vokera mynute 14-48 se boiler constant re-ignition

[andyn72]

I have a Vokera mynute 14-48 gas boiler.
A couple of weeks ago, one of the flow valves for the water started leaking.
I drained the system and replaced it with a straight service valve.
The boiler is working ok however, I have noticed it fires up and burns fine for an initial 5-10 minutes.
After this, when the thermostat kicks in, the boiler ignites and burns for 45 seconds, then stops for a minute or so before burning for another 45 seconds, and so on.
Thing is, I cant remember if this is normal but it seems a bit too manic for a normal operation.
Anybody know what the matter could be, have I messed up re-filling it?
Any suggestions most welcome?

 

[andyn72]

Anybody?

 

[nickso]

does it get up to temperature or is it below?

 

[andyn72]

Yes it seems fine.

The radiators are all hot and after a time the thermostat clicks off.
As I said I'm not sure it wasnt always like that, it just seems too quick to go on/off.