TheSamba.com :: View topic - How possible is itmake a 34 PIC 3 to rich in mixture?

Tue Apr 17, 2012 9:28 am

I know I have been posting a lot. I have used the search function here a ton and am still trying to find the answers.

How hard is it to make a rich mixture on a Bocar 34 PIC 3?

I set the idle with the large screw
then turned the small screw untill the idle reached the highest point.
then backed the small screw out half a turn
then reset idle with large screw.

This is what my haynes Manuel says and now I have a lurch while im under heavy acceleration, like entering the highway.

Some people have said turn the small screw in until the engine bogs and then half a turn out. Others have said 1 &1/2 turns out from where it bogs down.

SO what the true way? Im so paranoid ill make this to rich and ruin my engine

Tue Apr 17, 2012 11:27 am

:idea: Different points of view and experience...heres mine as a VW mechanic of many yrs.

Make sure the screw on the arm just touches the bottom step on the cam with the choke warm and open.

Back off both lge and small screw about three turns and the carb should be hissing real loud.

Turn in the lge screw in until the hissing stops and the idle should be about 900 RPM....at this point the mixture will be rich.

Slowly turn in the small screw until the engine starts to falter and then back off 1-1/2 turns. ( on a 34-3/4 carb) 30pict-1-2 would be 3/4 of a turnl.

Now you can either increase or decrease the idle if needed using the lge screw.

Now you can slowly screw in the small screw again until the engine falters again and then back off 1-1/2 turns.

The procedure may have to be repeated 2-3 times untill trhe engine revs and idles smooth.

Spraying a few shots of carb cleaner into the throat of the carb will also help at the very beginning.

Opinions may vary here but I made my living doing that with no complaints.

Tue Apr 17, 2012 11:31 am

Thank you very much HRVW. That is the most common way to tune the carbs that I have seen but the reason I was questioning my book was the stumble on huge acceleration. Since you made a living on this I guess it works. Lean is better than rich in my opinion. I will tune my carb to this today thank you very much.

Tue Apr 17, 2012 12:14 pm

:idea: Just trying to give some free advice.

Running lean could be a main jet problem. The common jet would be a 116 upt to 127 or 130 with larger cyls.

Try my adjusting method before/after seeing which main jet you have.

Another possibility could be the need for a longer stroke on the pump rod which is adjustable...or the nozzle short on spraying for any exceleration.

Will not argue with any printed man

Tue Apr 17, 2012 2:29 pm

HRVW wrote: :idea: Just trying to give some free advice.

Running lean could be a main jet problem. The common jet would be a 116 upt to 127 or 130 with larger cyls.

Try my adjusting method before/after seeing which main jet you have.

Another possibility could be the need for a longer stroke on the pump rod which is adjustable...or the nozzle short on spraying for any exceleration.

Will not argue with any printed man

So far your adjustment has worked. I havent gotten a chance to run the highway as it was blocked today and had to go on the back roads but the car is actually idling a little bit smoother now. Still wavers a little.

Thank you for the information. Im writing this down in the back of my manual.

Tue Apr 17, 2012 10:03 pm

:idea: Glad to help. Hesitation could be the nozzle not spraying when the carb throttle plate is opening with more air and not enough fuel. Gas should spray right away. Visually look inside the carb (w/o engine running) to see the gas flow from the nozzle. If slow and not a strong spray the need for a New nozzle of diaphragm might be in need...a common thing with the 34-3 carb. The nozzle can be cleaned with carb cleaner and a air compressor. A compressor is always handy in any garage and cheap from Harbor Freight. A 15 gal or higher is the best.

Thu Apr 19, 2012 5:21 am

I think I may have to remove the nozzle. Since I did your tuning the car has worked great! Though suddenly this morning on acceleration in the low gears there is a lurch. It feels like the car is not getting enough fuel and causes a lurch. Once I get into the higher rpms the lurching goes away... Ill pull my air cleaner off tonight and check that nozzle. Where is the diaphragm? I would like to check that too.

Thu Apr 19, 2012 8:05 am

back up , 10feet
and try again.

the motor needs to be good, good compression and no leaking valves
causing induction vacuum to bounce all over the map (all cars, not just VW)
(vacuum gage test) compression gauge tests , discover this fact.

then step 2
the Dizzy must work right. it must match the carb type for vacuum input.
is your DIZZY a 009 or other mixed up parts.?
the advance can be jammed or limited, as can the springs be wrong or missing. or ? use a strobe light and find out if the dizzy is doing its job 1st.

the first step is to make sure you have full advance on the Dizzy.
to the spec. shown in the oldvolkshome page.
http://www.oldvolkshome.com/ignition.htm#A1968M

if not done first, carb tuning is a hopeless task.

Some 009s working right, are late to advance. and causes flat spot off idle
some change the mixtures to compensate for the lacking's of the 009.
eg. running too rich all the time.

been here yet?

http://www.vw-resource.com/mihov_index.html

Thu Apr 19, 2012 8:09 am

see all 4 training films.
the real thing.
a good primer (no pun)

Thu Apr 19, 2012 8:25 am

Quote: Though suddenly this morning on acceleration in the low gears there is a lurch. It feels like the car is not getting enough fuel and causes a lurch. Once I get into the higher rpms the lurching goes away...

we need more info than that. sorry.
we need to know what is not stock on the motor.
spec out the motor. dizzy p/n for one.???

it's bogging, (bogging HOT)
it can bog for lack of advance (spark) or for lack of fuel or too much fuel.
fuel
lean misfire
or too rich misfire. (all cars not just VW)

finding this is hard with out checking everything, (no AFR meter in the shop)
very hard.

but if the spark is good, and timed correct and is advancing like VW built your car at day one, (is it?)
then
it's all in the carb. (or induction air leaks, never tune a carb with leaks)

the carb has many circuits and functions.
the first thing to checks are:
1: is the choke unloaded, that is covered by posters first line, the high speed choke cam. is it unloading to OFF , hot.? OFF is bottom notch.
if not the choke is bad.
2: is float level at spec?. do not skip past this , or you will fail.

3: next, is the HSAP (high speed accelerator pump) that is the thing that
squirts, even key off. HSAP nozzle squirts. the diaphram makes that squirt.

4: is the HSAP activation rod, set to spec for 1cc squirt (read bentleys for yours spec , its there) bigger engines need more... is yours bigger?

5: The HSAP gets rid of TIP-IN BOGS. (spark timing correct)
it enriches the mixture ,just long enough for the carb to catch up to the real venturi air flow. (all carbs and EFI do this effect) (called air slug delay)
(air moves faster than fuel, physics, ask why?)

once the engine uses up the 1cc, it is the idle and main jets to set the proper mixture, the idle jets , work up to 2500 rpm and there is overlap between
the idle and main jets.

rob&dave explain all that. here. www.vw-resource.com

I post all this so you dont chase your tail.
look at the whole system.
not just the carb and win.

Thu Apr 19, 2012 8:31 am

75sb
what is the exact p/n on your SVDA (i could not find it in your vast # of posts)
and who made it. Bosch or Clone or what,?
the back side shows this information. (a mirror works to great effect)
any posts for drive-ablity needs full spec on carb and dizzy.
or all bets off.

Quote: Though suddenly this morning on acceleration in the low gears there is a lurch. It feels like the car is not getting enough fuel and causes a lurch. Once I get into the higher rpms the lurching goes away...

we need more info than that. sorry.
we need to know what is not stock on the motor.
spec out the motor. dizzy p/n for one.???

it's bogging, (bogging HOT)
it can bog for lack of advance (spark) or for lack of fuel or too much fuel.
fuel
lean misfire
or too rich misfire. (all cars not just VW)

finding this is hard with out checking everything, (no AFR meter in the shop)
very hard.

but if the spark is good, and timed correct and is advancing like VW built your car at day one, (is it?)
then
it's all in the carb. (or induction air leaks, never tune a carb with leaks)

the carb has many circuits and functions.
the first thing to checks are:
1: is the choke unloaded, that is covered by posters first line, the high speed choke cam. is it unloading to OFF , hot.? OFF is bottom notch.
if not the choke is bad.
2: is float level at spec?. do not skip past this , or you will fail.

3: next, is the HSAP (high speed accelerator pump) that is the thing that
squirts, even key off. HSAP nozzle squirts. the diaphram makes that squirt.

4: is the HSAP activation rod, set to spec for 1cc squirt (read bentleys for yours spec , its there) bigger engines need more... is yours bigger?

5: The HSAP gets rid of TIP-IN BOGS. (spark timing correct)
it enriches the mixture ,just long enough for the carb to catch up to the real venturi air flow. (all carbs and EFI do this effect) (called air slug delay)
(air moves faster than fuel, physics, ask why?)

once the engine uses up the 1cc, it is the idle and main jets to set the proper mixture, the idle jets , work up to 2500 rpm and there is overlap between
the idle and main jets.

rob&dave explain all that. here. www.vw-resource.com

I post all this so you dont chase your tail.
look at the whole system.
not just the carb and win.

Thu Apr 19, 2012 8:48 am

Motor is 1600 CC DB Carb is Bocar 34 PIC 3 new in August. Dizzy is SVDA from aircooled net the top grade one and Bosch.

Choke is on lowest step when this is happening.

Float level is to spec.

Also has no air leaks as I have spent a great deal of time checking.

accelerator pump (the faucet thing thats squirts fuel down the throat of the carb when throttle is pushed) gives good squirt of fuel.

Timing is set to 30 BDTC without vacuum, with vacuum 40BTDC. Accoridng to Volkshome.com my timing should be set to 25max, yet ive read multipla places that it should be set to 30 BTDC without vacuum which means that when vacuum comes in it advances to 40 BTDC.

Directions on the aircooled SVDA even say 30* without vacuum, 40 with.

Car bogs only on heavy acceleration and in low rpms of motor. I.e. in third anything under 35 it will bog on acceleration.

Directions for tuning were to back both screws on left out 3 turns. Set bypass screw to idle.
Turn Volume screw in untill motor bogs and then back out 1&1/2 turns.
Reset idle with Bypass screw.
Repeat above directions three times.

The bog is very light. I also just put in 93 octane instead of 87 octane to counter act the pinging that could happen from the high timing from the SVDA

Thu Apr 19, 2012 9:23 am

http://www.oldvolkshome.com/ignition.htm#A1968M

this website says im to have 22-25 degrees BTDC is that with the vacuum plugged?

Fri Apr 27, 2012 3:10 pm

So since I have gotten my SVDA timed correctly, I have noticed my fuel economy is down to 22 mpg. I have tested this over three tanks of gas. Before with my 009 and my idle at 1400 rpms I had 27 average. So can I just turn my mixture screw (the small one) in 1/2 to 3/4 of a complete turn? The screw is out 1-1/2 from bogging the engine. All im trying to do it lean out the mixture because I think its to rich.

Fri Apr 27, 2012 7:03 pm

Anyone?

Fri Apr 27, 2012 7:20 pm

zombiebug wrote: So since I have gotten my SVDA timed correctly, I have noticed my fuel economy is down to 22 mpg. I have tested this over three tanks of gas. Before with my 009 and my idle at 1400 rpms I had 27 average. So can I just turn my mixture screw (the small one) in 1/2 to 3/4 of a complete turn? The screw is out 1-1/2 from bogging the engine. All im trying to do it lean out the mixture because I think its to rich.
Look in the bowl of your carb and see if it's too full, or at the line where it should be.

If it's really full, then are you running to rich? Maybe.

Joe

Fri Apr 27, 2012 8:06 pm

I didnt think of checking the bowl. I just thought it was on running mixture. ok ill try that tomorrow thank you.

Sat Apr 28, 2012 9:52 am

zombiebug wrote: I didnt think of checking the bowl. I just thought it was on running mixture. ok ill try that tomorrow thank you.
Just a thought, not sure if it will help. It's worth a try though.

Joe

Mon Apr 30, 2012 9:34 am

Bowl is fine. Im going to pull a spark plug today. I'm just really confused since all I did was switch to an SVDA, time it at 7.5 BTDC idle, 30 BTDC at 3500 rpms no vacuum and re-tuned the carb with the set up HRVW suggested. I'm down to 22 mpg per tank. Before with the 009 I was at 27 average.

What else could be the problem? Should I just keep leaning out the mixture?

Mon Apr 30, 2012 3:51 pm

Did you happen to adjust the screw that rests on the fast idle cam? It should just barely touch the bottom rung when the engine is warm, plus 1/2 turn.

I put a rebuilt 34 PICT 3 on my sedan and was getting 14 mpg before realizing that adjustment was WAY off.