[Diy_efi] Re: small engine spark timing

[Torbjörn Forsman]

For many years, i have thought about some simple kind of ignition 
advance on cheap small engines. But of course it must be a very simple 
system, free from the "Rolls Royce syndrome". One possible way would be 
making a simple CDI system using the primary winding of the original 
flywheel magneto ignition coil for charging the capacitor (probably via 
an external transformer or DCDC converter). Then, two inductive pickups 
for triggering the thyristor, one for a late ignition timing for 
starting and one for an earlier fixed timing which is used when the 
engine is running. A good idea of how to arrange the inductive pickups 
can be taken from Briggs&Stratton's breakerless ignition system.
As those engines usually have a high idle rpm (typically 1500-1800), the 
switchover should take place slightly below normal idle (perhaps 
1000-1200 rpm).

Best regards

Torbj?rn Forsman

James W. Harris wrote:
>>If this Kohler is like mine (16hp K34(?) in a 310 Bobcat) the timing is 
>>set by the point gap and the adjustment is very touchy, must be done 
>>with the engine running as opposed to a feeler gauge. A little reduction 
>>in timing can result in a noticeably large loss of power also.
> 
> 
> I've got a Kohler in a Cub Cadet 129 and have found Bob's comments to be 
> right on!!!!  The point cam must have a slow ramp, because a very, very 
> small adjustment makes a difference in no-start / kickback on starting / 
> no power / power improves as the engine warms up.  A crank triggered 
> system on this engine would be able to provide a big improvement, but who 
> knows how much power these typically splash lubricated engines can 
> tolerate.
> 
> Could use single chip HC11, my homemade controller might be a good 
> starting point:
> 
> http://personal.myvine.com/~jhlh/
> 
> So many machines, so little time!
> 
> JW
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