Carbproblems with 34PICT

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DizzyFeeling
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Carbproblems with 34PICT

Post by DizzyFeeling » Mon Jul 01, 2013 4:00 pm

Hi everyone!

I´m having trouble setting idle to my newly restored 1600 engine, also the carb has been restored by ultrasound-cleaning and a fresh rebuild-kit. I have checked for leaks around carb and intake/ manifold but not found any.

Baseline:
Mixturescrew turned out 2,5 turns from bottomed out
Air bypasscrew turned out 4 turns from bottomed out
Throttelarm stopscrew adjusted to just touch the chokes fast idle cam and then 1/4 turn extra
Ignition set right, valves set right

Electromagnetic shutoffvalve has not been changed since it seems to work, there´s an audible click when ignintion is turned on and when tapping the 12 volt-wire to it, it gives off a strong click-but could it still be an issue??

When starting engine it comes to life without hesitation, runs at about 1500rpms with choke engaged and slowly slowing it´s revs as it starts to warm up. If I tap the accelerator at this point it immedeately slows down and stalls. It starts again fairly easy and will stay running if I keep revs around and above 1500, the engine is crisp and there is no hesitation when accelerating but it cannot idle, it immedeately stalls.

Any input is welcome, thanx ahead people!

Tom

Clonebug
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Re: Carbproblems with 34PICT

Post by Clonebug » Tue Jul 02, 2013 8:22 am

Which jets do you have in it??

Idle?
Main?
Air Correction??

Also make sure you have a way to measure the jets as what they say are not always what they actually are, even if new.

Start with a 55 idle and 130-140 main. Air correction should be a 75z or 80z.

My guess is you need to adjust the volume control screw.......turn it in or out to get it to idle. Once you have it idling you can adjust for best lean idle. Make sure the engine is nice and warm when trying to adjust the carb. You want it idling pretty low when you do the best lean idle so get it down to 850 rpm or real close when doing Best lean idle.......

Standard procedure is to have the valves adjusted on a cold engine and the points, plugs and wires in tiptop shape with advance in the 7.5-12 degrees at idle depending on which distributor you are using.

Oh..... and if your throttle shaft is worn you will have a hard time getting it adjusted due to the vacuum leak froom that point.
Stripped66 wrote:The point wasn't to argue air temps with the current world record holder, but to dispel the claim that the K03 is wrapped up at 150 HP. It's not.

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Marc
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Re: Carbproblems with 34PICT

Post by Marc » Tue Jul 02, 2013 10:48 am

What distributor do you have, and how is the initial timing set?

In my experience it's usually faster to start out richer and work your way towards lean. I start with the "volume" (small) screw backed out 4½ turns from shut.

DizzyFeeling
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Re: Carbproblems with 34PICT

Post by DizzyFeeling » Tue Jul 02, 2013 12:47 pm

The carb is the one that came with the engine, it has 130 mains, 55 idle, but not sure of air correction, will check later.
I already checked for leaks and can´t find any, all that seems in good order.

Valves were adjusted on reassembly of the engine and I checked them yesterday evening again to be 100% sure, and they´re still good.

Timing is set at 7.5 BTDC with a Bosch vacuum advance dizzy JFU4 113 905 205, new points, new wires.

There has been no way of trying to adjust idle, since there just ain´t no idle! when the engine is moderately heated up, the little "idle" there is, falls off and engine stalls unless I hold the throttlearm open 1/4 full

I will try with opening up the volumescrew another 2 turns and see where it goes, I´ll keep you posted.

Thanks
Tom

DizzyFeeling
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Re: Carbproblems with 34PICT

Post by DizzyFeeling » Tue Jul 02, 2013 4:09 pm

Hello again!

Well, here´s what I´ve got so far-engines finally idling! Yeay!!

I turned the volumescrew out to 4.5 turns but still no idle, it ran a little while longer before stalling, but marginal.

Tried again and with finger on throttlearm to keep it running, I heard loud hissing from the carb and that got me thinking, is it supposed to sound like that? could not remember hearing that before on a running engine. I then started slowly turning air correction screw inward hearing hissing sound falling away until I finally could let go of throttel and the engine ran at idle all by itself.

I turned volumescrew in until engine started running slower, backed screw out slightly and then stopped to check where screws where at.

I have to do this correctly tomorrow but right now it looks like this:

Volumescrew 3.5 turns out from bottoming out
Air correctionscrew 1 turn out from bottoming out

For now I´m satisfied and will promtly treat myself to a beer and tilt it in your direction gentlemen, thanks for your input it´s greatly appreciated as always!!

Tom

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Marc
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Re: Carbproblems with 34PICT

Post by Marc » Tue Jul 02, 2013 7:42 pm

DizzyFeeling wrote:...Timing is set at 7.5 BTDC with a Bosch vacuum advance dizzy JFU4 113 905 205, new points, new wires...
Pretty much meaningless to me. xxx 905 205 is a VW P/N for a distributor all right, and JFU4 is a Bosch designation.
There's no 10-digit Bosch number, such as 0 231 137 035 or something similar?
If not, can you post a photo of it?

A DP1600 should have either a DVDA (vacuum canister with two nipples, proper timing 5°ATDC) or SVDA (both vacuum and centrifugal advance mechanisms, 7.5°BTDC is correct). NO vacuum-only distributor is correct with a 34PICT-3 carburetor, the ported vacuum signal is far too great and it'll have full advance at idle.

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Re: Carbproblems with 34PICT

Post by helowrench » Tue Jul 02, 2013 8:27 pm

Since it is a carb, there is not a set # of turns that we can give you.
Each engine is different,
Does anyone have the link to setting a 34-3 ?

I usually start from where it idles on its own, then touch the small screw, turn it in or out until the highest idle is achieved. (Slowly, using 1/4 turn increments. And every third adjustment, blip the throttle to clear the engine)
use the big screw to keep the idle below 1000 rpm.

Once the highest idle is achieved, turn the small screw rich (out) 1/4 turn.

That is off of memory, I hope someone posts a link

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Marc
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Re: Carbproblems with 34PICT

Post by Marc » Wed Jul 03, 2013 4:49 pm

helowrench wrote:...Once the highest idle is achieved, turn the small screw rich (out) 1/4 turn.
That is off of memory, I hope someone posts a link
That's about right, when everything's in good stock condition. Usually a little on the fat side, where driveability's good - say ~3% CO. If you need to pass an emissions test (typically they want <1.5% or even less) it'll take about ¼ to ½ turn IN from best warm idle - any further and the HC starts to climb from lean misfires.
30 years later, with a worn-out carb, incorrect air cleaner/distributor/etc., all bets are off - but that's how it went down in the `80s
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I started looking on the 'net for a good link and the first one I came across (at a site which many consider to be a reliable source) maintained that the volume control screw richened the mixture when turned in...don't believe all you read.
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