Need Advice - Carb Popping

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Need Advice - Carb Popping

Post by dcd » Wed Jun 07, 2017 4:12 pm

Hello there,

My type 4 engine suddenly started loud popping from both Carburettor's at 3000rpm and above.

Engine is stable at idle, no shaking no popping no back fire no misfire.

CO level 3.5% at idle and 5 to 6 % at 3000 rpm

Stock 2.0 engine, dual weber 44idf on a 1978 westfalia.

i checked and double checked :

- Spark plugs , wires
- re adjusted Timing (replaced distributor, coil, condensor ....)
- Fuel lines and fuel pressure (3 psi)
- removed and re installed Exhaust (if blocked)
- Checked Valve Clearance
- Carbs Jetting
- did a compressions test
- Checked any vacuum leaks
- empty fuel tank - change of fuel
- changed fuel filters.

any ideas ? i ran out of them

Please check you tube link :

Thank you

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Location: Brisbane Australia

Re: Need Advice - Carb Popping

Post by wreck » Wed Jun 07, 2017 4:59 pm

Check the rotor and cap , the rotor has a resistor in it that can burn out , did you check the plug leads with a multimeter for resistance ?, did you time it by any chance with the vacuum lines connected ? very hard to diagnose anything over the internet .
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Re: Need Advice - Carb Popping

Post by Piledriver » Thu Jun 08, 2017 1:58 am

The fact that it idles fine kinda sidesteps the typical reason ~any car with IDFs has popping issues...
The carbs design funnels any crud that gets by the craptacular leaky gauze air filters straight to the idle fuel jets or into the float bowl.

The "Jet Doctor" air correction hole snorkels supposedly eliminate the direct into the jet crud issue, (as well as reduce the chances of "drowning" in heavy rain) but proper dry synthetic air cleaners for Webers exist now, the off road guys swear by them. ... ange_high=

Its worth pulling the idle fuels and blowing them out, and reset best lean idle.
You may have adjusted around some crud, but are lean at cruise/light throttle.
That's what causes the popping.
I, for one, regularly embrace our new robot overlords, as I am the guy fixing the robots...

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