Author Topic: B31 - won't idle when cold  (Read 149 times)

0 Members and 1 Guest are viewing this topic.

chrisb

  • Blue Star
  • **
  • Posts: 59
    • View Profile
B31 - won't idle when cold
« on: 11 June, 2022, 20:11:19 »
Finally getting to grips with my B31.  Can now get it to start first time (mostly), and it runs nicely, but it is reluctant to idle when cold (not matter what I do with the advance/retard or air valve).  When it is warm it idles ok.  Where should I start with investigations / fixing?  I know the timing is spot on (checked many times) and it has new fuel lines, fuel tap and tank cleaned.  Many thanks

B Murphy

  • Royal Star
  • ***
  • Posts: 215
    • View Profile
Re: B31 - won't idle when cold
« Reply #1 on: 11 June, 2022, 21:02:30 »
You're not on your own, mine is exactly the same.....I think they are all the same. When I start mine from cold I just hold the engine speed above tick-over and within say 80 seconds when the barrel warms up I can hear a definite pick-up on the revs, I can then let go of the throttle and it would tick-over all day long very nicely.

DAVE BRADY

  • Golden Flash
  • *****
  • Posts: 1982
    • View Profile
Re: B31 - won't idle when cold
« Reply #2 on: 12 June, 2022, 07:33:28 »
Hi,

Most bikes will not idle when cold unless there is something to hold the throttle open a bit other than a person.  If you have a choke fitted then you may find that the bike will idle on choke and as the engine warms you can ease the choke off.
I use the 'hold the throttle open for a while' method.
After idling for a while check the colour of the plugs to ensure the idling mixture is correct.

Dave.
« Last Edit: 12 June, 2022, 08:19:27 by DAVE BRADY »

Mike40M

  • Royal Star
  • ***
  • Posts: 105
    • View Profile
Re: B31 - won't idle when cold
« Reply #3 on: 12 June, 2022, 07:56:11 »
Only one of my eleven bikes idles cold. A fuel injected Ninja. Have a couple of bikes with extended AMAL throttle stop screws that makes it easy to adjust idle speed.

idie

  • Golden Flash
  • *****
  • Posts: 771
    • View Profile
Re: B31 - won't idle when cold
« Reply #4 on: 12 June, 2022, 09:43:42 »
My B33 and M33 certainly will not idle from cold. I start the bikes and ride off, once some heat gets into the cast iron of the barrel and head it will idle, usually within a couple of hundred yards.

chrisb

  • Blue Star
  • **
  • Posts: 59
    • View Profile
Re: B31 - won't idle when cold
« Reply #5 on: 12 June, 2022, 10:43:21 »
Hi Guys, many thanks for the advice.  Relieved to hear I don't need to start chasing down problems with the idle!