CB400T cab question for the FOAK

A few months ago I bought a 1977 CB400T that hadn't been run for some
years.. I've fitted new tyres, chain and sprockets, air filter, oil and
filter and things like exhuast seals. I cleaned the carbs (float bowls and
jets) and looked at 1 of the diaphragms - the other is harder to get at. It
ran well on the bench - I had a bit of choke on. Today I rode it properly
for the first time (20miles to the MOT station). It accelerated through the
gears and cruised normally, but when I slowed and dropped a gear it
hesitated (for 1 to 2 seconds) when I opened the throttle to accelerate
again. It felt like fuel starvation. If I opened the throttle very gradually
it picked up (gradually) without the hesitiation. It's a bit lumpy on
tickover unless I pull the choke out a little bit.

The MOT man says it won't be a problem for the MOT. But when I get it back I
want to sort the problem out. What do the FOAK suggest might be the problem?

John

 

The smaller jets or fuel passages may still be partially blocked. Take off
the carbs and _completely_ dismantle them. Remove any rubber/plastic parts
and soak the whole carb bodies in clean brake fluid (or as some here
maintain, cheap fizzy cola).
Leave for a few days then clean in dishwasher and blow out all
jets/airways/passages with compressed air.

JB

 

The carbs weren't cleaned out properly the first time, or more shit has
got into them.

 

Possibly down to one of the slides sticking slightly.

 

Doubt it, but something occurs to me - CB400T carbs don't have bloody
diaphragms, do they?

Eatmorepies, you're a fuckwit ;-) Or you've got *very* non-standard
carbs on your bike.

The key to me is the choke helping: pilot jets, methinks, but
certainly, somewher.....

.... <pauses for effect>

.... <fx: drum roll>

.... shit in the carbs.

 

Doubt it, but something occurs to me - CB400T carbs don't have bloody
diaphragms, do they?

Eatmorepies, you're a fuckwit ;-) Or you've got *very* non-standard
carbs on your bike.

1. apologies to TOG for incorrect reply - evidence of fuckwittery.

2. What I replied ....

Whilst I confess to the possession of boundless supplies of fuckwittery I
did find a rubber membrane about 3cm across under a cover on the side of the
carbs - I took this to be a diaphragm.

The nice MOT man has just rung to tell me the bike's ok and I'm going to
take the carbs over to a friend who has an ultrasonic cleaning thingy - a
reasonably large one with proper cleaning stuff in it. I suppose I'll have
to remove the rubber things and anything else non-metallic that I find.

John

 

Probably a good idea.

The Dreams and Super Dreams used CV carbs, but with steel pistons
instead of rubber diaphragms. Honda used the same carb design on a
great many bikes, including the CB500T (spit!), the DOHC 750cc and
900cc fours, and the CBX six. Seemed to work OK on all of 'em. Don't
know if any other manufacturer used steel piston CV carbs.

 

Are the carb pistons steel? I thought they were Aluminium.

 

Are, yes, I think you're right. Mea culpa.

<Waves hands vaguely> Metal, not rubber, anyway.

 

If you need any spares, I have 3 sets of carbs in various states of
dismantlement.

Paul.