aaron7202 wrote:

So I've had this problem for while and now I feel like fixing it. If I go all out on the throttle 1st through second or third, I'll hit a flat spot at 3800-4200 that is really harsh, depending on how warm the car is, it will last 2-10 seconds and then pass, accel kicks back in, reving through to 5500. The RPMs wont pull back or anything, but it just wont go forward - This will not happen in 1st. Only 2nd or 3rd with pedal floored. If I go more smoothly, don't floor it, I don't have this problem. Problem is accentuated with choke on - what would you I change? I am running CD's jetting 32/36 DGV on a basically stock motor with a pertronix and MSD ignitiion. I have a vacume advance dizzy that currently is not hooked up but that doesnt seem to matter cause I've run it both ways. Problem doesnt go away with timing changes from what I can tell. When car is cold, its worse than warm. What good is an 02 if I can't floor it through the gears!! TIA.

Since use of the choke apparently worsens the condition, I would "guess" something is going on with either your secondary or jetting is permitting either too rich or too lean condition at the higher end of your rev range. (The fact that you are tinkering with the timing and not using the vacuum advance makes me also wonder whether you haven't created your own ignition related problem.) I am no expert with weber carbs, but having read the archives, I note the issue has been mentioned before. Suggest you look at the following as a start:

http://www.bmw2002faq.com/component/option,com_forum/Itemid,57/page,viewtopic/t,296747/

http://www.bmw2002faq.com/component/option,com_forum/Itemid,57/page,viewtopic/t,295178/

http://www.bmw2002faq.com/component/option,com_forum/Itemid,57/page,viewtopic/t,292339/

http://www.bmw2002faq.com/component/option,com_forum/Itemid,57/page,viewtopic/t,290341/
(note Berry's comments)


Again, you mention that the choke has an effect on the complained-of condition which strongly suggests fuel delivery related. You did not mention anything about your ignition system and how you might be using:

platinum plugs. or a
50-year old rev-limiting rotor, or an
MSD unit that permits you to dial back the ignition advance, or
resistor plugs with resistor wires with a blue coil and a ballast resistor, or
plugs gapped too small or large, or
a distributor advance that is malfunctioning/sticking/ or badly jury rigged.

If any of the above is true, CD will post one of his now famous diagrams!

HTH

Here is some information regarding a DIFFERENT style Weber carburettor. It is different that "CD-sorry-he-sold-it!'s" patented one-size-seems-to-fit-all-32/36-Webers-formula/pERscription. Pay particular attention to the discussion/advice regarding EMULSION TUBES. Carbs are obviously different, but the theory is UNIVERSAL:

http://members.aol.com/dvandrews/webers.htm

HTH

Aaron -
Please -
attach the vacuum to the vacuum advance

Have the vacuum disconnected during the timing light setting at 1,500 rpm, and the "BALL" mark is aligned in the inspection hole.
Then re-attach the vacuum hose to the distributor.

EVERONE also ASSUMES your distributor MECHANICAL advance is free moving - that the spngs return/retard correctly, and it advances
smoothly with or with out the vacuum pot connected.
Watch your timing light from idle and up to 3000 rpm - the flywheel marks
should NOT jiggle and act irratic - but advance and retard smoothly in the inspection hole.

Now your ready to visit the carb - The ignition timing comes first !!

I also assume your valves are adjusted to 0.007" COLD,
and spark plug gaps at 0.024"

If your float level is not correct - set that next - now to the jets.

Are you sure you have the correct jets in the correct position ie.
Primary side, and Secondary side ?

Float Level 40mm

PRIMARY
idle 60
main 140
air correction 145

SECONDARY
idle 55
main 170
air correction 175

AND -PLUG THE SECONDARY ENRICHMENT HOLE AT THE TOP OF THE CARB AS MY DIAGRAM SHOWS . DON'T ASK WHY- JUST DO IT AND SEE THE HUGE DIFFERANCE IN ACCURATE FUEL METERING THROUGH OUT ALL RPM AND THROTTLE OPENINGS.

_________________
1976 BMW 2002 #2743711(sorry I sold it 12/25/06)
1986 BMW R65 650cc twin 19k miles
1964 BMW R27 250cc single 15K miles
2002 BMW 325xiTouring 29k miles
1984 MERCEDES-BENZ W123 300D Turbodiesel-188k miles fein-DIESEL

Sounds like fuel starvation. Probably Fuel pump

for the thoughts and the library of posts - I'll go through some of the suggestions and let you know...
_________________
Aaron
1972 2002

For anyone that ends up sarching this post I

1) plugged the hole CD was talking about
2) took out a fuel pressure regulator in the fuel line I wasnt sure about
3) Adjusted the float level in the carb
4) Cleaned out the fuel filter

and the problem went away. One of these things solved it. If I had to guess, it was the float level.
_________________
Aaron
1972 2002