Yellow flame and excessive smoke

[blackhill10]

I have just done a full service on a 422 with new burn mat (McMaster Carr material) and a full cleaning. Cycles through just fine and stays burning but the flame is only blue on initial ignition before changing to yellow and the exhaust is smoky.
looking back at previous posts I have forced in more air and removed the air damper ( no change).
is it likely I did a poor job with the mat? Should I have glued the whole thing down and not just 3 dabs as the manual suggests?

[dfitz3390]

is your solenoid damper working ? are you sure the air intake system and exhaust are clear ? is this the reason you rebuilt the unit or is this a new problem . when you took the unit apart did you make sure the heat exchanger was clean ? also you should not pressurize the intake on this it could cause more harm than good. why someone would suggest it is beyond me. are you sure you didnt miss any gaskets ? when you mention full service can you give details ?

[blackhill10]

is your solenoid damper working ? are you sure the air intake system and exhaust are clear ? is this the reason you rebuilt the unit or is this a new problem . when you took the unit apart did you make sure the heat exchanger was clean ? also you should not pressurize the intake on this it could cause more harm than good. why someone would suggest it is beyond me. are you sure you didnt miss any gaskets ? when you mention full service can you give details ?

Intake and exhaust are clear plus I had them apart to clean fully.
unit kept shutting down and long overdue for maintenance which was reason for full service. There was a hefty carbon build up inside although flame sensor was clean and well positioned. Igniter is in good shape. I did see carbon build up under and up to fuel nozzle which I suspect was shutdown problem.
i replaced burn mat, burn ring was not warped so re-installed it
i cleaned out the heat exchanger (not at all bad) and replaced all gaskets with new . I am currently bench testing it before reinstalling.
How do I test the solenoid damper? Is that a likely candidate rather than the burn mat? I read that the mat can give problems if not dead flat, is that true?
Thanks!

[blackhill10]

is your solenoid damper working ? are you sure the air intake system and exhaust are clear ? is this the reason you rebuilt the unit or is this a new problem . when you took the unit apart did you make sure the heat exchanger was clean ? also you should not pressurize the intake on this it could cause more harm than good. why someone would suggest it is beyond me. are you sure you didnt miss any gaskets ? when you mention full service can you give details ?

Second response:
Okay, I found the damper solenoid and it is working properly.

[dfitz3390]

in order to verify the mat didnt lift you may have to partially disassemble .
how much air did you put to it ?

[dfitz3390]

is this what your manual says ? On the Monitor 422
A. Apply glue<P No8217) on the burner bottom
as shown in Figure5-1.
B.
Figure 5-1
Put the burner cloth on the burner bottom,
afterwards press and straighten out the
burner cloth so that it is glued flat and even
on the burner bottom.

[blackhill10]

Thanks for all the info and sorry for the delay in responding. My computer crashed.
the mat had lifted as you suggested, plus the damper o ring had split when I took a close look at it.
All is good now.