, and that gave me spark, as mentioned earlier the bike was flooded, but after a few tries it started with a bang (it backfired), but it started let go of the throttle and the bike died. Started it back again, held the gas, and moved the idle screw so it would idle at around 3K as to avoid drainage from the battery. Will idling the bike would climb a bit on the rpms and then go back down to 3K, variation was about 300 rpm. Rode it back home, but it felt low on the power.

About 3 blocks away from my place the bike stalled tried giving more gas but it still died. Tried to restart it both with the electric and the kick start, but nothing. Currently the bike's in my garage.

One more thing, and I think this is important. The bike has no fuse block, I know that some models only had 1 fuse, but since mine's an american model I thought it had 3.

camelman · « **Reply #13 on:** January 28, 2013, 06:49:19 pm »

Hmm, heavily retarded ignition will cause bangs and definitely a loss of power. You might as well do a 3000 mile tune up and check all the usual suspects. Then, chase down any electrical gremlins.

Jore · « **Reply #14 on:** January 28, 2013, 07:04:27 pm »

I had a tune up done by the honda shop a few weeks back. But when they did it the bike was running with the wrong plugs and messed up caps, so maybe the ignition got retard then.

I'm never going back to the dealership BTW.

Over on the DTT forum they've suggested that I may have charging issues, so coupled with a less than perfect battery it may also cause issues.

My battery is back on the charger, and tomorrow i'll be getting a voltmeter to test the system and the battery.

camelman · « **Reply #15 on:** January 28, 2013, 10:03:06 pm »

There are a lot of things it could be. Charging system and regular maintenance is a great place to start. The right side handlebar switch can be suspect though. If the points plate was not tightened after adjustment, then it could have slipped too... which would retard the ignition.

Let us know what you find.

Camelman

w1sa · « **Reply #16 on:** January 28, 2013, 10:19:11 pm »

It may have become so low on spark (battery/charging/kill switch/ slow running/etc) that the plugs may have sooted up......to a point where, you should at least check/clean and preferably replace them....will make further run testing more valid.

Jore · « **Reply #17 on:** January 28, 2013, 10:26:58 pm »

Well, there's several issues to address this week on the bike, but also on my job, any ways my attack is something like this:

-Rebuild the kill switch (if it's dead permanently bypass it, till i can change it).
-Address a fuel leak.
-Find where are the fuses on the bike.
-Check the charging system.
-Check the timing.

On a side note, my fuel petcock has 2 outlets, one of it goes to the carbs, and the other one's blocked by a piece of hose and a bolt, is there a better way to block it?

Edit: My plugs are new (less then a week old) So I didn´t think of that, thanks for the heads up.

Viktor.J · « **Reply #18 on:** January 28, 2013, 11:02:24 pm »

I dont know the similarities to a cb750 switch, but when I found this thread I kind of #$%* my pants.... Looks scary

http://forums.sohc4.net/index.php?topic=80532.0

Jore · « **Reply #19 on:** January 28, 2013, 11:16:45 pm »

Thanks, that's very helpful, on my bike at least the switch is a lot simpler, it only has the kill switch and the starter button. So I hope it will be less of a hassle.

Viktor.J · « **Reply #20 on:** January 28, 2013, 11:55:46 pm »

NP, that's great man !
Keep us updated on the progress at least have a similar problem.

Jore · « **Reply #21 on:** January 29, 2013, 04:16:16 pm »

Another quick question:

Do spark plugs foul even if the bike was running?

Frostyboy · « **Reply #22 on:** January 29, 2013, 05:05:02 pm »

http://www.davidsilverspares.com/CB400F-SUPER-SPORT-1976-USA/part_162766/

jude0007 · « **Reply #23 on:** July 29, 2013, 06:42:54 am »

Hi, it's been awhile since anyone has posted on this. Did you ever figure anything out? I am having the same issue on a bike that is new to me. Ran well for 2 weeks, then would not start. No spark on any plugs. First thing I wanted to check was possible issues with kill switch. I jumpered the black, black-white wires at the kill switch side. I assume that is correct? Anything else I should look into?

Jore · « **Reply #24 on:** July 31, 2013, 06:20:23 pm »

I took the switch apart and rebuilt it, to ensure contact I put some solder on the contact tabs so it would be higher, i also pulled the spring a little.

But yeah, what you did with the wires is basically the same I did.

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Author Topic: CB400F No spark, possible faulty kill switch (Read 7064 times)