Hey guys. Im a huge GM fan and I have been working on a side project for the past couple months now. I had no idea where to ask my question so I figured this place looked good.
I have a 1983 Husqvarna 250cc dirtbike. (I can hear the laughing already). The flywheel/magneto ignition seized itself on to the crank and in order to remove that assembly I had to cut the end of the crankshaft. I was left with a crank stub and that is it. At this point buying a new flywheel/magneto wouldnt fix it due to the crank being too short. I had to search for other alternative ignition sources.
One morning I had an idea hit me: HEI ignition triggered by a hall effect sensor. Being that I work at an autoparts store, I went to work and leafed through the illustrated ignition guides writing down part numbers of pickups and reluctors I figured would work. In the end I found a pickup which fit nicely inside the housing on the bike and I ended up fabricating a triangle shaped arrow pickup which i screwed in to the end of the crank which was drilled and tapped
After wiring this all in to a 4 pin HEI Module and wiring everything to a small 12 volt power sport battery, i was ready...Or was I?
TIMING was one thing that stumped me. I physically looked in the exhaust port to see when the piston was up, and marked that point with a marker both on the crank and on the engine housing. Then I moved my pickup trigger to be dead on with the pickup however two things became my barriers:
1) The pickup does not sense the pointer when it is dead on, it sense it about 1/8 inch before they are parallel.
2) A degree is so small that when i move the pointer even a smidge, the bike has totally different behavior, whether it be intense low end and breaking up in the top end and almost taking your foot off while kickstarting (too much retard), or not even wanting to fire up/idle but having a major top end. (too much advance)
I have put a timing light on to try and see where my marks are lining up, and while i can see it, i dont have any numbers which I can correlate to my setup.
My question is this: If I buy a better timing light (as in one with a digital advance readout and so forth) will i be able to get a reading of the timing that I *CURRENTLY* have? Keep in mind I dont have a timing tab, only that rotating crank pointer/trigger. Do I have any options rather than a trial and error method?
Ive also heard of an HEI module used in some 1980 model Oldsmobiles with a 5th pin, which, when grounded reduces timing by X degrees (cant remember the number off hand). It was used to reduce strain on the starters back in the day. Im not sure using that would be of any benefit to me, just throwing that out there.
I appreciate any help! Here are a couple videos of the bike running. As I quickly found out behavior of the engine changes with load on it so after adjusting the trigger each time, there was no substitute for a test ride.