Topic: Hanging idle when hot CB400F

[3pintrace]

Would old o-rings around the main jets cause this condition?  If so, I’ll rip the carbs apart and check.  Was thinking maybe I should just buy all new main jets, needle jets and needles from 4 into 1.  But only if people here think it could help.  Trying not to through money and time away. 

[3pintrace]

Question: I took out one of the main jets and the emulsion tube fell right out when I flipped the carb over.  Should that be press fit in or just dropped in? Thx

[TwoTired]

It's ok for the emuslion tube to drop out.  But, it should have a snug enough fit at the needle valve end to control fuel and air movement through metered orifices rather than past the barrel.

Did you verify the emulsion tube holes were clear?  Did you examine the needle orifice for wear at the end of it?

You HAVE done all the standard 3K tune up items, yes?  I didn't read this whole thread You have checked/replaced the air filter?

Did you verify the air jet and passageways are clear for both the mains emulsion tube and the pilot emulsion tube?

Cheers,

[Deltarider]

Would old o-rings around the main jets cause this condition?  If so, I’ll rip the carbs apart and check.  Was thinking maybe I should just buy all new main jets, needle jets and needles from 4 into 1.  But only if people here think it could help.  Trying not to through money and time away. 

Usually the brassware hardly wears if at all. That's no wonder if you realise how little gasoline passes considering it's a 400cc engine that has no less than 4 carbs. The rubber parts do detoriate over time however and can become brittle. BTW, these are the only carb parts I myself had to renew. If those little O-rings around the main jets do not seal well, the engine will greedily suck in the extra gas that can pass there. It's OK when the emulsion tubes drop down.
As TT mentions, see to it airfilter is OK and air intake is not blocked. A simple cloth left under the body seat can do this.

[3pintrace]

Ok.  So next step is to replace the o-rings on the main jets.  What else should I do while the carbs are out again? 
Was thinking about it again, the idle circuit might be fine.  It is only when I give it a bit of throttle that it will hang.  If I load the engine to bring it back down it will idle ok again.  I thought that would be air leaking in not more fuel but you guys tell me. 
Btw, Air filter is new. 

[3pintrace]

So I’ll wrap this thread up.  Not really 100% sure what did it but 3 good rides without an issue.  Thanks for all the help everyone!

[Alaxy Galaxy]

So I’ll wrap this thread up.  Not really 100% sure what did it but 3 good rides without an issue.  Thanks for all the help everyone!

Dang. And here I was hoping for an Eureka! moment since I have the same issue. Perhaps when I go riding a few times it'll settle itslef also.

[Patrick]

Possibly a sticky slide worked its way loose.

[jakec]

So I’ll wrap this thread up.  Not really 100% sure what did it but 3 good rides without an issue.  Thanks for all the help everyone!

Dang. And here I was hoping for an Eureka! moment since I have the same issue. Perhaps when I go riding a few times it'll settle itslef also.

Alaxy I thought I was having a similar problem about a month ago, but I figured out what was happening, maybe you have the same thing.

Mine seemed like the idle would climb, hang when hot, really, it was only happening when I pulled up to park and had the petcock off, but engine running...  I related the issue to the engine being warm... In reality it was just the petcock being off and the carbs trying to suck some gas.

I went and removed the petcock, and the whole assy., lines, filter, petcock, was all clogged up. I cleaned it all up out and it doesn't happen anymore. So I am thinking that the warm engine had nothing to do with it, just some minor fuel constriction issues that i only noticed when stopped, i.e. after a ride.