SOHC.co.uk Forums > CB350/400
Bike over heating after 40 mile ride
Skoti:
--- Quote from: K2-K6 on May 02, 2026, 08:42:27 PM ---From this "Just to clarity when the bike died it would not even turn over until it had cooled down" do I understand correctly that it had partially seized, which stopped you turning the engine over ken4004 ?
--- End quote ---
That sets alarm bells ringing especially after a recent engine rebuild.
A partially blocked oil pump strainer gauze screen (possibly with surplus gasket
sealer etc) can cause restricted oil flow to the cylinder head, over heating and eventual camshaft seizure.
I'd pull the sump pan off and inspect the strainer gauze and check the oil filter at the same time.
Good luck
Ken4004:
--- Quote from: Bryanj on May 02, 2026, 11:19:51 PM ---I think you have an electromechanical gremlin that stoped the engine and starter didnt work
--- End quote ---
anything is possible I am not ruling anything out and will continue double checking everything.
I think however that the issue is heat related at its root because it has never happen before in over 200 miles it was a hot day and the hill I went up was quite long and steep so if found out the weakness in the bike.
As I did day earlier once it had cooled down enough I took it easy and made it home without any issues so it’s a bit strange.
Ken4004:
--- Quote from: exvalvesetdabbler on May 02, 2026, 07:08:29 PM ---
--- 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
--- End quote ---
OK you can see why I was looking at the needle heights to make it leaner
Ken4004:
--- Quote from: exvalvesetdabbler on May 02, 2026, 07:40:01 PM ---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
--- End quote ---
Hi Dave when rebuilding the carbs I checked the float heights and they were all spot on, did have an issue with float valves and had fuel leaking out the drains so I have changed all the valves and all looks good .
I have drained the tank a couple of times through the tap and flow was good but will check again .
Can you please clarify what you mean by emulsion tubes ?
I am going on holiday for three weeks on Monday so running out of time but will pick this up again when I get back.
Would you be interested in meeting up when I get back for a coffee at a neutral venue it would be nice to meet you face to face, I am only in Copthorne near Gatwick and I see your only in Wimbledon so not far away from each other.
Cheers Ken
Ken4004:
--- Quote from: Ken4004 on May 03, 2026, 07:10:31 AM ---
--- Quote from: Bryanj on May 02, 2026, 11:19:51 PM ---I think you have an electromechanical gremlin that stoped the engine and starter didnt work
--- End quote ---
anything is possible I am not ruling anything out and will continue double checking everything.
I think however that the issue is heat related at its root because it has never happen before in over 200 miles it was a hot day and the hill I went up was quite long and steep so if found out the weakness in the bike.
As I did day earlier once it had cooled down enough I took it easy and made it home without any issues so it’s a bit strange.
--- End quote ---
When I checked the valve clearances there was plenty of oil around the cam shaft snd the oil light always goes out straight away but I will check the filter and gauze as I said earlier I am not ruling anything out, I don’t really find this frustrating just interesting and will get to the bottom of it.I see this as a learning curve the more I dig into this issue the more I learn so all good experience.
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