Twin Stromberg CD 150's, winter/summer mixture

[daverclasper]

Hi. Since winter to the very hot recent/current weather, I have leaned the mixture off, three times on each carb, totaling about a quarter of a turn on each one.

Car was running ok, though plugs very sooty, except after a long run.

Is this amount of adjustment normal, as I understand they will run richer in the less dense ,hotter weather?.

"Interested", rather than my usual "worried".

Thanks, Dave

 

Edited July 18, 2021 by daverclasper

[Iain T]

Are all the plugs sooty? Is there a difference between the front and back three? 

[daverclasper]

No. Thats what was making think its not the carbs playing up. Same slight turn of mixture screw on each carb, approx 30 degrees, 3 times over 6 months has each time given a good plug colour for a bit.

Not many miles in this period, maybe 700. Air filters are still clean.

Was pinking very slightly this weekend, maybe very hot weather. Not worried about this, or the mixture either. Just interested.

 

[Pete Lewis]

there is no real need to twiddle them if the hot weather has thrown a black plug colour then it was too rich in the first place 

irrespective of the weather 

later carbs had a summer /winter adjustable choke stop that just changed the amount of choke you could pull with the knob

pete

[daverclasper]

Thanks Pete. Will keep as is then.

Never quite got the hang of the lifting pin method, though have read all there is to know I reckon, so have always been going off plug colour.

[Pete Lewis]

plug colour is a good method so long as you are on a decent run and not used choke 

lifting pins    is a light feely lift the pin to feel it touch the air piston then raise the piston about a 1mm /2mm  and note a hint of change in the idle

if it drops 50rpm its lean  if it raises 50rpm its rich  if nothing its about right 

(i use my ears not the pins  anyway)

needs air filters on and youre looking for a hint of change for a few seconds  not a major change ,  its small changes  

big changes means its lifted too far   so quite gentle touchy feely is the key 

removing the filter and lifting with a screwdriver is completely useless the mixture must be set in a road running condition or its a waste of time 

as fitting the filters completely changes the depression and fueling in the carb throat /venturi 

Pete

[dougbgt6]

Just phoned Pete to ask

6 hours ago, Pete Lewis said:

Removing the filter and lifting with a screwdriver is completely useless the mixture must be set in a road running condition or its a waste of time 

Doug: "How do you lift the carb piston without taking the filters off?"

Pete: "You can't on yours, they did away with the lifting pins on late CD150s"  

Doug: But Haynes says that's how to do it! 

Pete: 

db

 

 

[Pete Lewis]

yes the trouble evolved in the 70s when tamperproof carb settings became law to stop us all twiddling the factory settings 

there were all sorts of things like mixture screw covers that destroyed themselves if you dare to meddle if you were caught with a broken tamper proofed carb i guess you ended up in the Tower of London there you just hung around ....till they cut you down 

so all things twiddleable were removed or covered to stop us TWIDDLING 

it wasnt the best idea to come from emission rules of the 70's 

many had a plastic seal with the manufacturers ID impressed in it , repairs had a new number so it was supposed to be traceable

pete

[daverclasper]

10 hours ago, Pete Lewis said:

(i use my ears not the pins  anyway)

 

Is that listening for smoothest running, or other things?. 

[Pete Lewis]

ah wot 

yes  best running . wind jet in to get a mis then back out to make a smooth idle if resetting raises the ide slow it down again 

Pete