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bnam
Samba Member
Joined: July 02, 2006
Posts: 2936
Location: El Dorado Hills CA/ Bangalore, India
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 Posted: Thu Mar 23, 2023 6:41 am Post subject: Jumping timing - causes? |
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I have a 71 1600. IT's a euro model that came with and still has twin carbs (unlike US models). I have rebuilt the carbs and have a new restored (by a samba expert) matching distributor.
The car has been timed to 0deg per spec. But, the timing mark bounces around at idle - more than in my other cars (which have engines I have rebuilt - while this one has a non-rebuilt engine).
I did notice that the dwell was at 56deg vs. the 44-50 spec. Will reset that this weekend as my feeler gauges are in my shop. The plug wires have all measured correctly (950-1020ohms). Distributor/condenser, etc are new as mentioned.
What could cause the bouncing timing? Dwell is steady btw.
At 900rpm, I do have the oil light on - it does go away at 950. Worn engine I'm guessing, but perhaps can be continued to be used with slightly heavier oil. Or a weak switch possibly?
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1971 1302LS Convertible (RHD) owned since '74
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1965 Karmann Ghia Coupe - under restoration
1966 Fiat 1500 Cabrio (with 1600 Twin cam)
1952 Citroen TA 11BL |
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sjbartnik
Samba Member
Joined: September 01, 2011
Posts: 5998
Location: Brooklyn
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| Posted: Thu Mar 23, 2023 8:33 am Post subject: Re: Jumping timing - causes? |
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Bouncing timing can be caused by a worn out distributor and/or excessive crankshaft end play (because the distributor drive gear is driven by a gear on the crankshaft).
Since your distributor has been rebuilt by one of the Samba folks I'm suspecting the latter.
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1965 Volkswagen 1500 Variant S
2000 Kawasaki W650 |
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bnam
Samba Member
Joined: July 02, 2006
Posts: 2936
Location: El Dorado Hills CA/ Bangalore, India
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| Posted: Thu Mar 23, 2023 8:57 am Post subject: Re: Jumping timing - causes? |
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| sjbartnik wrote: |
Bouncing timing can be caused by a worn out distributor and/or excessive crankshaft end play (because the distributor drive gear is driven by a gear on the crankshaft).
Since your distributor has been rebuilt by one of the Samba folks I'm suspecting the latter. |
Hadn't thought of that. If there is excessive crankshaft end play, would I be able to see the light forward and aft movement in the rear pulley as I check timing? I hadn't seen any but I didn't think to look for it either.
_________________
1971 1302LS Convertible (RHD) owned since '74
Click to view image
1965 Karmann Ghia Coupe - under restoration
1966 Fiat 1500 Cabrio (with 1600 Twin cam)
1952 Citroen TA 11BL |
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sjbartnik
Samba Member
Joined: September 01, 2011
Posts: 5998
Location: Brooklyn
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| Posted: Thu Mar 23, 2023 10:18 am Post subject: Re: Jumping timing - causes? |
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If you can see it it's WAYYYY out of spec.
It's harder to check in a Type 3 because you don't have easy access to get your hands on the crankshaft pulley.
On a Type 1 you can just grab the crank pulley and shove it fore and aft. If you can feel/hear any movement, it's too loose. If you can see the movement it's well and truly shot.
On a Type 3 you have to check it with the engine out at the flywheel end. The spec is .003" to .005" of end play with a wear limit of .006" though many people have run engines successfully with a lot more end play than that.
But on engines with excessive end play, the fore/aft movement of the crankshaft in the case will cause the timing to jump around.
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1965 Volkswagen 1500 Variant S
2000 Kawasaki W650 |
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KTPhil 
Samba Member
Joined: April 06, 2006
Posts: 34021
Location: Conejo Valley, CA
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| Posted: Thu Mar 23, 2023 10:30 am Post subject: Re: Jumping timing - causes? |
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You wont see it. On a bug where you have good access to the pulley, you can shove it forward and backwards and feel/hear the slight clunk. Tough on a Type 3 though.
Also, excessive end play means you risk wearing out the case at the thrust bearing, adding $1000 to your rebuild cost. I waited and this was my punishment.  |
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bnam
Samba Member
Joined: July 02, 2006
Posts: 2936
Location: El Dorado Hills CA/ Bangalore, India
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| Posted: Fri Mar 24, 2023 12:03 am Post subject: Re: Jumping timing - causes? |
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I think I have found the cause.
This morning, I reset the points to 0.4mm (44deg dwell) and started to reset the timing. I noticed that the jumping only happened at the lower speed and seem to coincide with voltage fluctuation. This car has a dynamo paired with the original mechanical VR. So, I got a spare battery and powered my timing light from that source - the fluctuation stopped. My light must be sensitive to lower voltages.
_________________
1971 1302LS Convertible (RHD) owned since '74
Click to view image
1965 Karmann Ghia Coupe - under restoration
1966 Fiat 1500 Cabrio (with 1600 Twin cam)
1952 Citroen TA 11BL |
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sjbartnik
Samba Member
Joined: September 01, 2011
Posts: 5998
Location: Brooklyn
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| Posted: Fri Mar 24, 2023 10:59 am Post subject: Re: Jumping timing - causes? |
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Well that is certainly a much easier and cheaper solution. 😄
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1965 Volkswagen 1500 Variant S
2000 Kawasaki W650 |
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Bobnotch
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Location: Kimball, Mi
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Nate M.
Samba Member
Joined: August 11, 2003
Posts: 1306
Location: Anacortes, WA U.S.A.
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| Posted: Sun Mar 26, 2023 7:07 am Post subject: Re: Jumping timing - causes? |
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One thing to also look at, is the spring that goes on the top of the distributor drive gear. If it's missing (which is more common than you may think) this will cause timing to jump around at low speeds. That spring is supposed to keep the drive gear seated in the bottom of the case bore. If it's missing, the drive gear will be forced UP as the motor spins. At low speeds it will move up and down causing your timing to fluctuate badly. It typically will only make this happen around idle. As you rev the motor it gets forced UP and the timing smooths out. Something else to check. . .
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jb17atita
Samba Member
Joined: June 06, 2010
Posts: 58
Location: Caracas, Venezuela
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| Posted: Mon Feb 05, 2024 4:51 pm Post subject: Re: Jumping timing - causes? |
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| Nate M. wrote: |
| One thing to also look at, is the spring that goes on the top of the distributor drive gear. If it's missing (which is more common than you may think) this will cause timing to jump around at low speeds. That spring is supposed to keep the drive gear seated in the bottom of the case bore. If it's missing, the drive gear will be forced UP as the motor spins. At low speeds it will move up and down causing your timing to fluctuate badly. It typically will only make this happen around idle. As you rev the motor it gets forced UP and the timing smooths out. Something else to check. . . |
Not to hijack the thread
Is it possible for the timing to jump a few degrees over time?
It retards itself in a matter of day. I have to loosen the clamp advance the dizzy to get it back to 7,5 BTDC.
Could these be any of the causes? Absent spring, faulty dizzy gear, or may be, the dizzy gear has been jumping teeth?
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Tram
Samba Socialist
Joined: May 02, 2003
Posts: 22728
Location: Still Feelin' the Bern- Once you've felt it you can't un- feel it.
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| Posted: Mon Feb 05, 2024 5:51 pm Post subject: Re: Jumping timing - causes? |
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| jb17atita wrote: |
| Nate M. wrote: |
| One thing to also look at, is the spring that goes on the top of the distributor drive gear. If it's missing (which is more common than you may think) this will cause timing to jump around at low speeds. That spring is supposed to keep the drive gear seated in the bottom of the case bore. If it's missing, the drive gear will be forced UP as the motor spins. At low speeds it will move up and down causing your timing to fluctuate badly. It typically will only make this happen around idle. As you rev the motor it gets forced UP and the timing smooths out. Something else to check. . . |
Not to hijack the thread
Is it possible for the timing to jump a few degrees over time?
It retards itself in a matter of day. I have to loosen the clamp advance the dizzy to get it back to 7,5 BTDC.
Could these be any of the causes? Absent spring, faulty dizzy gear, or may be, the dizzy gear has been jumping teeth? |
Your point rider is wearing, either due to lack of lubricating grease on the distributor shaft or they are cheap points. A narrower point gap can retard the timing slightly.
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jb17atita
Samba Member
Joined: June 06, 2010
Posts: 58
Location: Caracas, Venezuela
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| Posted: Mon Feb 12, 2024 6:13 pm Post subject: Re: Jumping timing - causes? |
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| Tram wrote: |
Your point rider is wearing, either due to lack of lubricating grease on the distributor shaft or they are cheap points. A narrower point gap can retard the timing slightly. |
Nevermind. Found the culprit.
Turns out that that the dizzy shaft was spinning... in two parts separately.
The retard was way off. By more than 10deg off.
Already replaced it.
Thanks anyway.
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1969 German Type 1 aka "Atita"
https://www.youtube.com/channel/UClTz_Djcr87yrOa8Iy0dZ2A/ |
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heimlich
VWNOS.com
Joined: November 20, 2016
Posts: 6621
Location: Houston, Texas
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| Posted: Tue Feb 13, 2024 4:39 pm Post subject: Re: Jumping timing - causes? |
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| jb17atita wrote: |
Turns out that that the dizzy shaft was spinning... in two parts separately.
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Easy to spin if not tightened down. When you set the timing take a paint marker so you can see if it has moved. Anything that will stick and stay to the metal will do. A torque marker will work as well. It doesn't take much to keep these from moving.
If you remove the distributor and turn the gear at the bottom with your hand it should be easy to turn and not need a wrench.
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jb17atita
Samba Member
Joined: June 06, 2010
Posts: 58
Location: Caracas, Venezuela
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| Posted: Wed Feb 14, 2024 4:56 pm Post subject: Re: Jumping timing - causes? |
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| heimlich wrote: |
Easy to spin if not tightened down. When you set the timing take a paint marker so you can see if it has moved. Anything that will stick and stay to the metal will do. A torque marker will work as well. It doesn't take much to keep these from moving. |
I'm not referring to the distributor body. It's the shaft itself. It's like taking the dizzy by the gear and by the rotor and rotating them... Independently. 
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