[Chasfield]

Like others I have found that the cold start enrichment device on the 28mm Micarb of my classic 500 is best left for very cold days. For regular cold starts choking the toolbox air intake hose with an improvised loose fitting bung works better (an aerosol paint can top did it for me). Sufficient air leaks past this and via the toolbox lid for effective but not too drastic choking.

Obviously this is not a ride away solution but it helps for the first stage of warm up with the machine on its center stand.

[clamp]

Interesting--- A cold start device  is for cold starting the engine. Restricting air flow to enduce a richer mixture so as to enable cold combustion is what the cold start device is for, but does it in a engine friendly way.

    Purposely restricting air to the carb as in 'choking' literally sucks raw fuel from the jet needle.

     

[Chasfield]

I take your point but it is worth noting that many cold start devices on carburetor fed motorcycle engines are a quite crude in their effect, e.g. supplementary slides or butterfly valves, not to mention 'tickler' buttons that introduce raw petrol into the induction tract.

My external choking approach gives me docile first firing with a cold engine and I remove the choke within a few seconds. The built in cold start lever, on the other hand, seems much more drastic in effect - the engine shows no signs of life whatsoever when it is engaged and so far I have restricted its use to priming strokes on the kick-start. Maybe it will come into its own on a frosty morning in December.

[clamp]

A tickler dislodges the float from its seat, simulating a malfunction of the float and seat mechanism there by flooding the float chamber allowing fuel up into the venturi.

     If your engine shoes no sign of life with  the stock cold start engaged then It would be logical to assume that it is not working. Why you think that it would therefore work in colder climes is confusing.

[Chasfield]

I am assuming that it is grossly over enriching the mixture for a cold start at  at 20 centigrade. At 0 centigrade it may just work great.

As you say, it may just be broken.

[clamp]

Engage the cold start device whilst the engine is warm and running,--you will soon know if it is working or not.

     A condition of "too rich' for a cold start?

       A ticker would be such a device if such a condition was possible.

[Chasfield]

Tried that just the other day. The engine continues to run, but roughly, if the enrichment device is engaged after it has been started.

[clamp]

Then it would seem likely that the enrichment device is working but not to full capacity.

   I would firstly remove the plunger, clean and blow out the galleries feeding it, other than that my thoughts drift towards a low fuel bowl level.

    Is the rubber grommet on the plunger damaged or split?

[Chasfield]

It has seen better days - looks a bit perished.

[clamp]

Suppose you could put some heavy grease around it,--- see if it was that.

[Chasfield]

Might get a look at it over the weekend. Thanks for the advice.