Lauson T651 Ignition Timing

[Buccaneer]

Anyone know any timing specs or procedure to set the timing on the subject motor?

This 4 cycle engine has “fixed” timing, but does have slots in the coil plate to adjust
the timing, before it’s bolted down.
I presume there should be a BTD center specification when the points should open.

Now that the heads are on and torqued down, I’m not sure how accurate a guy
could find TDC, especially with angled spark plug holes.

There was a punch mark on the coil mount plate and crankcase housing, so for
now, I re-aligned them, and hoping for the best.

The manual I have is pretty much just a parts manual.

Thanks for any info.

Prepare to be boarded!

• This topic was modified 2 years, 6 months ago by Buccaneer.
• This topic was modified 2 years, 6 months ago by Buccaneer.

[Buccaneer]

As I was browsing the parts manual last night, I had a epiphany,
realizing in my haste to get the motor back together, that I forgot to set
the valve lash.
I soon found out that the heads needed to come off to do so, and after the
valve stems were shortened to get them back to specs, I decided to
check the ignition timing, as long as the heads were off.
I know of no other way to tell where TDC on the pistons are, as the spark
plug hole is angled, and over the valves, not the piston.

In looking it over, I found another set of punch marks on the opposite side
of the coil / mag. plate, and I’m not sure either set is the correct ignition timing.
The points are set at .020 per manual, and there’s no other timing information given.

I seem to remember some small engine manufactures gave timing information
in degrees of crank rotation before top dead center (BTDC), piston travel BTDC,
or both.

I hooked up my ignition “buzz box” on the mag plate to know when the points open,
and set up a dial indicator.
The closest I can get the points to “open” is .023 BTDC, by moving the mag plate on
it’s slotted hold down.
Neither set of punch marks are lined up at this point.

To further confound things, I just discovered that this twin opposed motor (with one coil) is one of those
“wasted spark” motors. When both cylinders are at TDC, both cylinders will spark, but only one
cylinder is charged with fuel, and the other cylinder has it’s exhaust valve open.
180 degree rotation, and the other cylinder is charged with fuel and ready to fire at TDC.

It would be nice if someone had some timing specs or procedures, but lacking that,
I’d be grateful for any thoughts on “winging it”.

After tomorrow, it will be a few days before I can reply.
Thanks!
https://youtu.be/dJ8NkjiYRDY

Prepare to be boarded!

• This reply was modified 2 years, 6 months ago by Buccaneer.

[Tom]

Buc,  you posted something three years ago on this page.

https://www.aomci.org/forums/topic/1952-lauson-sportking-s-351-need-some-info/

Maybe the single and the twin are timed the same?

T

[Buccaneer]

Tom, I never thought to look in the Lauson single manual.
I found lots of useless tidbits on Lauson searching Google,
but not my own post from back then!

I did look in the Antique Outboarder archives, but
there was only one Lauson page, about early models and serial numbers,
of no use to my quest.

I still have my dial indicator set up, so tomorrow I’ll see if either set of punch
marks line up when the piston is 5/32 (.156) BTDC.
Thanks!

Prepare to be boarded!

[labrador-guy]

Buc I realized that your motor must be alternate firing as soon as I saw the cam shaft.  Anyway the marks to set timing are probably on the flywheel.   Motor needs to be timed with the flywheel on.  Set you dial indicator at top dead center rotate the crank shaft counter clockwise and your buzzer should sound off  when a mark on the flywheel aligns with a mark on the backing plate.  Set the one set of points to 20thousands then set the backing plate to alignment marks hopefully you can find them.   I must have done hundreds of little motors like that.   Snowmobiles and motorcycles.

hope this makes sense!

dale

[Buccaneer]

Dale, I don’t remember seeing any marks on the flywheel, then again, I don’t remember looking, lol.
Snowmobiles were the reason I got the “buzz box” for timing years ago, but have found
it handy for outboards as well.
Heading out to the garage in a while, but it’s “crunch time” …….. heading for Tomahawk
tomorrow A.M. early.
Will let you know what I find out on the timing. Thanks!

Prepare to be boarded!

[Buccaneer]

I played around this morning and set the ignition timing on this twin cylinder, per
the single cylinder manual. Not sure if it’s correct, but it appears by looking at
the old punch marks, that’s what the last guy did.
It was a finicky set up with the magnetic dial indicator, as every time the mag plate
was tapped to change the timing, the indicator would have to be re-set for TDC.
In the end, I got it set within .004 of piston travel.
I’m guessing that’s close enough, seeing how it seems the manual would have you
use a ruler and set the points to open 5/32″ before TDC.

Haven’t got the flywheel on yet to check for spark, but I have a noticeable improvement
in compression after resetting the valve lash.

Prepare to be boarded!

[frankr]

I hesitated to say this, but back in the day, we just went by a rule of thumb that the points should break 1/8″ BTC.  Fanciest tool was eyeball, or perhaps a ruler.

[labrador-guy]

frankr wrote:

I hesitated to say this, but back in the day, we just went by a rule of thumb that the points should break 1/8″ BTC.  Fanciest tool was eyeball, or perhaps a ruler.

Frank your 1/8″ would be darn good place to start.   We used to set most snowmobile engines at 20 thousands.   Most of those engines had centrifugal advance that went to full advance once the motor started .120  (1/8″)!   Now a days all timing is set at maximum and it can’t be changed.   Plenty of racers that run the K series Mercury motors push the timing full advance and wire it down.   I used to run my points a little wide (wide points advance timing),  backing plate all the way and sometimes I got a nice hole in the top of the piston!  BUGGER!   Leaded gas at 100 octane helped that problem!

dale

Tomahawk on Wednesday!

[Buccaneer]

I hope Lauson’s 5/32″ timing spec was the optimum for power and not overheating!
I’ll just be happy if it starts.

I got the flywheel on, and happy to say it has nice spark.

I’m glad I was just checking spark and not trying to start it.
Note the prop in the second photo!

Prepare to be boarded!

[Author]

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