Centre Mount 40idf woes

[jamesbissland]

Hi All

I have just bought a Beetle with a 1641 and it doesn't seem to be running as good as it should

When it sits idling at traffic lights it gases out cars all around and exhaust starts burbling sometimes (it actually sounds pretty awesome tbh!) and has terrible fuel economy

Its a 1641cc
Running 042 40x35.5 heads
Engle W110
German 009
Centre mount 40idf with 28m Venturi

I have pulled the jets and have found

Mains 145
Emulsions F11
Air Correctors 155
Idle 55 (Cylinder 3&4) & 50 (Cylinder 1&2)

Is it common to have different idle jets ??? Im guessing someone has done this to compensate for the minor difference in runner length?

I am in New Zealand, right on sea level, and ambient temperatures range from 25F (mid winter) to 85F (mid summer) so nothing extreme

Would anyone have recommendations on changes to the about carb configuration?

I have read somewhere also about drilling a 2mm hole in each butterfly when running a single IDF.. is this still recommended??

Lastly, I have notice that it has 195/60R15 tyres, so when cruising around town it is sitting on the 2000rpm mark, which from what I understand is right on the circuit change over mark? Would this effect fuel economy? My gut feeling is yes, because currently it is terrible

Many thanks in advance!
James

[ainokea]

Does the carburetor have the recommended 2mm holes drilled in the throttle plates? I would think not and the idle jets should be the same. you might be setting the idle speed exposing the progression holes in the carburetor body. The 2mm holes might help from exposing the progression holes and help with a rich idle. Also check your float level should be about 30mm drop and 10.5mm without compressing the spring

[PEPPE]

little CC, big valve, 110 cam , 009 does not help a lot for good running in economy. would be better to use dual carb in an engine like that. i would check also the compression of the engine, those heads have usually big chambers

[Ol'fogasaurus]

Not all 009s are the same, some are good and the others are a mixed bag. The 009s are out of a bus and the timing starts to advance at somewhere around 26° First you need to have the distributor spun to check bushing and to see where and if the advance is working. There is a stamped version and a cast version with, as I remember, the cast version being a better choice. A lot of guys use the 010 but don't use the vacuum side of the advance.

Also check the cap and rotor as they can be a hidden fault. This summer my stepson's 1835 started dropping in power so the first thing I suggested was to do a capacitance check on the plug wires. They all pegged the meter but when he checked the high tension wire from the coil to the cap it didn't peg out but did go part way. He didn't notice it but I did and had him recheck it. We pulled a high tension wire off his other rail and it didn't even move the needle; the high tension wire was"dead". He got a new one and got his power back.

A lot of things to look at isn't there.

Removed the jabber and completed the sentence.

Lee

[rs58rag]

55 idles, 190 main air . Don't drill throttle plates, there's an air bypass on carb if needed.

[ps2375]

Are heat risers connected? They are very important for a carb that far from the heads.

[jamesbissland]

yip, heat risers are connected and working well

[ainokea]

Try this test, blip the throttle, if there is a hint of a bog on acceleration, your vents are to big, which I doubt is your case. If however, the idle speed takes a few seconds to return to idle, your vents are to small. I would guess 30mm vents would be better for your 1641cc.