Honda-SOHC
SOHC.co.uk Forums => CB350/400 => Topic started by: Athame57 on October 14, 2026, 10:59:06 AM
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My number one and four pistons didn't fire up the other day and given that they are served by the same coil suspicion fell there. I lifted the tank, cleaned a few things up and as I had them handy changed all plugs. All was well again after a brief ride. Today I start up nicely but within about twenty seconds things went bumpy with uneven firing and I was mostly back to two pistons, I'm not going anywhere except a workshop like that.
I'm not sure it is the coil though, I expect electrical things to fail in a complete way from the start.
This started one day after a lout on an e-bike pushed me over on the move but I don't really see a connection.
Your thoughts?
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Most likely it's not the coil itself but the HT leads, these are affected by moisture & movement.
HT Leads are part of the coil unit on these bikes, it could potentially be the plug caps, might be worth shortening the leads slightly if problem is near the caps.
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Check the points.
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Check the points.
I have electric ignition ;)
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Check the points.
I have electric ignition ;)
😄 OK, check the wiring connections all the way from side cover to coils. Could have been bumped in your "off".
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Whatmake of electronic?
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Do you know how old your coils are?
When my 500 had a misfire that varied between one cylinder and sometimes two inspection of the HT leads showed obvious signs of age related deterioration especially near where they exit the coil.
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Whatmake of electronic?
I honestly don't know anymore. I got them from DSS years ago and they have been very good.
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Do you know how old your coils are?
When my 500 had a misfire that varied between one cylinder and sometimes two inspection of the HT leads showed obvious signs of age related deterioration especially near where the exit the coil.
Probably about five years old.
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Sounds daft, have you checked in the dark for signs of HT sparking where it should not.
After the incident with the e-bike there are a few areas that might come into play.
As has been mentioned, check for loose connections, cracked plug caps or crack in a coil casing.
If it was the right side that hit the floor, any damage to the points cover, potential damage to electronic circuit board. Could you revert to points in the short term to eliminate the electronic ignition
Could petrol sloshing in the petrol tank have dislodged enough grime to block the carbs?
Is the kill switch damaged, worth checking wires in the headlamp, ignition switch area.
I would be thinking the accident has messed something up.
Last thing are the new plugs beyond suspicion?
Hope you can sort it.
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Reason i asked is that on the us site there have been reports of someDyna units failing, and thats the originals not the knock offs.
You say the coils are 5 years old again genuine or pattern, either way have you checked the resistances against the manual, in all hoesty i dont think ive ever seen a failed coil, leads yes and from Honda that means a new coil but not the actual coil
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I lifted the tank, cleaned a few things up and as I had them handy changed all plugs. All was well again after a brief ride. Today I start up nicely but within about twenty seconds things went bumpy with uneven firing and I was mostly back to two pistons
What did the spark plugs look like? Since replacing them corrected the issue for a short while, perhaps they were fouled by carbon or excess fuel.
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What did the spark plugs look like? Since replacing them corrected the issue for a short while, perhaps they were fouled by carbon or excess fuel.
Very sooty :(
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Sooty means you have a carburetor problem: too much fuel or too little air. It takes a spark to light the fire to make soot. It ran for a while with the new plugs until they also fouled. Be aware that once fouled, the plugs will stay fouled even after the cause has been corrected. To clean fouled plugs, I burn the black off with a propane torch.