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1988 Yamaha Big Bear - No Spark/Won't Start

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About 2 months ago I took drove my big bear from the garage and parked it in the shed, no problems. I started and ran great.

Today i tried to start it and it wouldn't fire. i pulled the plug and put it nxt to the cyinder and ther was no spark. I put a screwdriver in place of the plug, in case it was a bad plug, and same thing, nothing.

I checked the 30 amp fuse but no idea what to check next, or how to check it. I highly doubt it's the CDI box, or stator, I don't believe they would just die like that.

Any suggestions????

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my guess would be the stator given the age of bike and history of yamaha for that model. i was told the stators were not very good up until mid '90s .... but you could try and check everything else like coil, regulator and maybe cdi, but i'll put my money on the stator/pick up coil ....

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I'll get out my service manual and check it out. Didn't think those things would just die like that. Running one day, nothing the next.

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No I'm really confused.

I tore off the front plastics to check connections, still nothing.

Went out a couple days later to show a buddy who stopped by, and it started right up.

The next day I put the plastics back on but didn't have time to finish, it ran when I was done for the day.

The next day I finished putting it back together, and again it wouldn't start. I reached under the front plactics and giggled the wires and it started, I drove it around the yard and it died. I again giggled the wires and it started and ran, then it died and I haven't been able to get it running.

any suggestions? could it be a loose or broken wire, or could it still be the stator/pick-up.


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that sounds like just a broken wire. i would try to isolate the wires that you jiggle and try to narrow it down, harder than it seems i know. check for wear marks or kinked wires too ...

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Check the kill switch and the wire going from the kill switch to the terminal board. because it kills the spark to shut down the engine.

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Check the kill switch and the wire going from the kill switch to the terminal board. because it kills the spark to shut down the engine.

I see the wires coming from the kill switch, it goes to a 3 prong plug, from there I can't find where it goes. where is the terminal board located? if i pull that wire off the terminal board will that elimanate the kill switch from the equation?

how about this:

from what my wiring diagram shows the kill switch has a black & a Black/white wire. the black goes to ground the B/W goes to the cdi unit. Am I correct to assume the kill switch grounds out the system much the same as a lawnmower grounds out the spark plug to stop it?

If I were to cut the B/W wire where it comes from the kill switch would that eliminate the kill switch? I could always solder it back together.

Edited by toolman0114
more info added

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I pulled the front plastics off again and started giggling the wires one harness at a time, what I found was when I shook the leads going to the key switch it fired, then died. I shook it again and it started, briefly. The bottom plate on the key switch is held onto the main part by 3 locking tabs, the plastic was so dry and brittle that one tab was missing, and the main body was cracked. I pushed it together and hot glued it in place and it starts/runs great. I ordered a new key switch. Thanx for all the help and advice.

This is by far the most helpfull board on the internet.

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