HSSK50 Timing

[Cobrargc]

What is the relationship betweeh TDC and the flywheel magnets? The punch mark on the crank gear is lined up with the hobbing hole on the cam gear. I believe the engine is in time. Yet at TDC the center of the flywheel magnets are at 1 or 2:00 in relation to the coil at 12:00. Do I have something fouled up?

[bobodu]

Download AND SAVE this shop manual....it will tell you everything you need to know about the L-head Tecumsehs
Except how to stop them from hunting....
http://www.cpdonline.com/692509.pdf

[T-Man]

Cobra,

Is this HSSK50 solid-state ignition or points/condenser?
The flywheel spins in a CW rotation. When piston is at
TDC on a solid-state coil system....flywheel magnet will
be at the 1-2PM location. If this is a timeable points and
condenser system....your timing MUST BE ACCURATELY
SET for system to work properly. In the "good ole days",
often a timing/ignition problem was mistakenly diagnosed as a
carburetor problem. As I've said MANY times before, this is a
very tedious procedure, and requires an ability to be able to
MEASURE distance from piston to TDC very precisely for this
system to work optimally. I enhanced and improved my ability to CUSS
working on these over the years.

T-Man

[38racing]

Cobra,

Is this HSSK50 solid-state ignition or points/condenser?
The flywheel spins in a CW rotation. When piston is at
TDC on a solid-state coil system....flywheel magnet will
be at the 1-2PM location. If this is a timeable points and
condenser system....your timing MUST BE ACCURATELY
SET for system to work properly. In the "good ole days",
often a timing/ignition problem was mistakenly diagnosed as a
carburetor problem. As I've said MANY times before, this is a
very tedious procedure, and requires an ability to be able to
MEASURE distance from piston to TDC very precisely for this
system to work optimally. I enhanced and improved my ability to CUSS
working on these over the years.

T-Man

would timing cause a surging under load but not at no load?

[Bruce]

I'll try to answer the OP's original question. The relationship between the magnets and the spot the points open (this would be on an old adjustable timing engine) is important. The old mag guys called this e-gap or edge gap. It is the distance the coil lamination edge is from the edge of the magnet.

At the perfect e-gap you have maximum saturation of the coil with magnetism and this gives you the maximum spark when the field collapses (points open). To wide and e-gap and you have a weaker spark as the magnet is already past the lamination. I know this was very important on setting up the old removable mags like Wico and Fairbanks-Morse. Of course on a modern engine this is all taken care of by the relation of the flywheel key to the flywheel magnets. On older Tecumseh engines it is the reason that timing is critical to not only the correct measurement BTC, but also the correct e-gap, which is not adjustable on small engines and in fact is handled by the electronics inside an electronic ignition system - Bruce

[supertech]

You are confusing Valve timing with ignition timing. Two different things. Valve timing relates to the valve openings and piston position. Ignition timing is related to 'spark' and piston position.

[Cobrargc]

The ignition is solid state, so it looks like the 1-2:00 position is good. I had thought the magnets passing by the coil would occur closer to TDC. When does the coil actually fire the plug? It looks like the plug would be firing well before TDC when rotated CW.

[T-Man]

OK...now we know "SOLID STATE". Usually, Cobra, the only thing that would
change this positioning is a sheared flywheel key. If, @ TDC, the flywheel magnet
is anywhere other than the 1-2 o'clock position (with coil being @ 12 o'clock), the
key is first place to look. If you are experiencing a misfiring, backfire, or feel
the plug is firing at wrong time....first thing, REPLACE PLUG. If that has no
change on things....then I'd look for a grounding problem somewhere....broken
wire, bad killswitch or killswitch is arcing to ground. May I "ADD", Cobra, to the
flywheel key statement....in VERY RARE cases, the crankshaft gear CAN SPIN on
the crankshaft itself. These gears are press-on fitted, and once in a blue moon....
you may see one that's come loose. In the 20 years I spent promoting/selling Brand
T....I only saw this maybe 5-6 times.

With regard to valve timing vs ignition timing.....the two go HAND-IN-HAND on
the older points/condenser systems. If plug fires at improper time in the cylinder,
everything else is affected, also. If valves are not sealing, compression is lost, and
even when there is good spark, engine won't run because of this loss of compression.
It's a VERY FRUSTRATING experience on the older machines with this magneto system.
Determining the culprit on these is the key, but....I've seen folks ponder over them for HOURS
AND HOURS....only to replace the carburetor to fix an ignition timing problem. THIS
is WHY....I have NO hair.

T-Man

[Bruce]

What he said.

As a follow up to my confusing explanation of e-gap above. Remember when mowers had points and you partially stripped the flywheel key, you had no spark. It was the e-gap misalignment that caused this.

On the newer solid state systems (notice I said newer, the old HH160 systems are not that way, they have timing pins), they keep firing even with a totally stripped flywheel key, just way out of time. The reason for this is the e-gap is handled electronically inside the coil. When the coil reaches a certain saturation point, it fires no matter where the piston and crankshaft are.

I know it took me awhile back in 1983 when the Briggs magnetron first came out to figure out that just because the engine had spark didn't mean it was in time. The old way of no spark and then check the flywheel key was gone forever. I went to the school of hard knocks. Now everyone should be really confused - Bruce

[Cobrargc]

Thanks the help and education!