Im in need of some help in trying to figure out a boiler problem.
Do the following facts and observations point to anything to anyone here.

- 3 days ago the boiler (an old fashioned gas fired standard boiler -
Stelard Ideal Mexico Super Model CF65 - about 13 years old),
pilot light shut off automatically. I relit it, it stayed on, main burner
came on. Then after 1 hour the pilot again shut off automatically.
I adjusted the pilot screw to increase pilot flame size, and boiler
has worked normally for 3 days.

- 3 days later, pilot shuts off, I relight it, pilot stays on, main burner
comes on, after 1 minute, Main burners AND pilot both go out.
If I relight the pilot, it stays lit. NOTE it only goes out 1 minute
AFTER main burners come on.
Also Note that the main burner flames look fairly weak and the second of
the 2 main burners comes on say 20 seconds after the 1st main burner.

- I now replace the thermocouple. Makes no difference. Anyhow, the pilot still
stays lit as long as main burners dont come on so surely its not the
thermocouple.
The voltage at the gas valve terminals is 240v ALL the time including when
the burners and pilot cut out, so I am assuming there is no problem with
the controller or thermostats. I also assume there is no problem with the gas
valve as the main burners come on for 1 minute.
Note I hear a click from the gas valve when the main burners and pilot shut
off automatically after 60 seconds. (Everything is still cold at this point)

- I now clean out the 2 main burner jets and pin prick flame holes (There is
no dirt I can see)
I DIDNT clean the pilot.

- Still same problem.
- I now notice that when the main burners come on the pilot flame seems to
go out and is therefore not covering the thermocouple tip as it does when
the main burners are NOT on.
- I now adjust the pilot screw again to increase the pilot flame even more.
Now when the main burners come on, I can see a pilot flame which does touch
the thermocouple tip. Also the main burners and pilot now STAY ON.
GREAT - BUT the radiators arent getting hot - only slightly warm, and the
pipes coming out of the boiler that should be hot are only warm, even though
both main burners are now on and running for 30 minutes.
NOTE I can hear and feel that the pump is on and humming.
Also NOTE - the main burner flames still look fairly weak to me but Im not
too sure what they usually look like.

-Bit stumped at this point. Think it could be restricted incoming flue/airways
I blow into the main burners from below.
The second burner actually goes out now, but I can see a small flame at the
bottom of the second burner- below the pin prick flame holes.

-Both main burners are now working again last time I looked - but pipes and rads
are just luke-warm

-Last resort - SOS message on uk-d-i-y

Any ideas greatly appreciated

(The one comforting thought is the weather forecast over the next few days)

SledgeHammerSteve