[mr average]

Hi, I have a 2 litre engine fitted into my 72 bay and it will not stop popping on the 3rd and 4th cylinder side. I have checked for leaks, changed plugs, leads, checked timing several times, new cap, rotor arm and have even fitted petronix but it still pops! While being new to all this and learning fast I still can't seem to stop it from popping.
A more mechanically minded friend came over and suggested the carb be next on the list to check, a couple of years ago the carbs were set up by someone using a rolling road.
My friend wasn't to sure about how to check/clean/adjust the carbs (twin 40 dells). For a start one has a small u shaped pipe which blocks off 2 ports and the other one doesn't. Could a carb problem be causing the popping, could the idle jet be partly blocked, the float level too high or could it be running to rich/lean? Could it need balancing?
Are there any good threads, websites or books on checking/setting these carbs?
Thanks for any help

 

[Jay19_55]

try taking out the idle jets and blowing air throught them popping on dells is usually down to a bloked idle jet!

take the air fillter off the top of the carb and you will see four brass bits sticking out the top take out the two smaller one (idle jet holders) and blow throught them

The dell superperformance hand book is a great book for these carbs!

Jay

 

[mr average]

Thanks for your reply Jay
When you say 4 brass bits sticking up, do you mean 2 on each carb and is it a case of just unscrewing them to take them out?
My carbs have 2 brass bits on each carb.
Thanks

 

[mr average]

Does anyone know where I can get a copy of the dellorto super performance hand book from?
Thanks

 

[pete nice]

Try Eurocarb in Reading.

Check your idle jets are .55 sized too. They are the smaller ones next to the large twin brass pipes poking up. You should be able to see them if you have an inspection hatch.

 

[blackbug72]

If the popping is coming up through the carb for 3&4 cylinder, it's usually because it's running too lean, e.g. blocked carb idle circuit, blocked idle jets, airleaks from carb base gasket or manifold gasket, damaged/badly adjusted mixture screws etc. Is the carb popping at all revs or just when the idle circuit is operating ? If the popping is through the exhaust, then it's almost certainly a leak in the exhaust system i.e. manifold leak, cracked header, poor header joints, knackered muffler etc. CB Superformance book will really help fault finding. Looking down on either carb with the air filter removed, you should be able to see the main jet stacks (2 per carb, tall brass columns screwed into top of carb) and the idle jet holders (2 per carb, v short brass 'plugs' recessed into the top of the carb next to each main jet stack) - unscrew the idle jets and blow through to clear any blockages, before you think about a full carb stripdown. Also, make sure that the mixture screws are set right i.e. does popping stop when the mixtures screws are turned further out on that carb

 

[Jay19_55]

As Spaarky says!!!!

PS ,spaarky turned out my idle cicuit was blocked up with crap! a freind soaked it in stonger stuff than me then poked about with some wire!! there running fine now! gonna take it down to a rolling road next week some time ! cheers for the help! JAY

 

[blackbug72]

Crackin result Jay - glad you got it sorted, now time to break it using the loud pedal