Two timing marks appear under light. Huh?

[720inOlyWa]

When I set the timing on my 85 720, I see two marks appearing under my light, about 10 degrees apart. The engine seems to want to be timed to the left hand mark, but the right one seems brighter and easier to see, to me. Not sure how to interpret this 2 timing mark sitch. Any ideas?

 

Thanks!

 

Marc

 

[dr.feltersnatch]

Pull the cap and see if there is carbon build up causing the spark to jump

[DanielC]

Does your engine have four spark plugs, or eight?

[720inOlyWa]

8 plugs / NAPZ 2.4 gas engine.

It seems to want to run nicely for me, but it just isn’t quite there yet. Mostly, it isa little hard to push of of idle. It just isn’t advancing smoothly and I am trying to track it down. I bet it is one small thing. I am replacing vacuum hoses, checking everything I can. This two mark deal kind of bugs me thoug. I will look at the cap again, but I didn’t see any issues last time I checked.  This is all following a head gasket and timing chain replacement, along with a weber carb install.

 

Thanks.

[bananahamuck]

Does the pulley have notches where both marks are?

[720inOlyWa]

just one pully notch.

[DanielC]

My understanding is the NAPS-Z engine fires the plugs at two different times, for emission control.  I could be wrong. 

 

I am out, because I am really not that familiar with these engines.

[dr.feltersnatch]

I thought it fired both at the same time.

[bananahamuck]

Well i would say the one without a pulley notch could probably be ignored.  I looked at my books i have laying here and it says nothing of multiple pulley notches till the v6

 

(disclaimer) when Sealick comes on he will probabaly prove me wrong  stupid .

:lol:

[Sealik]

There's only one notch on the pulley.

 

Grab a marker(felt pen) or file and 'high light' the single notch

Assuming you have the vacuum advance hose pulled from the dizzy and plugged when setting the timing.

[Sealik]

All 8 plugs should be firing at idle

3-5 degrees BTDC

[datzenmike]

The two coils fire together and only once.

Pulley has a single timing mark at TDC

The saw tooth timing scale is bolted behind pulley near the alternator and is 20 l 15 l 10 l 5 l O

....................................................................................... pulley notch should be about here ^

 

 

There should be no vacuum at idle but won't hurt to have the hose off.

Idle MUST be 750-850 or mechanical advance will upset your reading.

[720inOlyWa]

Major thanks to everyone who responded to my post here. I did a bit of everything that you suggested and worked out my problem! Between the funky cap and rotor and the idle mixture setting being off, plus the odd bad vacuum hose and/or connection, she is running much better now. We firmly have one timing mark displayed now and it is at 3 degrees BTDC.

 

She just sits there idling away like a cute little sewing machine.

 

Thanks, everyone. You can bet that I will be back!