Ignition replacement...Dont laugh!

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Old 04-04-10, 04:09 PM
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Ignition replacement...Dont laugh!

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Ignition fitment project...Dont laugh
by bobbyg Sat Apr 03, 2010 8:35 pm

Okay guys, I have an odd request of information, but first Ill tell my story. And, Yes, this is for real.

What it is: I have a 1983 Husqvarna 250XC. No, it's not a piece of Husqvarna lawn equipment; It's a dirtbike.

It originally had a magneto on it for the igntion system. Basically just a stator that is mounted to the engine case, the crank comes up through the middle and a 'mushroom shaped' flywheel spins over the top of the stator which are both lined with either magnets (the flyhweel) or coils (the stator).

What Happend: Unfortunately, the end of the crank that is tapered and threaded that holds the flywheel on broke. The retaining nut broke off and the flywheel cracked too. I had to cut the flywheel off the crank because it wedged itself on to the tapered part. While cutting it off with an air grinder, I cut the stator to pieces too since it was RIGHT under the flywheel. I also had to cut the damaged end of the crank off which in the end left me with a crank that is overall about 1.5 inches shorter.

What I Did: To get it running again, I racked my brain for ideas. My first and initial idea was awesome, and a partial success except for a few problems which ill mention later. I thought about using HEI ignition off of an early 80's General Motors car or truck. being that I work for an autoparts store, I have access to tons of literature and illustrated guides. I cobbled up an ignition system with a pickup, crank trigger, coil and ignition module, and (unfortunately) a battery. I had to drill and tap a hole in the end of the crank to install a small piece of metal to trigger my magnetic pickup in relation to piston TDC.

Problems: I have no markings to go on to set ignition timing. That was all set by a keyway in the crank/flywheel, and holes in the flywheel and stator that you line up. It's all just a rough guess-timate by feeling down the plug hole for TDC and setting accordingly. Second problem is that you need to have an onboard battery that is constantly discharging. A) I dont have room for one, so I strapped it under the back fender. B) This bike has head and tail lights on it that need to run too, which i didnt wire up since that would compound my problem.

Well, I ended up getting it running. However the timing is sketchy; either too much retard or too much advance, cant ever get it right. It will almost kill your leg with the kickback when you try to start it, so you retard the timing a tiny bit about the width of a flathead screwdriver blade (thickness of it rather) and it will barely idle but has intense top end.

My Idea: I have been looking for other batteryless ignition systems, but none seem to be anything I could fit on my crank. Here's a picture of my crank with my 'pointer' (trigger) and my pickup wired into the ignition module.



I have looked in my books at work for lawnmower and power equipment parts and found this.

Ignition Module Universal, 7-01749, 33-053, 29-1089, 7-01752, 98219, 440-065, 8786, 31-8786, (Universal); Fits most 2-cycle & 4-cycle engines. on sale from Tulsa Engine Warehouse

However Im not sure how I would wire that up or even use it. It says not for use with battery ignitions in the description. Also, I realize that I couldnt run my lights off that system, which isnt THAT big of a deal but getting the thing running is more important. Do any of you know of any other solutions I may not have seen or been made aware of? I would appreciate ANY help. ThanksT
 
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Old 04-04-10, 04:31 PM
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I've seen a lot of people spend a lot of time trying to make something work without spending the money to fix it properly... This is why I won't work on bikes anymore... I suggest fixing it properly & it'll work properly... If you'r time is worth nothing or you have nothing else to do, than it's an experiment.. Remember the spark advance curve is totally different on these bike engines than on old 305 Chevy... You'll never get it right using auto parts... Just my thoughts from past experience... Roger
 
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Old 04-04-10, 05:52 PM
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That universal setup is just to replace points/condenser. The coil you had from the auto application had a battery fed coil.

What were your plans on the universal job for a coil?
 
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Old 04-04-10, 06:59 PM
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Hopkinsr2: There is no timing curve with the stock ignition on this bike. It stays a static 20 degrees advance. There's no curve in the setup I have now either since there is no vacuum advance or weight curve mechanisms. The theory actually works, just finding TDC with the hall effect trigger is the hard part since its trial and error. I know people with 4 wheelers who have put HEI on them, which is what made me think of applying it to my bike, however a 4wheeler ATV also has a battery compartment. My bike does not. This is just a side project so it's nothing that will make or break me. Today I dug around my shop and found a flywheel magneto and coil from a weedeater. I chucked the flywheel into an electric drill and spun it past the coil which I bolted to a holder rod. It sparks great, and I believe I could adapt that to the husky. I wouldnt really have any tail light or head light but thats no big deal really.

marbobj, you say that that universal setup replaces points/condensor setups. Are you saying that kit is basically just a pickup coil?
 
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Old 04-04-10, 07:10 PM
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Not exactly - a pickup coil is signal. That thing would have a capacitor or something like it. Just reading the rest of your post.....

If you're doing the thing with the weedeater, I imagine that is an electronic ignition module = coil/built in capacitor=CDI. If you can get that rigged up it'll do the ignition for you with nothing else.
 
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