Spark plugs are getting killed pretty fast

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Johnny - 19 Oct 2004 17:15 GMT

Hello all. I have recently purchased a 1980 Yamaha 650 Heritage Special
from a friend for a whopping $100.00. After doing so, I had to do some work
on it to get it up to speed. New handlebars, new cables(clutch, front
brake, ect.), new output shaft seal, a whole lot of cleaning up, and an
entire upper block rebuild (Head gasket was blown, so I figured I might as
well change all the gaskets). After doing all this, my spark plugs wore out
in a couple of weeks. I took it to a cycle shop in my area, and found that
after cleaning out my carbs, their sync was way off. So they hooked the
bike to their machine, and set the carbs to sync at 14cm, just like they're
supposed to. I bought more spark plugs, and it ran like a dream come true.
Then, about two weeks later, the spark plugs did the same thing. I'm
running out of ideas as to why this is happening. Any insite would be
greatly apprecieated.

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LittleJohn - 19 Oct 2004 18:27 GMT

> <snip> After doing all this, my spark plugs wore out
> in a couple of weeks.

Define "wore out". Covered with oil, rich mixture, burned, melted,
broken, what?

I've a feeling that if you find the meaning of "wore out", you'll also
find the cause of the problem.

LittleJohn
Madison, AL

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Johnny - 20 Oct 2004 05:07 GMT

Well, I suppose they're burned. They have a black solid substance on them
that does not appear to be oil. The actual structure of the plug looks the
same, so I wouldn't say they're broken or melted

> Hello all. I have recently purchased a 1980 Yamaha 650 Heritage Special
> from a friend for a whopping $100.00. After doing so, I had to do some work
[quoted text clipped - 9 lines]
> running out of ideas as to why this is happening. Any insite would be
> greatly apprecieated.

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LittleJohn - 20 Oct 2004 13:29 GMT

> Well, I suppose they're burned. They have a black solid substance on them
> that does not appear to be oil. The actual structure of the plug looks the
> same, so I wouldn't say they're broken or melted

You're running way too rich. As both carbs appear to have the same
problem, you probably made a mistake when you reassembled them. Take
then apart again and make sure you have the correct needle jets in the
correct seats. Either that or both floats are bad, which is possible. Use
a short length of clear neopreme tubing for a quick check of the fuel
level in the bowls. (Easy to do, just google for instructions if you don't
know how.)

Good luck.

LittleJohn
Madison, AL

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Tostada - 21 Oct 2004 04:49 GMT

> > Well, I suppose they're burned. They have a black solid substance on them
> > that does not appear to be oil. The actual structure of the plug looks the
[quoted text clipped - 7 lines]
> level in the bowls. (Easy to do, just google for instructions if you don't
> know how.)

And double-check that you have the right heat range plugs in the bike.
If they're too cold, they'll foul.

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Motorcycle Forum / General / Yamaha / October 2004

Spark plugs are getting killed pretty fast