Aaarrgggh - tuning help!!!

[71Westy]

What a waste of a day. Big plan is to get the 34PICT4 running with a standard setup, including the oil bath filter and a new Bosch SVDA dizzy. So having got it pretty ok (and better than with the 009), I decide on further refinements as it's poor in the cold and still drinks fuel. Cleaned out the oil bath filter with paraffin and petrol (see my other thread - that's not so good either).

So an easy day putting all back together and getting it to run sweet - NOT!

It's now worse than when I started. I just can't get it idling nicely - it hunts between 800 and 1000 rpm, changing every 10 seconds or so. The idle air screw is nearly shut off to keep the revs down and the idle mixture is probably 5 turns out. Set the throttle stop screw as per Rob n Dave's pages (3 thou gap then in half a turn). Tried a different idle jet (same size) from another carb and that was worse - sounded like a tractor! The hunting implies an air leak or a rich mixture. I've searched for a leak - including disconnecting the brake servo pipe - but I can't find one.

I've set the timing to 7.5* btdc, but that moves around with the idling. And then at 3000 rpm, its over 30* btdc - more like 40*. If I back it off towards tdc, it just runs rougher.

Loads and loads of twiddling has seen it drivable, but changing up a gear, it's hesitant and lurches - just like it did with the 009. Clearly, I fluked it the first time I set it up and now I can't get it back.
So, I'm thinking it has me beat.

Does anyone know of a tumner who REALLY knows about air-cooled in teh Ipswich area? Please?

Nick

 

[71Westy]

And I meat 34 PICT 3

 

[dave]

I ve used a guy called "CARTUNE" a couple of times, got both my beetle and camper running spot on, he also did a couple of motors for mates ( old mg, triumph and pos a porsche 911 ) they have always been happy, he has all the modern kit in his van but is old school and can do it with out.
If not how about Simpson air cooled, near Wickham Market.
There is a local company to avoid like the plague, i will pm details to you.
Hope you get it sorted.

Dave

 

[Grazy]

Echo what Dave has said , i always use chap from Cartune , about £50 but well worth it 8)

 

[71Westy]

Thanks guys. I concur about Dave Simspson, but he's always extremely busy - and I was after a tuning specialist really.

Any more clues on Cartune? I'd heard of them before, but there are several around this area. When I rang one number, they didn't seem to understand air-cooled....

Is it the one tun by Geoff Wright?

Cheers,
Nick

 

[tomedwar72]

Nick,

Do you have one of the paper filters kicking around that you could put on the carb as a temporary measure? If you cleaned the oil bath filter out with petrol it will take a while for it to stop producing extra combustible fumes that will be drawn into the carb. These might well be enough to increase idle revs as you are seeing.

Just an idea, might not be the case though.

Tom

 

[71Westy]

Good thought - but it was doing it before I cleaned it out (hence the cleaaning ).

I've found the Cartune man-in-the-know and he's coming round tomorrow. Fingers crossed he can find the problem!

Thanks,
Nick

 

[Trikky2]

I've set the timing to 7.5* btdc, but that moves around with the idling. And then at 3000 rpm, its over 30* btdc - more like 40*. If I back it off towards tdc, it just runs rougher.

Nick

Assuming you have no air leaks on the inlet and the throttle cable/mechanism is not sticking or holding the throttle slightly open - your problem is this moving timing.

The timing should not change at tickover. Theres only two possibilities. Either your getting the wrong vac signal to the vac advance or the dissy is faulty.

Check to see if the timing moves while ticking over with the vac can disconnected (and the vac takeoff on the carb blocked off).

If it still moves around then you have a mechanical fault in the dissy eg. points/base plate loose or sticking centrifugal weights/missing or incorrect spring or excessive sideways play on the rotor shaft.

If on the other hand the timing becomes stable with the vac disconnected then check the vac can for leaks (it could be letting air get drawn into the carb). At tickover the vac can should not be doing any timing advance - it should only be advancing the timing at slight/partial throttle openings. If the vac can checks out ok then its the vac signal. This may be down to incorrect carb adjustment or possibly a loose butterfly on the spindle.

PS. The way I set the throttle stop is set the screw so its just gripping a cigarette paper eg. you can still pull the paper out without it tearing (you must not be touching the throttle arm when testing the setting with paper). Then turn the screw in another half turn. The stop screw is exactly that. It stops the butterfly jamming in the throat of the carb but should be set so the butterfly is completely closed. The tickover speed is adjusted only with the bypass screw and never with the throttle stop screw.

 

[71Westy]

That's really useful - I was wondering whether the new dizzy was the source of irritation. It hunts whether the vac tube is connected or not. And the timing mark doesn't move at idle (apart from the jumping around) whether its connected or not. It's brand new - so no slop in the bearings - but it might be worth checking the weights I guess.

I have tried to set the throttle stop (only using an 0.003" feeler gausge rather than a piece of paper) as you suggest. Throttle movement is unimpeded. And yes, I've been adjusting tickover using the bypass screw only.

The take-off for the air intake flap is much more meaty than that for the vac for the dizzy - so I am wondering whether that's a problem. But at the moment, that's blanked off just to get the damn thing running.

I suppose a faulty dizzy might also explain the 40*ish advance I'm getting???

Thanks for the advice,
Nick

 

[BJ1]

If your carb is a Bocar replacement then that would explain why the idle is hunting. These crapulous 'carbs' have a built-in idle problem caused by poor manufacture. Not only are the idle drillings often 'swarfed up' but the idle jet is too close to the end of the drilling. You can sometimes sort this by packing out the jet with a very thin washer. Of course if your carb is an OG Solex then all the above is bowlocks :lol:

Have you also checked your spindle bearings? If they are badly worn then the beast will never idle properly.

 

[K@rlos]

Try Dan Leech at Bus Werkes in Martlesham. Here is his business number, 07979845382. If your van will drive, his workshop is down Sandy Lane past Spencers Garage.

Karl

 

[K@rlos]

There is a local company to avoid like the plague, i will pm details to you.
Dave

I've heard about this comapnys Anticks too

Karl

 

[dave]

makes you wonder how they keep going, saw an early shell, looked solid,there in primer dumped in hedge, 6 months later still there. that was last autum, wonder if still there, probebly some ripped off customers!!

 

[71Westy]

Thanks Karl, I'll keep that info handy. Got Cartune coming round this morning.

It is a genuine Solex - spraying carb cleaner round the spindles makes no difference to the running, so I sort if assumed they were ok??? I have a new replacement, but that's much worse And yes, it goes - just hesitant when changing up like it was with the 009!

Nick

 

[Trikky2]

Yes your right, if your getting up to 40 degrees advance from a static timing of 7.5 then theres something wrong with the dissy for sure. The timing light should also not show any change in timing at tickover either.

Its also worth noting that "back in the old days" we used to get bays with uneven running and flat spots which were cured by fitting the main jet and idle jet from the beetle 1600 engines (which were one size larger). For some unknown reason the carbs on transporters were fitted with these smaller jets which made the engine run so lean as to be at the limit of carb technology.

I hope it gets sorted by the expert you have lined up and I would be interested to know what the outcome is.

 

[71Westy]

Well Geoff from Cartune (Ipswich) has just been, and it was worth every penny in terms of just instruction.

He started off using a gas analyser to check what was what.
He widened the points a tad (less than a thou) - by eye! - to get the dwell down from 47* to 39*.
Then knocked the timing back to 5* at idle, which brought the 3000 rpm timing to 38* - he was happy with that....
The movement in timing at idle he thought was down to slack in the drive mechanism and ws a fact of life in VW engines, from his experience.
Then he throughly checked the air cleaner that I've been messing about with.
Hooked up the analyser and went for the tuning. Now the CO was too low (it was too high before!). He ran out of adjustment to get the idle rich enough for his liking, but it was ok at 2.8%. Changing to a different profile needle helped (that's the original back in now) So did a tweak of revving with his hand over the air intake - he thinks that there my be some very slight blockage in the idle circuit.

But the proof of the pudding is that it drives really smoothly now.

He has advised a new carb would be better - and had recently tuned a new one ok. After calling the owner of that one, turns out that was an EMPI - dunno if they're all good, but that one was...

Anyway, I'm happy at the mo - well worth the money!

Nick

 

[Trikky2]

Glad to hear you got it sorted and thanks for letting us know the outcome.

 

[71Westy]

No probs. I was shocked how little the adjustment was to make a big difference.

I''m now gonna play with the air corrector jet to see if that makes a difference to top end power (which seems down) - I've got a 60 spare (its got a 110 in there at the moment). But I'm gonna take great care not to disrupt the good work done by the tuner.

The next problem will be as it drifts out - I have no further adjustment in the carb.

So another refurbed Solex, an Empi, or a Weber 32/36 are on the cards - but which?..... hmmm. I really don't want to go twin carbs,

Nick