I have a ryobi 26cc, that I'm trying to convert to CDI ignition, but I have no success yet.

I have the sensor located so it will spark when the piston is in it highest position making compresion TDC, but I have no success to turn this engine on or even try to.

have anyone tried to do a similar conversion?

Any help will be apreciated.

Hi, I thing that trying to ignite at TDC is complicating things for you, the spak should occur before it hits TDC at about 28 degrees, well that is on a 2 stroke gas engine and I think it would be similar on a four stroker, try to move your sensor by rotating it to clokwise about 3/8 to 1/2 inch so it ignites before it hits TDC and see what happens

28 degrees is the basic setting, the unit I assume will retard it more to make starting easier. Wow a pusher, what is it going on?

I am not familiar with the Ryobi 26cc, but if you are trying to run it opposite to it's original rotation, it won't work. You can do that with piston ported or reed valve two strokes on CDI ignition (reverse the rotation), but not on four strokes....

AV8TOR

remove the spark plug and turn it thru (be sure the battery for the ignition is on and charged). Ground the base of the plug against the engine. Verify that it DOES spark! Timing is not relevant at this point. If it does, reinstall the plug and proceed to adjust timing (I think 28 degree advance to idle is a LOT for a 4-stroker, your ignition box is probably and auto advance unit, try an intial setting at about 10 degrees and experiment from there). If it FAILS to spark you may have -

a bad ignition unit
a bad battery/switch
a bad hall sensor
the trigger magnet mounted upside down (THIS is the most likely problem)

If you are getting spark, it may be more likely that you have a FUEL issue... Fuel (proper mixture of air) + compression + spark WILL EQUAL detonation!

Hall sensors are North/South sensitive, they only trigger one way. If you have the magnet mounted backwards, it WILL NOT fire... You can try removing the sensor and passing a magnet over it to verify this. Holding the magnet one way will fire, turn it around and it will not.... BTW - the magnet needs to pass pretty close to the sensor pickup, within 1/16" is nice... A strong magnet is desired. Radio Shack sells some little neodymium ones that are about 1/8" diameter and about 1/16" thick. The work very nicely and are cheap.

You are correct about everything except the desired timing number of degrees. The "auto advance" ignition units are actually auto retard. You set them at 28 degrees. The timing retards for starting and idling, and then advances, achieving the actual 28 degrees you set it at when the engine hits around 3 to 4 thousand rpms on most units. At super slow rpms, such as when slowly turning the engine over by hand, the timing is advanced so that you can set the desired total advance. When the engine is cranked to start, and/or idling, the timing is retarded.

AV8TOR

Ok, the engine is rotating like it normally does, I have good spark, but I think the timing is way off.

When the piston is on top and it starts to go down it when I have my spark set. Should I set my spark before it TDC and full compression?

Yes the spark should go off on the upstroke of the compression stroke (both valves closed) about 28 degrees BEFORE TOP DEAD CENTER. The ignition timing should be very similar to a 2 stroke.

Note that 28 degrees would be FULL ADVANCE, and would only be there at higher RPM's but this is your base timing (if your EI unit is auto retarding). They do make both kinds of ignition modules (auto retarding and auto advancing)

An auto advancing EI unit would be set at 2-5 degrees BTDC (or there about).