weber fine tuning what's wrong?

[ofishel912]

I have touched everything on this engine but still is acting funny. Seems to want to hesitate a bit from take off and sometime sputters. I'm thinking that it's starving for fuel but when I run more rich it still hesitates and idle more rough New rebuild engine, .050 distributor, fuel lines, fuel pump, fuel regulator set to 3 lbs. New webers adjusted to the specs from the CB Performance Manual, also resealed the manifolds to the heads and put new gakets under the carbs to minimize air leaks. Rejetted the idle from .60 to .55 to .50 then back to .55. Main jet from 115 to 120. Idle jets are turned one and a half from bottom ( at this point idles smoothest ) and air by-pass screws are one turn from bottom. Had them at half turn but seems to run a little better at one turn. Venturi 28 mm, main A/C 2.00, F11. Any direction I go with the carbs it gets worse and currently running so so. Also my gas mileage is running less then 20 per gallon. Any thought would be great.

Just a side note, I didn't want to put on a pressure regulator but it did seem to help my gas mileage until it stopped working. I had it set to 2 1/2 lbs and when I disconnected the output to the carbs and turned the ignition to start the electric pump, nothing came out, no gas that is. I then took out the regulator and put the fuel line in a bucket started the ignition and lots of gas a flowing So I took it back and they gave me a new one, two days later the same thing. I put in the third one and checked the output and it seemed to flow fine. Also checked the lines back to the tank and no clogs that I can tell. The fuel filter is about four weeks old and has no sediment in the filter. I'm stumped...

[ron69912t]

If you have 40-IDF Webers and checked the air flow with a Syncrometer you may find the air-bypass screws should be turned all the way in (closed) then all the throats draw the same amount of air.

That's what I found on my recent conversion to Webers. They are great!

If you used flange adapters are you sure the right side carb is not hitting the fan shroud and not sitting flat on the manifold? If so you need to remove the choke lever on that carb for clearance.

The stock fuel pump on my 69 puts out 2-1/2 pounds pressure which is OK for the 40IDF's according to CBP.

Good luck.

Ron D

[ofishel912]

Thanks Ron,

The last time (about a week ago) I had my air screws at bottom, the spark plugs where black and sooty, That is all except one. And the one piston (#3) had the air screw out half turn because when I was syncro the carbs front to back, I needed to increase the #3 to come up with the others. So my thinking at the time was to open all the air screws to half then I tried one turn and that seemed a bit better but not fine tuned at all. Is there another direction to take after I close the air screws to bottom?

[ron69912t]

I would follow the readings of the Syncrometer to balance the front & rear throats equally via the air-bypass adjustments.

Did you disconnect the throttle linkage first and check to see if the butterflys are all completely closed the same?

There is a description on how to adjust Webers on this bulletin board. Do a search for Webers to find it.

Ron

[WFBowen]

In addition to the above, double check your timing & especially verify with a strobe that the dist. is, infact, advancing off of idle. Also, check that your accel. pumps are coming on at the exact moment that the throttles are opening (visually verify without motor running that fuel is delivered at that very moment.) Double check your ignition wires/plugs & valve lash. Is the motor (internal) stock? What Webers do you have & if not purchased new, did anyone "re-work" them? I'm sure that Green912, RonD & others can help you verify your part numbers.
If nothing else works, I'd go back to where you started (i.e. best idle/run). A so-so ignition system will often appear to be a carb/mixture problem (&, unfortunately, visa-versa)
Bill.

[ofishel912]

Stock rebuild with 500 or so miles. The 40 idf webers I bought new. What is valve lash? All wires are new as well as plugs cap and rotor. Also the timing is set to about 6 btdc. I got this by the manual saying that 3 btdc is eqaul to 9/64 inches to the right of tdc. So I doubled it then made a mark, started the car, got the idle to 950 rpm's and timed it to the mark, then I ran it to 3000 rpm's and the timing advanced to 30 degrees or so.

[WFBowen]

Sorry about the terminology, I was referring to valve clerance. Does the engine run well at higher revs/light load, etc.? I know you've checked your float levels, but do you smell gas or does the exhaust at idle seem overly rich (the kind that waters your eyes when you smell it?) Was there a time when the motor, before its rebuild, ran well with these carbs/dist.?

[ron69912t]

Need to correct my previous mail. My stock fuel pump delivers 3-1/4 psi, the Webers need 3 to 3-1/2 psi. Sorry for the mis-information, I just checked my notes.

Here is the Weber how to adjust link:

http://www.kymcovw.com/Pages/tech2.html

Thanks,
Ron