Why would a motorcycle CDI unit Blow??

gline · 12-05-2005 10:56am #1

Just wondering what would cause a cdi unit on a motorcycle to bow or melt??? Its a 1988 vtr 250. Its not my bike but i was just curious as to what could cause that? obviously there is a more erious underlying fault or can that happen just over time???

Elfish · 12-05-2005 11:40am

Sometimes it is just pure vibration. They appear to be bust but if you saw it open and look at the solder joints, you might notice one joint that is not in good condition. I had this problem, and I sawed open the hard casing and soldered a good number of the joints. It worked and saved a good few quid! Often times though, I think that ignition problems are blamed on the CDI, when in reality the problem can be elsewhere (even if the other problem is hard to find in itself, people tend to blame the CDI......)

Dunno why they would blow outside of the above?

gline · 12-05-2005 11:43am

i think this one is genuinely melted (literally)

echomadman · 12-05-2005 12:15pm

check that the regulator is working before fitting a new one, if it melted it's likely it got a massive current or voltage spike although on a bike that old some critical component may have simply failed, and caused a short or over current situation in the CDI curcuit.

Elfish · 12-05-2005 12:43pm

echomadman wrote:

check that the regulator is working before fitting a new one, if it melted it's likely it got a massive current or voltage spike although on a bike that old some critical component may have simply failed, and caused a short or over current situation in the CDI curcuit.

Yeah, but if the regulator is gone, then I think he would have gotten a blown main fuse rather than a burnt CDI. The real question is what would cause the massive current or voltage spike that you are talking about? (Please don't anyone say the engine spark leaking back to CDI!)

One other thing to check on your CDI is the terminals(and where they are plugging into - any green/rusty stuff on either end then clear it off). Check engine earth too - CDI is dependant on it as well.

Still doesn't why the CDI blew, but if you have a broken one and you get it fixed do you really give a f**k for how it blew in the first place?

gline · 12-05-2005 12:51pm

Elfish wrote:

Still doesn't why the CDI blew, but if you have a broken one and you get it fixed do you really give a f**k for how it blew in the first place?

no.. but what id be worried about is replacing the CDI and the newer one blowing too, that would be a waste of money and problem still not fixed

Elfish · 12-05-2005 2:10pm

Good point. So what causes the CDI to blow? *waits for can of worms*

gline · 12-05-2005 2:20pm

Elfish wrote:

*waits for can of worms*

thats what i am thinking

Why would a motorcycle CDI unit Blow??

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