Link & Sync

[James in Canada]

I'm posting this question for myself and for many other people doing a link & sync.

Here is a nice illustration for reference:



I added some letters for easy identification.

A. Max Timing Advance
B. Min Timing Advance
C. Throttle Engagement Point
D. Carb Sync
E. Relationship between Throttle and Timing

On my engine:
Max timing set by Joe Reeves Method - 24 Degrees
Min timing set by Joe Reeves Method - 5 Degrees
Throttle plates just start to move at the first mark
Both throttle plates start to open at exactly the same time.
My question it "E". What is the relationship between throttle
and timing? Should max advance occur at a certain point in
the throttle advancement? I know that max timing advance
is well before maximum throttle. It just seems to me that
there should a setup for the relationship.

 

[James in Canada]

Another handy picture:



F. Throttle engagement point
G. Where the cam should be when you raise the start lever on the remote.
H. What is this mark for? Could it be the point where max timing occurs?

 

[joereeves]

The 4 degree retarding off setting thing only pertains to the full throttle setting. The idle timing setting can be set normally.

To set "E"...............

Assuming that when the metal cam is NOT touching the throttle roller... and both carb throttle butterflies are fully shut.

Have the engine idling and the throttle roller set to the first scribe mark on the metal cam.

At this setting (above), the timing light should register whatever the idle timing is listed at in your service manual.

If the specified timing does not register properly, that nylon yoke requires adjustment.

Keeping it simple... When the carb butterflies are set properly, and the roller is centered with the scribe mark, and the distance between the vertical throttle arm and the nylon yoke is as it should be... the idle timing will register.

 

[James in Canada]

Excellent answer Joe, thank you.
I was aware that the -4 Degrees only applies to max timing.

 

[joereeves]

Excellent answer Joe, thank you.
I was aware that the -4 Degrees only applies to max timing.

I thought you would be... but just in case!

 

[timguy]

Great info. Have you ever noticed how much movement is available as you tighten down the carbs? Often you sync by simple carb mounting tweek.......especially if you know carbs were in sync before your carb removal.

 

[Romeman]

The 4 degree retarding off setting thing only pertains to the full throttle setting. The idle timing setting can be set normally.

To set "E"...............

Assuming that when the metal cam is NOT touching the throttle roller... and both carb throttle butterflies are fully shut.

Have the engine idling and the throttle roller set to the first scribe mark on the metal cam.

At this setting (above), the timing light should register whatever the idle timing is listed at in your service manual.

If the specified timing does not register properly, that nylon yoke requires adjustment.

Keeping it simple... When the carb butterflies are set properly, and the roller is centered with the scribe mark, and the distance between the vertical throttle arm and the nylon yoke is as it should be... the idle timing will register.

Nice post