Weedeater trimmer fl26 no start

[logan01]

Though from an unexpected source and more info than needed, this has an excellent discussion on timing. Beneficial read regardless. 2-stroke timing | Model Engineer

 

[bertsmobile1]

I disconnected the stop switch wires and took the covers off. The flywheel looks OK with no scratches. The magnet is strong. Tried starting with the stop switch wires disconnected but still not a sputter from the machine. One thing I noticed is that when the flywheel magnet is aligned with the coil the piston is positioned before TDC a bit. Checked that with a screwdriver in the plug hole. When the piston is at TDC the magnet is a tad passed the coil. Might that be like timing on a car engine at so many degrees before TDC?

That is correct.
Ignition fires just before TDC

 

[bertsmobile1]

It would be good if we could check timing with a light like on a car. The digging I have done shows that the little 2 strokes which work so hard and well at 7000 rpm do have up to 22 degrees advance at WOT, but I do not know if initial setting is BTDC. Unlike points operated stuff the mags put out a wave that peaks and is used by the circuit in the module to produce spark, so I think it would be hard to static time. But there are 2 stroke guys on this forum who may be able to comment.

Well actually you can if you want to.
Scribe a line on the flywheel at TDC, then measure the circumference from the mark, back to the mark.
Divide this distance by 360 and you have the amount of circumference equal to 1 deg.
Scribe a line at 5 deg increments
Use an induction timing lamp and away you go.

Start the engine with a battery drill on the crankshaft nut if there is nowhere you can mark the lines where they are visible with the pull start on.

However there is little point in this as the timing is not adjustable, unless you are checking that a substitute for a NLA module is firing at the right time.

 

[motoman]

Berts, I am still looking for the ref materials. I have (typically) misplaced them . Logan, I read your reference discussions and interesting they are.


Looking around I did find some "generic" timing curves for small , stock (not race) 2 strokes. At 1000 rpm about TDC-14 degrees BTDC , rising to about 22 degrees BTDC between 3000 RPM and 5000 RPM and then retarding slowly to 14 degrees BTDC through 10,000 RPM . It is interesting that on the small dia (trimmer sized) fly wheels only a small (.028" ) shift in the module position is worth about 8-10 degrees (double check , please). Earlier I had said 20 plus degrees at WOT which is not entirely accurate. Wonder if anyone knows the max RPM of a typical trimmer?. This suggests that any factory tolerance or error in location of the module screw holes can affect initial spark position and ...( not recommending necessarily), some light work elongating the holes could yield some static timing changes, maybe helping starting ?

The patents design of ref I misplaced include advance and retard by way of electronic parts , no points, vacuum or bob weights,