SOHC.co.uk Forums > CB350/400
Bike over heating after 40 mile ride
Ken4004:
Here is a picture of one of the spark plugs I took after I got home from my ride when it over heated, it looks normal to me but you might not agree .
Light tan colour which according to the manual is the normal colour , all spark plugs look the same.
Ken4004:
I did have a look at the breather hole in the fuel cap but couldn’t see a way of taking it apart easily.
Rain stopped play this afternoon but managed to get the carbs back to standard settings , c it checked the valve clearances which all look good, reset the points gap so will if I get time tomorrow recheck the timing snd rebalance the carbs.
If I get time I’ll take off the silencer and give it a tap with a rubber mallet and see if any more rust comes out.
I don’t think you can remove the baffles out of this Silencer as it appears to be welded together unless anyone knows different.
exvalvesetdabbler:
--- Quote from: Ken4004 on May 02, 2026, 06:47:10 PM ---Here is a picture of one of the spark plugs I took after I got home from my ride when it over heated, it looks normal to me but you might not agree .
Light tan colour which according to the manual is the normal colour , all spark plugs look the same.
--- End quote ---
I would call that black/sottey
Skoti:
--- Quote from: exvalvesetdabbler on May 02, 2026, 01:46:08 PM ---I had similar issues with the wear in the emulsion tubes giving blackish plugs, confirmed it by swapping in a spare set followed by a new OEM set. The bike would stumble on off on the throttle at low revs in traffic , made it a bit of a handful. My son behind me on the road said it stunk of petrol.
There was corrosion pitting around the top of a couple of tubes. I could easily see the difference by dropping a needle in and seeing how much it wiggled.
No other changes were made other than swapping out the tubes and needles followed by a static balance.
All caused by leaving the bike for a couple of years with fuel residues in the carbs.
The D8EA was the replacement when the ESL was discontinued.
Regards
Dave
--- End quote ---
Been there and seen that, good post and good advice.
Absolutely agree...
exvalvesetdabbler:
I don't think fuel flow is the issue here, you're getting more than enough.
Time to check the easy bits before tearing stuff apart too much
Spare bit of pipe on the fuel tap into a clean recepticals and try the fuel tap in both pisitions
Choke flaps fully open once the leaver is clicked in the open position
Corrosion inside the post where the main jet sits, or fuel getting by the o ring
Float heights are the float valves sealing or allowing the fuel level to rise too much
Clean plugs with a blow torch before trying again. There's always a risk that you have cleared the problem but not burned the crud off the plugs during normal running.
Sounds like you are going through the same mill I did 15 years ago. I replaced all the brass ware in the rebuild kit but the needles and emulsion tubes are not in the kit.
Regards
Dave
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