Adjustable timing

[uspmale]

Most Engines, past and present use one to three types of adjustable timing. Some use all three.
They are vacuum. mechanical and electrical.
This is to create spark at different intervals depending on load, temperature and RPMs.
What works well at idle, can make an engine weak at high revs.
This has been used for over 100 years mostly by mechanical means.
When working with 2 stroke outboards, you will find the ignition timing is an incredibly large degree sweep.
Honda spree uses the CDI to advance the curve needed for everyday consumer driving.
To tweak one for race applications is complex and very expensive can find these(chips) or performance cdi ignitions available at some speed shops.
But with a Spree budget I thought I would do a cheap but effective mechanical advance system. Spree uses a magnetic sensor right below the stator to tell the cds when to fire. By moving the sensor about 3 degrees in ether direction, one can advance or retard the timing at your discretion. Right now, I adjust it 3 degrees retarded and found a faster rpm from idle to full rpm. Don't have a tachometer right now but it would complete the tests needed for top rpm.A wireless induction tach would be my first choice, for it portability.
I've got a milk jug full of sensors, so I experimented with a few and came up with a solution with a dremel tool, slotting out the sensor mounting tabs with the curvature of the rotating flywheel. vo-la.Works great!
2 stroke engines can take a lot of variance in timing. The only thing you don't want is extreme advance, causing very tight starting and pre ignition that could damage piston and blow head gaskets.Too retarded and overheating could result.
For adjustability a cable could be attached and run up to the handle bar area for complete range control, but that's a lot of mess around with cables, clamps, sliding mounts etc. So I'll stick with KISS.(keep it simple stupid!) I like basic simple applications, one of the reasons I love Spree's.
If anyone has a wireless tach for sale, let me know,greg

[noiseguy]

Greg,

Can you email me a pic of what you did to the ignition advance?

Did retarding the ignition increase power or just run-up on the stand?

[uspmale]

Only bench checked at this time. Like you Waiting for some better temps to test out all the mods on the street.I'll stop at the shop this weekend and take some pics. Thanks, greg

[JF]

That's an excellent idea for a spree's ignition system; could be very helpful for tuned and tricked out engines. I too thought of doing a similar thing to my express ignition system, but just haven't gotten around to it yet. With the adjustable timing, those who chose to raise the compression won't have that advanced timing problem, which is a plus. This along with the modded carb can definitely improve the overall tuning ability of a spree's engine; and any extra tuneability for a spree is a major plus...

Happy tuning,
JF

[noiseguy]

My thing with this is that from a manufacturing standpoint, you know that these engines would have had the initiator "tang" welded on in slightly different spots, changing the angle at which the plug fires. Not sure how sensitive 2-stroke are to this (maybe not very) but, like you said, it's one more tuning element.

[uspmale]

your answer on the 2 Stroke timing band.......very flexable!
As they say "timing is everything"
Have a good weekend, greg