Emissions not failure

[matthew13]

Hi all. 1983 2ltr cu engine petrol van. Took it for an mot today and it failed on emissions. Anyone got any tips to low the emissions?

[davidoft1]

Adjust the mixture

[Rosie n' Jim]

Is it running on standard Solex carbs? What were the immission figures?
 

[matthew13]

Yep I think it's running on its original twin solex carbs. I love in france so the mot might be different than in England but I have a reading of 9.36% CO and it should be less than 4.5%. Also when they do the test they rev the a bit out of it!!
Not sure how to adjust the mixture of if it'll help at high revs?

[lefty67]

Also try changing oil and filters (air + oil) and make sure engine is nice and warm before mot..
See if the garage will ease off on the revs. In uk is says not to rev violently, my mot guy says that's open to interpretation.

[Rosie n' Jim]

I think you're referring to CO2, not CO. 4.5% CO2 is correct spec for the CU engine at idle. They only test at idle over here if memory is correct. Not sure why they rev it so hard. 
Yours is running rich, so either too much fuel or too little air, filter could be restricting flow. Or carbs need setting up. Sarran,  a member on 80-90 club has done videos on this, or for a written guide try this link. https://itinerant-air-cooled.com/viewtopic.php?t=7767
You do not need any special tools, but patience and a methodical approach is a must.

[matthew13]

Just been to my local crazy guy mechanic and he reckons the carbs need regulating but before I should do anything I should change the spark plugs. Does this sound right and if so which ones should I be getting? It's a 1983 2ltr cu engine petrol?

[lefty67]

Here you go
https://brickwerks.co.uk/product/spark-plug-t3-2-0l-cu/