To Whom it may concern.

I am looking for help/professional opinions. I have a 1970 beetle, which i have had for quite a few years. Like most beetles, i guess it has been on and off the road too many times to count. Everything in the engine bay is practically new. Yet the one thing we have had the most dramas with,, is the CARBURETTOR .

Constant problems with getting this beetle running great, (it has run good) are slowly breaking this enthusiast’s love for the car. We have Had constant problems with this carb, everything else seems to be fine. It starts first turn.

It idles well but hesitates/flat spot on acceleration with popping and slight backfires.

Check video VIDEO-----

I have tuned the carb to these specifications .....
http://www.vw-resource.com/34pict3.html 
http://www.vw-resource.com/30PICT2.html 

2.1/2turns out on volume screw and adjust idle.
The valves were set before that at .004 clearance, the timing i think is good.

Specifications.

Solex H30/31PICT carby./ The tubes facing outwards had rubber covers on them, so these were sealed, not sure what they are for. Believe the side one is for vacuum advance.

PICTURE HERE

The carb was bought new but have had heaps issues with it, possible lemon. We had to replace the float with second-hand float, also the fuel inlet tube to bowl, BLEW out mid travel. That has been glued back in. Also the choke works with butterfly opening as it warms, but the stepped cam does not step down with it. The Shut off solenoid works fine.

Thought it may be getting too much air, sprayed WD-40 around bay to no avail.

New parts include...

New Flamethrower Coil
New Flamethrower Distributor
Fuel filter fitted
Fresh Oil
New Leads
New Fuel Pump
New Alternator
New accelerator cable
Valve cover gaskets
New Manifold & Carb gasket
New Battery
New Exhaust +++ few more things

My conclusion is that i bought a LEMON carb, and that maybe if i bought a new one. It may fix these issues. My main concern is i buy a new carb of the same type, and result in the same issues. Or it is not the carb at all and something else.

I have done mostly all the work myself and enjoy learning more, but am a little stuck for advice on this one.
Any advice/opinions would be GREATLY appreciated.
I thank you for taking the time to read this.
Regards Jason.

http://s910.photobucket.com/user/jjwebb123/media/BeetleRunning_xvid.mp4.html 

Running Engine Today, Its a bit hard to hear, but you can hear slight Popping and backfiring on revs.
Like a flat spot or hesitation.

Got me stuffed as ti what is cuasing it.

Side of Carb

Engine Bay

Front carb. The front pipes poking out, i am not sure what they were intended for. They were covered in a rubber boot like cover when new.Which over time became britle & fell apart. So they were sealed off as they were.

Have you inscreased the stroke of your fuel pump to squirt more fuel in on throttle opening (ie acceleration?)
Can you confirm the accel pump is working (see fuel squirt down the throat of carb if you pump the throttle)?

What size idle & main jet you are running? Maybe swap em' for original (remember to swap emulsion tube as well for matching main/emulsion)

Is the distributor advance working? (Can check with strobe, or by rotating rotor and checking it returns). Try setting it to at least about 10 deg BTDC STATIC in any case.

The procedure for setting idle mixture and speed in Bentley manual seems the clearest. Does the carb respond to adjustemts of the two idle mixture & speed screws on its side?

I'm not a professional mechanic so if I'm off target ignore me, but I cannot see any vacuum advance on the distributor or vacuum pipes anywhere.
All the best. Rob.

The rotor springing back is the 'quick' test that advance mech is OK.

Is it a twin-port 1600? Or a 1300, or some other/non-original engine (can tell from letters at start of engine no.) Can tell if it's twin-port by looking at where manifolds bolt on to heads.
Is there a vacuum connexion on the left hand side of the manifold, about 1 or 2 inch below the carby?

The choke shouldn't be needed in hot climate, so you could deactivate it (as per Muir), and use a cable tie or some wire to hold the fast idle cam out of the way until you work out the other issues.

Most the jets and some other parts could be interchangeable between the 34 PICT and the 30/31. The Main & Idle certainly should. The Idle should be on the RHS, brass - just screws out with ordinary screwdriver. The Main is on LHS. Remove brass plug with 13mm spanner, and jet is inside carb on far side. Can be removed and replaced without removing or dismantling carb. If it is blocked, blow it out (and that fixes the problem!). Both jets have the sizes engraved in the top. Idle should be ~65 (or maybe slightly smaller). Main should probably be 112.5, or bigger... not sure, our experience is mostly with the later 34 PICT's. Anyway it depends on the individual engine, not what a book says.

As Joel says, the valves should be set to around 0.006", esp. for exhausts. But it is most important that all INtakes are all the same, and all EXhausts the same. e.g. You could leave all the In's at 0.004", and set all the Ex's to 0.008" , and the engine should run just as smooth.
Joel said the fuel stream should hit the butterfly, but I thought it was supposed to squirt down without hitting anything (so as to get to chamber as fast as possible)?

Also have you checked condition of spark plugs, and put in correct type? (If you're removing them, it's usually best to put new ones in.)

The "throttle valve adjustment", the screw that hits the fast idle cam, should never be used to adjust idle speed (I think one of your 'net references said to). It is adjusted to just sit against the bottom of the fast idle, and then turned in ~1/4 turn. The idle speed is then adjusted only with the large screw on LHS of carb.

Alot to take in there. Might take me a few attempts to answer all questions.

*It is a 1500Single port, no vaccum connection on manifold
*The Rotor is springing back

Spark plugs could be due for replacement,i did pull them out and give them a good cleaning.

I understand the choke may not be needed in these hot climates, but ever since adjusting valves and choke, it is starting the best it ever has.
Beforehand the valves were all over the place,after adjusting to .004 it seems alot better,im not saying they are perfect but defidently a difference.
I always thought they changed to .006 at 71 and 70 are .004, im not sure, seems everyone has different opinions.

Looking from top of carb, brass tube jet on the right has 50 engraved in it,
Looking through 13mm hole on LHS, Bit hard to see, looks like its says 120

I adjust idle using large bypass screw on LHS. once fast idle screw is adjusted its not touch again.

I also asked ROB from VW Resources, he also leant towards Jet size and Timming. I bought a timming light today(not sure how to use it yet)
But might have a play around.

Backfiring, popping etc. is usually caused by running too lean, running too-retarded timing (or advance mech. not working), vacuum leaks around manifold/intake area, or exhaust leaks allowing air into the exhaust system. (Running too rich doesn't cause obvious running problems. But possibly unburnt fuel could pop inside hot muffler.)

Jet No's seem about right... Now that you've removed the brass plug, it should be possible to REMOVE the Main jet (long normal-type & size screwdriver:- the end should slightly "engage" in the jet's slot) and see if it's blocked. If it has a "tiny looking" hole in it, it's gummed and is causing very lean running off-idle. (Blow the gum out.) If you're not game to remove jet with the carb installed, you can remove carb., or remove the top cover.

Is the coil connected the right way? i.e. (-) to the points, (+) towards the ign. switch.

Is it a normal "Flat-Spot/ hesitation" problem on acceleration, or a real "I don't want to go much faster than idle" problem?

The questions may be a pain in the bum, but there should be enough clues otherwise in your answers/info. for the real forum experts to diagnose problems if none of these basic ideas help.

I recently replaced a 30PICT2 with a H30/31 on a 1500SP in my '70 Beetle.
The H30/31 came stock with 120mains, 50 idle, 125Z air correction and 65 aux jets. The original 30PICT2 had 120main, 125Z air correction and 55idle - no aux jet.

I had an original vac advance distributor with a knackered vacuum can. So in all my "wisdom" I thought I would put a cheap copy 009 distributor on to get me by. I could not get it to run properly at all. Hesitation, backfiring, popping etc. Using a timing light the advance was dancing around and inconsistent, and timing it to 30deg it would only fall back to about 15deg at idle.

Anyway found an old distributor with a working vacuum can and cannibalised it to rebuilt my original one and now it runs awesomely with the H30/31.
So I would definitely check your dizzy for correct advancing using a light.

Haven't done much running with the H30/31 (car isn't registered - so only round the block a couple of times) but my guess is the 50idle needs to be increased to 55 (like the original) as it seems to lack a bit of power around 2000ish rpm.

Cheers,
Mark

No I do appreciate your help. All these things are SLOWLY elimating issues. I did confuse the fuel dump tube for the idle jet, but now understand.
So far since we last spoke. I check cleaned and changed the following jets in the carb.

Main jet in bowl- Was 120 now 125
Air Correction jet- 125
Idle Jet- Was 65 now 55
Aux Power- was 50 now 65

New gaskets were applied to carb before refiting. Car started beautiful. It Did Not fix the flat spot hesitation on Acceleration.
Also it seems now the "Volume control screw" on Side of carb does nothing. I can wind it all the way in or all the way out and it
has no affect on the running of the engine.

I pulled the spark plugs out this morning. 3 of them had black dry "Soot" on them,which i have seen before. But cylinder 2 spark plug,
had a black "Wet" oily residue on the end.

(Far plug on right hand side-alot cleaner its was wiped clean before photo)

In the "Gregory Manual" its says pulley mark on left is 7&1/2 degress BTDC ,,mark on right is 10degrees BTDC. Looking at picture below... Not sure... to me it looks like 3 triangle shaped marks.

If the oily appearance of plug is fuel (not oil), plug on cylinder 2 isn't firing... The unburnt mixture is popping when it reaches the hot part of the exhaust.
Can check by turning over engine with plug out and look for spark at plug.
Not sure if those plugs are the right type?
The large Notch on left is zero (TDC). If timing has been set to that, it will be very retarded. This will allow easy starting and idling, but poor performance off-idle... sounds familiar. [That large mark is used when setting valve clearances.]
The centre notch is 7.5deg BTDC, the RH one is 10 BTDC. Set timing, statically on No. 1 firing position (rotor pointing to notch on distrib. rim), to BETWEEN 10 and 12.5 (an imagined mark further to right same distance again) for now. (Might run happily later anywhere between 7.5 and 12 depending on other factors). If

OK yep makes sense Brutus. I didnt even think to smell it. Maybe?? ....if i clean them, them put plugs back in.
Give it a quick run, and see if the same thing occurs. Just an idea.

The plugs are NGK B5HS , Dont really know the specs in regards to heat range and so on. They have worked great for me before,
and i can get them in town.

Thanks Joel, didn't know that... Ahem, think I bent or broke one once trying to stop it hitting!

Don't know anything about standard-reach NGK plugs (have used various long-reach ones in later engines and they all seemed excellent).
The correct standard plugs should include:
1. Bosch "W8AC" (Old designations were W145T1, or W175T1, or even W225T1) [145 being warmer than 175; but the newer Bosch system goes inreverse.]

2. Beru "14-8AU Z 68"
All these should be set to ~0.60 mm gap (0.024 inch, or 24 thou.), at least initially as they will fire more reliably.

Cleaning may do more harm than good... We always put new ones in, and use Cu-grease, eg. "Wurth CU 800" (or moly grease, eg. "Molykote", or graphite grease, eg. 'NeverSeize') on the threads. [High temp. wheel bearing grease will do if nothing else...]
Don't use Champion plugs.

Well i Checked all spark plugs after cleaning soot off and all of them were getting spark. I them install them all and started the car.
Revved its guts out with no pop or backfire.!!!!!!! WOOOOO... So im thinking its the plugs. Although this has happened before.
So whether something is occuring that results in the plugs not sparking as good. I replace them and are good for a while and same thing happens again. I dont know.

But for now it is running heaps better.

I also put the pulley to TDC, the rotor on dissy mark for cylinder 1 , connected the earth of test light to earth on coil.
And then connected positive to engine block. IT lit up. When i moved the pulley it went out.

I also put timing light on the pulley,At very high revs the mark is just at where the belt leaves the pulley.
But that dissy doesnt advance on low revs , so now i understand. Why there is a flat spot on low revs or low accelartion.
especially when that carb was/is very lean, would have been nice to know that when i bought them both

i can add a video if you would like to see.

Don't set the timing to TDC. Use 7.5 to 12.5 BTDC initially.
Use the crankcase join/crack as the ONLY reference point. Start with marks well to left of join, rotate pulley Clockwise, & see where bulb goes out.

Points should be gapped to 0.014 - 0.018 inch (approx. 50 deg. dwell on meter).

Everything else needs to be right before setting the carb. speed & mixture.

The plugs might be unsuitable, or faulty, and progressively fouling??? Stop Press: Just found this ref., apparently they are OK for VW:-

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

I havnt touched the timing just looked with the timing light. not sure how to adjust it yet.
The disttributor doesnt have points.
Yeh that is where i read about the NGK plug being ok, rob knows his stuff.
but i am thinking of getting some Bosch "W8AC if i can find where to buy some.

Static timing with a test light only applies with stock distributors.

You cant static time a mechanical dist like yours and call it done, you need to need to put a strobe on and set it for max advance because the quality of them is so hit and miss, some over advance, some advance not enough.

Maxing out at 30 degrees is ideally what you want with a 009.

I read those links you posted and I'm affraid thier tuning advice is incorrect. Mainly the mixture screw setting saying sweet spot and then 1/2 turn leaner....wrong, sweet spot is it, usually there is a sweet window, I favour the richer side. He also confuses himself on Volume screw and Air bleed screw, beware.

W8AC are still available online - try justkampers
Other than that I believe that W8AC have been superceeded by WR8AC and is all that is available in most of the big chain stores.

Not exactly sure what the differences between the two are but I think the new ones have an inbuilt resistor.