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2000 Yamaha Big Bear 400 No Spark

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Still working on the 2000 Big Bear with a no spark issue. A lot of this has been covered in an older thread, but I will summarize.

Bought it with the previous owner telling me it needed a new wiring harness, but the wiring harness was in tact and seemed to be fine, except starter solenoid and coil was missing, also the engine was stuck, and no spark plug. Got the engine free and rotating, checked compression, it was 130, not great, but good enough to run. Hooked up a battery, nothing , went through all the wiring and found starter cutout relay bad, replaced that, now I have it rotating with starter. Pulled the plug checked, no spark. Checked start/stop switch, working like it should, reverse relay was bad ,replaced that. Checked continuity from coil to CDI, good, checked pickup coil resistance, within specs, checked anti kickback coil resistance, within specs. What am I missing.

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Tiny flake of rust or metal bridging between the trigger coils iron core, and the flywheel magnets.. That is enough.. One single tiny slither or steel..

Or there's still something not right with the combination of cdi, stator, switches, loom... something the previous owner had changed before deciding it must be the wiring loom.

You could check for a flicker of AC from the trigger..  No guarantee it will mean anything if there isn't one, because not all triggers put out power, some change their resistance instead, but if it does pulse it means  it is not magnetically shorted.

Edited by Mech
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Thats a good thought, i may do that just for fun, no telling what they would charge to do that, but nobody around here brings this old stuff to a dealer, they charge more to fix them than the bike is worth, that's why you see so many junked ones. Example: I have a 2003 Cadillac it was my mothers car, pristene condition 45,000 miles on it,  took it to the dealer, they did not even want to work on it , said the car is older than most of their mechanics, this certainly isn't the world I grew up in ,changing daily. 

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Amen  to that Brother.. 

The dealers know what we are all up against with these electronic bits. They are in the same boat, once they have eliminated everything else, the computer is the suspect, but nobody has a machine to test them so we have to try a substitute to confirm it.  I used to have a working relationship with the local car wrecker and he used to let me borrow car computers to try. Can't hurt to talk to the bike shop..  they might have some insights if nothing else..

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Got out this afternoon and did a few tests, made some test leads to fit into the CDI plug of the wiring harness, got the mechanical meter with needle, hooked it up to the white/green and white/ red for the pickup coil, set on the lowest AC voltage setting which was 15 turned over the engine and got nothing, thought, this isn't working at all, then I moved my leads to the rotation direction coil wires white/blue and red rotated it over and the needle moved. So it does work, thanks you for that info Mech. So I have something wrong with the pickup coil even though it had the right resistance rating of 528. Next step is pull the side cover and see what's going on with the aftermarket stator. The wires are not color coded the same as the OEM wiring harness wires, im going to look inside and see what goes where. Any thoughts are greatly appreciated.

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Nothing I haven't mentioned before I don't think.. Check the little metal tag is still on the outside of the rotor, and look for any tiny flakes of metal bridging the gap. The flakes of metal often lay down flat till the trigger plate gets close, then they stand up and bridge the gap.. It only takes one flake to stop them working. Oh, and the gap ..  check the gap is right, though a wrong gap will normally still fire the trigger coil into life.

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Actually Gw..  First up, use the analogue gauge on ohms and see if it changes resistance momentarily as the crank turns.  It might be that that's how it works and triggers the cdi..  Digital gauges don't pick up very brief changes..  not unless they are very good ones.

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Bugger..  It was a long shot anyway Gw..  Just in case it was a more modern sort, which to be honest aren't real common on pre-EFI systems.

If it's easy enough to take the side case off then that's probably the next thing to do.. check the mechanical bits.

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Ok..  A flake of rust could be the problem..

Is the metal tab still on the outside of the rotor/flywheel ? The one that fires the trigger coil..

Interesting that that stator doesn't look like the ones in the book with the extra large "kick-back coil/winding".. 

That's not green corrosion down where the wires go into the trigger coil is it ?

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Thanks for the reply Eugen, im not sure, I have not had one of these apart before and that was my first thought when I saw it, appears it should be in the recessed area looks like it belongs there I am going to take some measurements and see where it lines up with the magnet on the rotor, the other way around. 

Mech my magnet is it tact looks fine, I am going to inspect it closer when I clean the rust off.

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