SOHC.co.uk Forums > CB500/550

Starting from cold issues

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paulbaker1954:
My 500 four K0 starts on second kick in summer but does still need choke.

I don’t really use the bike in the winter but went to the other day and getting it going was an ordeal after it had stood not run in a cold and damp garage for around a month.

I have tried the priming trick, various combinations of throttle position etc but it’s just a pain to start.

Once going and not even fully warm starts on the button.

Carbs are fully rebuilt Gerben units, no air leaks, float levels all bang on.

Fitted with Boyer ign and micro coils.

I have just ordered some new plug caps in case some damp etc is affecting them.

I have tried altering the pilot air screws 1/4 turn either way but no luck.

Is this hard starting just down to not being started for a while and is this usual ?

Bryanj:
Yes and yes plus the boyer, like most electronics, needs a top notch battery to fire

Erny:
Paul, interestingly I have the very same issues as you on my CB550K1

I would say starting with kick is practically impossible on cold engine in colder weather and pretty difficult on warm engine (using choke usually helps). This is with current carbs 069A (40/100 jets)

Interestingly, previous carbs set I had 022A (38/100 jets) were better for warm kick start (started on 2nd kick, w/o choke), I never tried them with kick when cold so cannot judge.

Col start on 069A requires using choke much longer at the beginning compare to 022A before in order to keep engine running on all 4 (of course I still need to keep some trottle to prevent engine stop until is warm enough)

I have boyer ign too with stock coils. And both carb sets were rebuilt by Gerben. All brass genuine Keihin

Erny:

--- Quote from: Bryanj on December 12, 2020, 09:36:19 AM ---Yes and yes plus the boyer, like most electronics, needs a top notch battery to fire

--- End quote ---
In my case low battery is out of question, always fully charged before cold start

K2-K6:
You've ordinarily got most conditions (as stated) going against you to initially fire petrol into combustion.

Full choke and "priming" may not help in this instance. With the plug and whole combustion chamber metals cold,  along with ingesting damp cool air,  then the mix is difficult to propagate a flame front fully so it snuffs itself rather than advances.  As soon as you get even a modicum of heating and normalising combustion conditions the problem will reduce.

You could try initially cranking it with no choke and listen for any firing,  then without stopping turning it over, start to bring the choke in slowly to see if that catches it.
This is just trying not to overwhelm the air with too heavy a fuel load initially so that the cold mixture is moved more toward "dryness" to favour getting it to light up. A bit like holding a newspaper across an old fire place to get it to draw  :)

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