SOHC.co.uk Forums > CB350/400

My CB400 is a cold-blooded little sucker!

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ka-ja:
Drain the carbs for long term storage, whether E5 or E10, ethanol can rot some metals over time.

McCabe-Thiele (Ted):
In modern times we have become accustomed to engines starting straight off the button with fuel injection.
With carbs if an engine is not used regularly they take some cranking over to pull the petrol through to where it's needed.

If you want your 400 to start immediately off the button that can be done - just squirt some easy start into the air intake, it will fire up almost instantly run for 5-10 seconds then splutter a bit as it starts to run on petrol.

Personally I like the idea of the engine cranking over as it pumps oil round the crank & cam before it starts running. I would not advocate the regular use of easy start type sprays.

K2-K6:
Probably a good move to check the carbs for any untoward effects.

The first thing that should happen when cold starting is for the idle jets to go full "suck" against the vacuum created by choking the intake.

Sounds familiar, doesn't it  :) any impairment compromises that effect to take fuel delivery below target, making  it sub optimal. As they say in modern parlance  ;D

The ancient art of stuffing an old rag into the intake was a historic way of "encouraging " the low fuel circuit to get up and go when reluctant. Probably to suck the chunks out of that circuit with any soft debris accumulated :)

Mikep328:
Pulled/disassembled the carbs - all parts/passages as clean as they were when I had cleaned/adjusted them in late '21.  Float levels are not exactly the same as they were then but are all within a mm of their settings.  Bench sync settings are still as they were then so no issues with that.  IOW, I don't see the hard cold start issue I experienced yesterday being related to the carbs. 

FWIW, I started the bike today (fresh E10 yesterday) before removing the carbs and it started immediately with no issue at all.  So it appears to me that the starting difficulty yesterday was the E10 fuel.  As I said, it had been sitting for 4-5 weeks since the last run.  Maybe E10 needs stabilizer added for carbureted engines if it sits for more than couple of weeks!  On my wife's bike and my other bike (both fuel injected),  there is no issue with the same 4-5 week-old E 10.

McCabe-Thiele (Ted):
I use fuel stabiser in E5 in my bikes and our old Merc.

I also add Wynns Dry fuel for the winter into the bike tanks - the Merc has a plastic petrol tank so I dont worry about water pooling in the bottom.

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