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BANGKOK 21 July 2019 13:35
Pepper9187

Help needed :( Cylinder 1 & 2 not firing CB400SF

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Hi there, 


Yesterday i started the bike, all fine, then while it was IDLE 2 cylinders went off (15sec after the start), so the bike is shaking like an old tracor, no power, can't run it.

Checked and pipes for cylinder 1 & 2 are dead cold, i checked / replaced the spark plugs, 1 and 2 were soak, i emptyied all the carbs and they all had gazoline....

 

I first thought that one ignition coil was dead, but after checking the service manual it turns out that tere's 2 ignition coils, 1 for cylinder 1 and 3, the other one for 2 and 4 so it can't be that.

 

What else could it be ? I'm starting to be really worried now, and i'm not a mechanical expert :(((

 

The model is CB400SF vtec 3 (NC39)


Thanks .....

 

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i think about piston ring, how many miles you have on the bike,you live by the ocean?

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best thing to do is a compression test,if you have news spark plug,gas in the cylinder,and good compression,is your ingnition...

 

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Posted (edited)

I live in BKK, the bike has about 40K km, i had the carbs cleaned / sync and valve clearance checked about 3-4 months ago, could they have <deleted> something ? (well i already know the answer).


Would it have taken 4 months before smt went bad if they did something wrong !?

 

Edit : He checked the compression 4 months ago and said it was all good (dont have the numbers, but he was very "happy" about it).

Edit 2 : When you seat on the bike, from left to right, cylinders 1 and 2 are not working, and they're both controlled by a different ignition coil so 😞

 

Edit 3 : Thanks for your messages BTW

Edited by Pepper9187

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Just now, OneMoreFarang said:

You obviously have gasoline. Do you have a spark? Check it with spare spark plugs.

Did the cylinders die exactly at the same time or one after the other? Different symptoms = different problems.

Exact same time, 15sec after start, while it was IDLE, that's why i thought (and really REALLY hope) it's only a small electrical problem.

 

I'll swap the coils tomorrow and check the sparks, too much rain right now & too dark & too sad :(((

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Start with the simple stuff
Spark first before you start tearing anything to bits
Change over components from one circuit to another

Two cyls failing together would indicate a common issue leading to the pair so doubtful it's the cyls or rings

Have you got a multimeter at home......

Sent from my SM-N950F using Tapatalk

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Thanks.

Yah i got a multimeter, what's your plan ?


PS : i rank 1/10 on the McGiver tech scale so i might not be able to do crazy things.

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I have 1 4 - 2 3 for the Honda coil pairs but might be wrong in the notes.

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It's like that :
So 1&4 / 2&3, that's why i doubt it's a coil issue, it doesn't match with my 1&2 not working 😞

 

image.png.c26eebd36f526856b5cf4d4387a5adfc.png

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So it runs ok for 15 seconds and then fails? If so it points to the ecu/cdi.

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12 minutes ago, stubuzz said:

So it runs ok for 15 seconds and then fails? If so it points to the ecu/cdi.

Yap, just like you said. 😞 I'll check all the electronic more in detail tomorrow, i'll post the results here.


For tonight I'm just gona drown my sorrows until i don't ever remember my bike's broken.

 

Thanks everyone *opening the first Leo*

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Posted (edited)

Update :Da-fack, tried to start the bike it's even worst, almost not starting anymore it's really stuck in there.

 

Update 2 : Bad hangover i'll continue tomorrow

Edited by Pepper9187
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When you surface 🙂

 

Is your fuel good? Empty the tank and drain the carbs. Put 1/2 a gallon of fresh fuel in the tank.

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