ignition timing adjustment methods

[highseastravler]

there are several ways of altering the ignition timing
one way is the offset keyway good for about 4 to 6 degrees +or -
then there is the "pole peice modification"
where one grinds off the leading and or trailing edges of the pole peices and you getabout half
the timing change from whay you grind need i say its a onetime adjustment method
and last but not least cutting slots where the mounting screws go through the magnet frame
altough this will allow only 2 or3 degrees change it may be all you need
otherwise machineing a new rotor magnet assembly as the factory one is not a very strong magnet
does anyone have any other good ideas on how togetbettercontrol of the spark in these china motors
and about lighting unless theres a way to seperate the magneto and lighting frames i beleve that
a 2 to 4watt charging circut with batteries is the best hope for good lighting

[AussieSteve]

That only sets the ignition timing for a particular rev range. There is no way to chang the amount of advance to correspond with rpm.
Advance or retard to enhance a particular rev range and others will suffer.

[tommyboy1442]

i have an idea, lets all send jim 5 dollars to aid in funding a billet race block, something he can possibly make for production, and then we can all buy good ol american, and then just ditch the chinee mota.....

[highseastravler]

yes there is a method of making a variable rpm timing adjustment with the equippment provided steve but it involves a staggered gap at the pole peice on the leading edge
and cuttingsome of the trailing edge off
but ive also read in the 2stoke tunes book that small bore engines do not need much spark adance

[highseastravler]

if timing is fixed for most power at lets say 6000 rpm its onlt 66 cc its not going to gripe much about kicking back when trying 2 start now if we had a500 cc bore id want a spark retarder just to get it started but after its running id return it to its advanced position
we dont need much of a active advance curve just a good way to set the spark timing at all 2 would be nice because you dont have to be far off to loose peak power
these chinas were built to run detuned and for $125 they werent concerned about much after that as a matter of fact im shure theyll last a lot longer running a little rich (4 strokin) not getting high revs and not getting so hot trying to put out peak power
were working with popcycle sticks and elmers glue theres only so much that should be done lol

[sportscarpat]

Rotating the magnet or stator with a slotted base seems like an easy way to do it. Is there enough room in there to even do this?

[highseastravler]

i think the easyest is the offset keyway method

[exavid]

It looks to me the timing is set for a good compromise between starting and running. There's no sign of kickback when starting and the engine will run up to reasonable rpms under load. It is possible to improve the engine and get a lot more performance out of it, but there's no free lunch. If you want the bike for reliable long term use the engine is pretty well set up as it is though a bit of cleaning up it's breathing wouldn't hurt. If the compression is raised by shaving the head, re-jetting and running a tuned exhaust the engine will definitely perform better at the high rpm end but that will reduce it's useful life. Higher heat and stress of higher power isn't going to make them last very long. That's without even considering the wisdom of riding at much higher speeds on a bicycle with barely adequate brakes. I don't mind peg scraping on curves and pushing my motorcycles to the limits of my ability but I don't think that's all that great of an idea on a motorized bicycle. The wheels, bearings, tires and brakes just aren't up to a lot of high speed riding.

[AussieSteve]

highseastravler, I think that you misunderstood me. I know there are a couple of ways to alter the fixed advance, what I meant is that it's not possible to get increasing advance with higher rpm.
A pity, because that would make these little engines perform better.

For fixed advance, setting an offset to the woodruff key is the easiest way, but as exavid says, they're already pretty well tuned for all-round performance.

[highseastravler]

there maybe a possible way to gain the benefit of ignition advancement at higher rpm's
if i knew a little more about the coil module "mostly when it decides to fire"
since we have a single coil that both charges the cdi unit and determines when to fire it
"i suspect that it does this at the zero crossing point on the wavefourm "
that point can be minupulated possibly by modifining the pole peice desighn or in modifing the ground wire return circutry with a dc bias voltage if you have any ideas let me know
but tommrrow im trying my staircase ramp on the leading edge of the pole peices and ck with timimg light i did check the stock unit and found timing dead still at all rpms
if its a zero or triggering on the voltage as the second half of the sine wave starts to fourm
some where right after the 180 degree point then a biasvoltage on the ground wire can both advance and retard the spark by several degrees a good start would be about 5% of the charging coils peak voltage
i dunno but im gonna try it "also if it works then the bias voltage can be supplied by the lighting circut