timing?

[marco]

Is it set according to dizzy part no. Or by engine type?
Found info on 'old volks home' site that says dizzy was originally specced for a 1970 auto beetle 1600 which I guess was a single port engine, it's now fitted to a manual bus 1600 tp
Dizzy set to 0 deg @ 800-950 rpm vac disconnected and plugged according to info
Manual states choice of 5 deg atdc or 7:5 deg btdc w.vac disconnected.
What do I go for? Very confused as engine is recon with daft engine no. that makes no sense.
Cheers guys

 

[vwcanuck]

What is the dizzy number/type and carburetor number/type? These are supposed to match the originally specified ones for your engine in order to run most efficiently. Unfortunately over the years owners threw in whatever they could find and if it worked ... it was considered fixed.

 

[marco]

Ok, dizzy no's
JPU-4
(bosch) 0 231 146 101
(VW) 113 905 205 AL

Carb is a solex 34 pict 3
(will get more info this evening off carb)

Dizzy came off a 1600 tp bus engine that had a weird single choke Webber alternative to the solex carb.

 

[jonboylaw]

Set max advance to be 30 BTDC at 3500 then check at tickover with vac removed and plugged carb end to see what you get. Should be close to 7.5 BTDC. Plug in vac tube and it should move the timing to 5 ATDC but quickly move to 7.5 BTDC as you come off closed throttle. If this does not happen then the vac my be leaking, stuck or base plate not moving. If the timing at tickover is much higher than 7.5 BTDC vac off then the centrifugal advance may not be working. The important figure is max advance.


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[marco]

Carb has vw527-7 stamped on it.
Jon, do I set the max with vac connected?

 

[vwcanuck]

Check Glutamodo's link in this thread for matching carburetor to distributor to engine. This isn't law but good to see if you have the original set-up in your bus. If not, it may still work and timing may take more research or listen to johnboylaw's experience ... gold

http://www.thesamba.com/vw/forum/viewtopic.php?t=525857&view=next" onclick="window.open(this.href);return false;

Also ... this provides information about matching the vacuum can with the distributor and engine.

http://images.thesamba.com/vw/gallery/pix/776056.jpg" onclick="window.open(this.href);return false;

Hope this helps someone

 

[jonboylaw]

Unconnected, you will find it pulls more advance when connected, on over-run as you close the throttle, this is perfectly normal but may be confusing when trying to take the max centrifugal advance.

BTW, I am running a crank fired megajolt system and pull 42 degrees max advance on highspeed over run (Max vac (throttle closed) at 5000rpm)


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[marco]

I checked the samba and found that the dizzy is fitted to a few AS engines so I'm happy to use it. I've set it to 7.5 btdc idle, 30 btdc at 3500, as suggested by Jon, still seems to hesitate at low revs and pulls fine from about 1500 rpm. Scratching my head?!

 

[TeamBrian]

Problem with the jets?

 

[jonboylaw]

Two possible reasons (amongst many others), the dizzy is not advancing correctly at low revs (dirty/sticky plate or leaking Vac) or the accelerator pump is not working correctly.
As you are up to speed on the dizzy, try sucking on the vac pipe with the dizzy top off (engine off) to see if it moves some. if not then see if it is sticky or the vac can leaking. If all ok, then check the accelerator pump to see if it is over or under fueling.

 

[marco]

Cheers Jon, the vac seems ok, good suction from the carb, the hoses are new and I gave the dizzy internals a good clean and lube and the vac moves when suction applied, will try the accelerator pump as it doesn't seem to make any difference when on max + or max - . When I got the carb it was set at max (I guess for a 009 dizzy) but hadn't been used for yrs.

 

[marco]

BTW how come there's lots of different size jets on 34 pict carbs but the kit comes with a generic size?

 

[jonboylaw]

Different engine specs and requirements I would guess. They were not just for VWs in the day.


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[67panel]

its not just the main jet,air corrector as well,anyone know the link to the carb data that was on here 2011/2010 ish as that had all the answers.

 

[marco]

Vwcanuck posted a link ^^^ to carb listings on the samba, quite a minefield of carb/dizzy options, :shock:

 

[marco]

Two possible reasons (amongst many others), the dizzy is not advancing correctly at low revs (dirty/sticky plate or leaking Vac) or the accelerator pump is not working correctly.
As you are up to speed on the dizzy, try sucking on the vac pipe with the dizzy top off (engine off) to see if it moves some. if not then see if it is sticky or the vac can leaking. If all ok, then check the accelerator pump to see if it is over or under fueling.

Checked the accelerator pump tonight, not working at all, no fuel being squirted so used the rebuild kit bits off the old knackered carb and voila, lots of fuel, think I've got it set about right, 1.6 ish ml per squirt, the dining room stinks of petrol now. Will refit tomorrow and see how I get on.

 

[jonboylaw]

Excellent, I should say you are up to speed on dizzy and carb systems now


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[marco]

Excellent, I should say you are up to speed on dizzy and carb systems now


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Not sure, maybe more confused than ever :lol:

And I thought old engines were simpler :lol: took 6mths to find the fault on my T4, main dealer couldn't fix it, independent couldn't fix it, ended up being a £50 engine speed sensor that would randomly pack in.

 

[marco]

refitted carb and......NO FLAT SPOT :bliss:
thanks guys for all your help, just need to beg/borrow an exhaust analyzer to get co levels spot on.

 

[jonboylaw]

Congrats! Now go and use the bugger!!!


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