ignition timing

[iain2204]

hi there all could someone please tell me the best setting for my timing on my 2.0l Aircooled cu engine as i seem to be getting lots of different answers from people.also could some please explain to me the best way to set it.many thanx to anyone who helps me out with this

[Footprint]

Disconnect the wiring plugs from the idle stabiliser, (the black plastic box next to the ignition amplifier), and plug them together - assuming you have an idle stabiliser that is, many have failed and been removed. Set the timing at 5 degrees ATDC all vacuum hoses connected.

This setting is heavily dependant on the correct idle setting of the carbs, if they're not right the ignition will be impossible to set correctly at idle.

To roughly check to see if the carbs are set right as regards vacuum signals, set the timing as above and put your strobe on the timing marks, open the throttle a dab and as soon as you do you should see the timing jump forward to about 8 degrees BTDC, this means the vacuum retard is getting the right pull when the throttle is shut, and being released when the throttle opens.

If that doesn't happen then the carbs will need basic setting first before attempting to get the timing right.

[California Dreamin]

Some basic settings for Early 2litre (CU) air cooled engine



Vehicle identification Air Cooled CU engine letters
Capacity. 1970cc³
Number of cylinders/type. 4/overhead valve
Production run. 1979-1983
Output. 51kW - 70bhp DIN @ 4200RPM
Minimum octane rating. 91 RON
Ignition system. transistorized hall effect
Trigger location. distributor
Fuel system. Twin Solex carburetor
Type. 34 PDSIT
Description. carburettor - twin venturi
Tuning and Emission
ignition coil supply voltage 11 volts
primary resistance .57 to .75 ohms
secondary resistance 2400 - 3500 ohms
firing order 1 - 4 - 3 - 2
distributor part number Bosch - 0 237 023 007
ignition timing 5°±1° ATDC with vacuum see note at bottom of page
Mech'l ignition advance checks 0°-1° @ 1150RPM w/o vacuum and basic timing
9°-13° @1600RPM w/o vacuum and basic timing
21°-25° @3400RPM w/o vacuum and basic timing
Vacuum check [+] - advance : [0] - Retard
Vacuum range - °engine [+] 9° to 12° : [0 ]11 to 13
Vacuum starts - mbar. [+ ]90° : [0 ]90°
Vacuum ends - mbar. [+] 240° : [0] 200°
idle speed 850±50 RPM see note at bottom of page
oil temp for CO test 60°C
CO content @ idle 0.±.3 % volume
HC content @ idle 500 parts per million
Service checks and adjustments.
Spark plugs Bosch W8CC
electrode gap .6mm
valve clearance hydraulic
compression ratio 7.4:1
oil pressure 2 bar @ 2000RPM
Lubricants and capacities.
Gearbox oil grade 80W-90W
gearbox oil capacity 3 litres
autobox oil grade dexron (final drive type 90W)
autobox capacity 3 litres (final drive capacity .75 litres)
Tightening torque's.
Flywheel use new bolts with locking compound - 60Nm + 90°
clutch to flywheel 20Nm
crank pulley single pulley 60Nm -
rear hub nut 500Nm!
steering track rod end 30Nm
brake caliper to hub 35Nm
brake caliper carrier to hub fixed type caliper 160Nm
Brake disc and drum dimensions.
Minimum brake disc thickness 11mm
maximum drum diameter 253.5mm

Notes.

When setting ignition timing on vehicles with DIS (digital idle stabilisation) the two connectors of the DIS unit must be removed and plugged together.

Disconnect engine crankcase breather and plug on side of air cleaner.

[john1]

Could I jump in and ask a question folks.

Looking at my scale, it has 0 then 4 -12-16-20-24 going left from the 0 and right from the 0. Hope you are with me here.
so found mark wee bit tipex plug two black things together start up. Lead on Number 1 back right as i look at it.

But it reads 23 to the left of the 0 point. Am i doing something wrong?

Thanks in advance yet again

john

[bigherb]

Number one cylinder is Front Right cylinder. The front of the engine is the flywheel end.

[BOXY]

If you're on No1. then either the vac retard isn't working, the throttle gap is to big, or the idle is too high. If you take the cap off the dizzie and suck each of the vac lines in turn you should see the internals move to the left & then to the right. If when you suck the vac lines you get no resistance or nothing moves that will be the first problem. Here's what I did when I was trying to sort my timing out.

Vac lines disconnected & blanked. 850RPM @ 8' BTDC.
Air box vac line connected & a tiny tweak of the dizzie and 850RPM @ 6'ATDC
Carb vac line connected and 1000RPM @ 18-20' BTDC. Ok not right but better than yesterday.

I unhooked the balance bar between the carbs and popped off the connecting rods. Then I backed of the "throttle adjusting screws" until I could see daylight between the screw and the stop. I pulled up on the link rod on the left carb and there was still a bit of movement that closed the gap between the screw and the stop. I gave the rod and throttle flap a squirt of carb cleaner and a wiggled them about a bit. Once they were freed up I wound the adjusting screw one turn past just touching. After putting everything back together the van started and idled at 850RPM @ 6'ATDC and the timing advanced to just over 40' BTDC at +3000RPM. The throttle flap must have been sticking just a smidge too far open at idle letting the vac advance kick in too early.

[john1]

Number one cylinder is Front Right cylinder. The front of the engine is the flywheel end.

ok so as i look from the back its not right hand side 2nd in! its left hand side 2nd in making it front right from flywheel end!

thanks gents

[bigherb]

ok so as i look from the back its not right hand side 2nd in! its left hand side 2nd in making it front right from flywheel end!

thanks gents

The furthest forward cylinder from you on the right.

[john1]

If you're on No1. then either the vac retard isn't working, the throttle gap is to big, or the idle is too high. If you take the cap off the dizzie and suck each of the vac lines in turn you should see the internals move to the left & then to the right. If when you suck the vac lines you get no resistance or nothing moves that will be the first problem. Here's what I did when I was trying to sort my timing out.

Vac lines disconnected & blanked. 850RPM @ 8' BTDC.
Air box vac line connected & a tiny tweak of the dizzie and 850RPM @ 6'ATDC
Carb vac line connected and 1000RPM @ 18-20' BTDC. Ok not right but better than yesterday.

I unhooked the balance bar between the carbs and popped off the connecting rods. Then I backed of the "throttle adjusting screws" until I could see daylight between the screw and the stop. I pulled up on the link rod on the left carb and there was still a bit of movement that closed the gap between the screw and the stop. I gave the rod and throttle flap a squirt of carb cleaner and a wiggled them about a bit. Once they were freed up I wound the adjusting screw one turn past just touching. After putting everything back together the van started and idled at 850RPM @ 6'ATDC and the timing advanced to just over 40' BTDC at +3000RPM. The throttle flap must have been sticking just a smidge too far open at idle letting the vac advance kick in too early.

Vac is ok with dizzy, did the test fine.

I think i need to try the rest now.

I can get the mark down to 5 but she runs poor. put it back to 20 and runs fine,idles fine.

I will give it a go.

Thanks folks great help.

John

[BOXY]

Have you got the vac lines going to the right sides on the dizzie. Easy to get them wrong if they've been off.

Here's the whole sordid story.

https://club8090.co.uk/forum/viewtopic.php?f=39&t=79992" onclick="window.open(this.href);return false;

[john1]

Have you got the vac lines going to the right sides on the dizzie. Easy to get them wrong if they've been off.

Here's the whole sordid story.

https://club8090.co.uk/forum/viewtopic.php?f=39&t=79992" onclick="window.open(this.href);return false;

Cheers for that Boxy,, what do you mean by "the throttle gap is to big"?

The van is running fine just now so i want to make sure I know what im doing before i start playing around.
Why would she run ok with the timing mark showing at 20? I take it thats an incorrect reading due to a set up problem like you had?

[BOXY]

The throttle gap is measured with the carbs off. It's the distance between the edge of the throttle flap and the barrel of the carb. The haynes shows how & where to do it. It's easier to wing it and just adjust the throttle stop screw until they just touch and then one more full turn in. Having a bright torch helps you see when the stop just makes contact. You need to disconnect the link rod when you're doing it to make sure each throttle is free to close independantly.
Check your throttle cable isn't to tight because if it is it could be holding the throttle flaps open a smidge too far and adjusting the stop won't make any odds anyway.

If your timing mark is at 20'BTDC at idle, are you sure your idle is around the 850rpm mark? How far does it advance when you rev the engine?

[tamson]

This all sounds too familiar! The throttle stop screws on my carbs are wound out about half way?! Could it be this is over riding the central idling circuit and hence it won't be possible to adjust the idle using the idle screw ?

[john1]

The throttle gap is measured with the carbs off. It's the distance between the edge of the throttle flap and the barrel of the carb. The haynes shows how & where to do it. It's easier to wing it and just adjust the throttle stop screw until they just touch and then one more full turn in. Having a bright torch helps you see when the stop just makes contact. You need to disconnect the link rod when you're doing it to make sure each throttle is free to close independantly.
Check your throttle cable isn't to tight because if it is it could be holding the throttle flaps open a smidge too far and adjusting the stop won't make any odds anyway.

If your timing mark is at 20'BTDC at idle, are you sure your idle is around the 850rpm mark? How far does it advance when you rev the engine?

Hi Boxy, it does advance but i didn't take a note how far, end of scale poss?? i will check and get back to you.

Edinburgh festival to night so it could be MONDAY! LOL

john

[tamson]

The throttle gap is measured with the carbs off. It's the distance between the edge of the throttle flap and the barrel of the carb. The haynes shows how & where to do it. It's easier to wing it and just adjust the throttle stop screw until they just touch and then one more full turn in. Having a bright torch helps you see when the stop just makes contact. You need to disconnect the link rod when you're doing it to make sure each throttle is free to close independantly.
Check your throttle cable isn't to tight because if it is it could be holding the throttle flaps open a smidge too far and adjusting the stop won't make any odds anyway.

If your timing mark is at 20'BTDC at idle, are you sure your idle is around the 850rpm mark? How far does it advance when you rev the engine?

Ok just got in from tweaking the carbs to basic setting. Fired up and was running sweet idling at 850rpm. However when I turned the engine off then started it again the revs dropped to 650. The only difference I noticed was that there was no air sucking through the pipe on the top of the left carb. Also screwing the idle screw in and out made no difference to the rpms's. Any ideas? Cheers