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Big Al

1987 Yamaha Big Bear How To Test CDI

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Hello. I'm new to this forum. I just bought this big bear. This thing is show room condition. Now I haven't had time to dig into it so it might be easy to fix. But the guy I bought it from said it needs a CDI box. Now is there away to test these to see if it's bad? I see they are hard to find. Any recommendations on batteries? Any help would be greatly appreciated. I'll get back with results one I get time to look at it.

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That is in amazing condition! Great find! Im not sure on how to test the cdi box but first i would put a new battery in if the old one is bad or missing. Measure the dimensions of the battery compartment to find out what size you need.

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Well I tore it down and tried jumping it. It turned over for a second and then some buzzing/clicking came from the rear and briefly from the front. I would hate to by that CDI box not knowing if that's the problem. I see some relays in the rear. Just wondering the next steps to getting this thing running?

 

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Well I tore it down and tried jumping it. It turned over for a second and then some buzzing/clicking came from the rear and briefly from the front. I would hate to by that CDI box not knowing if that's the problem. I see some relays in the rear. Just wondering the next steps to getting this thing running?

 

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Topic moved to Yamaha ATV forum and added issue/question to topic title 😀

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Yes it's coming from the solenoid. So with that said the CDI should be ok being there is power to the solenoid?

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Not necessarily, although that is not completely ruled out. What could be your issue is a lack of a full charge-12 volts or so- to everywhere it needs to go. If the solenoid is buzzing then there is something causing less power from getting through. Make sure your battery connections and other connections are tight and that all your grounds are good too. If a ground is corroded then sand it and see if that helps. Hope this helps.

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Yeah, get an extra set of hands to help and test voltage at the starter. I hope you get it figured out, I have a 2000 Big Bear I'm tearing down and trying to sort out. You know the old "it ran when I parked it" routine LOL

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You must have at least 12 volts, does the battery look old?? If it's old it might not jump at all.

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I just had this starting problem. The hot wire on the starter stud was deteriorated to rust powder. I replaced the starter and it cranks easily now. I too now have no spark. I am not saying the two are connected in any way. Just trying to help and learn...

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Most of these bigger quad engines require a full 12 volts or at least a charge close to it, in order to power the ignition system. Weak battery/charge = weak or no spark most times

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Wasn't there a post a few years ago on a quick ignition test with an AA battery?

Saw it once, but cant find it now...

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Hi there, I’ve got a 1990 Big Bear 350cc and was having trouble getting it going. I tried just about everything. I even bought a CDI unit. Well it turned out to be a faulty carburetor. I bought a single cable one and it works great. So…I’ve got an extra CDI unit that I’d like to sell. $150 Canadian + shipping 

I’ve also got a completely rebuilt dual cable carburetor that cost me $495 ca. I’d sell it for $300 Canadian 

( [email protected] )

I live in BC

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Wasn't there a post a few years ago on a quick ignition test with an AA battery?
Saw it once, but cant find it now...

If someone could find the link to this i would like to check it out. Sounds very interesting.

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If your Yamaha is cranking over fine but hasn't got spark, it's usually the stator. CDI modules rarely fail.

There are tests you can do with a multi meter on a stator but not on the module usually.

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Hi, I’ve also found bad connections in the spark plug housing. Reach in there with a slot head screw driver and unscrew it and check it out. 

Just sayin’ 

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On 9/5/2018 at 3:56 PM, bryanta0502 said:


If someone could find the link to this i would like to check it out. Sounds very interesting.

Any update on this? I'd be interested too.

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Wow. Everyone is all over the place on this. 

Great looking bike awesome find lucky you! 

The cdi is a working or non working component.  So the fact that it fires up I would say it’s good.  

Now since you have all the plastics off and everything is exposed I would take your time and unplug each plug one at a time and clean and add electrical lube and reconnect. 

A good eye glass screwdriver allows you to get in and scrape clean the contacts of all the plugs.

after that go through all the wires that are attached with a bolt or screw, grounds, battery connectors and the starter relay .  It’s very possbale that the starter relay is no good and a much cheaper part to replace. Keep in mind the electrical system is big! That means the coil wires, ignition, handlebar controls, regulator etc. do it in sections and move on to the next section.

After all this is done if it still does the same thing it hasn’t cost a penny before you start guessing and buying parts and all bad connections are ruled out. 

Put a fresh battery in that baby and see what you got.

Lastly is I’ve had a bad cdi box and one way that it will not perform is if it has moisture inside. Simple stupid way to get that out is to put it in the oven for 10 min on 250! Make sure the oven is on 250 before you put it in and no more then 10 min. Take it out and cool off and try it. 

Good luck and keep up posted.

 

 

 

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