SOHC.co.uk Forums > CB350/400

400/4 struggles to pick up when warm

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adriangsmith:
Hi All,
Nearly finished finding my way round some of the problems with my 400/4 build.
Just had carbs professionally set up and balanced and the timing set correctly.
However i still have the issue that once the bike has warmed up (10 minutes of good riding) the bike will struggle to pick up from low revs.
open the throttle too fast and it will bog down and die.
needs to be slowly feathered up to around 3000 rpm before it will run smoothly again.
It's fine once going but around town or when stopping it makes it a right pain to ride.

Any ideas where i start looking for the cause of the problem?
something electrical would be my first guess but don't know where to start looking and checking.

Cheers
Adrian

Rob62:
Whenever i read “professionally set up” i suspect it was done by some hairy arsed cowboy...  :o

My advice would be to start with the easy stuff... new plugs first, then look at fuel filters, breathers, fuel flow, air filter, go through all the standard settings, valve clearances, ignition timing, points, condensers, air screws, carb settings etc... test the compression ... Somebody may be able to point to a particular fault they have experienced in the past but if that involves some kind of major strip down or big expense i would still go through the standard settings first... Nowt worst than spending hundreds of pounds and lots of hours only to find you’re no further forward and then later on discover you have a partially blocked fuel pipe or something similar...

hairygit:
Also check that you do NOT have resisted plug caps AND resisted plugs. One or the other is fine, but both together will cause problem like this. Are you running standard airbox?

Sent from my X6pro using Tapatalk

paul G:
I would check the plug colour first as it sounds like it is running weak.
Could try adjusting the air screw a 1/4 turn at a time and having a run.
More than one full turn and the carb settings will need looking at.

Nurse Julie:
+1 with Mr Hairy and Paul. Check plug type and sounds like its running lean to me.

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