I have had this for quite a while. I start her up and she pops like a regular knock. Not too loud just regular. I run her for five minutes and it clears and runs like a dream. bit of lag but nothing that worrys me. I was thinking timing - not sure? 1600.34 pic, 009 dizzy.
Maybe piston slap (faint clanking) when cold, my 1500 Beetle used to be a little noisy for the first couple of minutes. Tony
blocked heat risers....pre heat air cleaner solenoid not working/properly....tin ware/thermostat missing/ maladjusted? Sounds like it's just taking a little longer to warm up (atomize fuel) than prescribed another suggestion: slight intake/exhaust leak that seals when engine warms and expands
[quote="vanorak, post: 534720, member: 1397"..pre heat air cleaner solenoid not working/properly.... Sounds like it's just taking a little longer to warm up (atomize fuel) than prescribed[/quote] Sounds plausible, the bit about the pre heat solenoid. defo not burning all fuel initially. how do you check pre heat solenoid, would /should this affect choke?
http://www.vw-resource.com/air_cleaner.html#vacuum the procedure should be in bentley...I'll check my factory manual but it's in German so takes me a while to figure it out
Self explanatory really, but: When the engine is cold. vacuum draws on the thermostatic valve (top) which is open, allowing vacuum to draw on the Flap valve...so hot air from the hose is dawn into the air cleaner from around the exhaust/cylinder tin..so better fuel atomization As the air in the cleaner warms up, it closes the Thermo valve which shuts off the Flap valve allowing cooler air to be drawn into the cleaner via the snout....this should happen gradually, according to engine and ambient air temp...clever Guys those VW engineers....and then we go and stick £10 pancake filters on em'
Definitely not a knock. I have heard this sound too. And benefited from the increased fuel economy of following Malc when it's been running rich
The other part of the set up is the heat riser that transfer hot exhaust gas thru the manifold and out to the silencer,,,when these get bunged up (which they do) less heat is available to the manifold... I reckon this is why folk have issues with Weber progressives...not because of the carb itself, but due to the lack of pre heat....they then spend ages rejetting, and over compensate, when maybe modifying the stock airbox and re routing one of the heat risers back to the silencer (instead of just back to another exhaust) would sort it out....Not my thinking...VW and Bob Hoover
