04 YZ 250 2 STROKE ISSUE)

Ok guys i started a new thread on this because i found something out..
It turns out my brand new spark plug was not producing any spark at
all.. as soon as i used a different plug the motor started right up..
this is the second plug i have burned through in a week.. would anyone
know what might cause me to kill these plugs.. I am running a 32:1 mix
of yamalub with a pc pipe.. rest is all stock..

seems weird that my bike would kill two plugs in one week..

THANKS FOR EVERY0ONES HELP SO FAR..

 

I had a lot of trouble many years ago with the plugs on my new RD350,
they kept oiling and just stopped working after a few miles with no
spark, like yours. I put hotter plugs in which cured the problem,
although they tended to be too hot for high-speed running. I ended up
using two sets of plugs, one pair for town use and another for fast
riding.

Leon

 

You might have a loose connection in the wiring from your CDI unit to
the ignition coil, so check out the wiring harness and the connectors.

The CDI unit is probably supposed to get a lot higher voltage than it
would get from a 12 volt battery. You'll have to do some research to
find out what this higher voltage is, but CDI's often use about 100
volts from the generator.

Try to find out what the resistance reading of your generator's stator
coil should be
and carefully measure the resistance with an ohmmeter.

Hopefully the ohmmeter will have the ability to zero out the resistance
of the test leads so you can get a true reading.

A low resistance reading indicates shorted windings in the generator
stator so it can't produce the required voltage.

 

So this brand new plug worked for a while, then quit, or did it just
never work at all? Sometimes you get a bad plug. If you kill your new
(no, not that new one, the new new one!) plug, then you've got a problem
somewhere. If the problem is fouling, Leon's suggestion seems reasonable
to me.

[snip]

--
Later,
John



'indiana' is a 'nolnn' and 'hoosier' is a 'solkk'. Indiana doesn't solkk.

 

My Japanese motorbike experience goes back to 1963, and I experienced
the situation Leon describes. But I didn't know how important it was to
change back to the colder plugs after warming up on hot plugs until I
burned holes in a few pistons.

When the plugs get too hot, it doesn't matter what the ignition timing
is. The spark plug ground electrodes glow cherry red or even orange,
and they cause the mixture to preignite *before* the spark occurs.

Preignition sounds like loose valves. There's an annoying tinkling
sound in the engine, and then maybe you start hearing clattering and
banging as the mixture detonates.

My first two-stroke motorbike was a 1961 Yamaha YDS-1 twin that
somebody had converted to flat tracking. It had no brakes and the rules
only allowed 4 speeds in the transmission, so the previous owner had
brazed a stopper to the shifter drum.

And he'd removed the kick starter to reduce the weight. I had a lot of
work to do to get that machine onto the street...

 

I tried shot-blasting the plugs on the Ariel Sport Arrow I once had,
but the lead deposited on the insulator stopped them working. 8-(

Leon

 

I once sentimentally bought a pair of 15 yr old YDS-1's surplus. both
seized up. I spent an entire winter POUNDING & POUNDING on those stupid
cylinders/pistons trying to get them free. Eventually gave up, and
hauled them back to the place I found them..... I also had a perfect
Daytona (RD400) so the sentiment wasn't wasted too much on the old
twins.....

ca

 

I'd have probably tried to find someone with a milling machine and got
them to mill large holes in the pistons. They could then be broken up
into smaller chunks and got out that way. I'd love to have a YDS-1, I
still have fond memories of the little YAS1 I bought new in 1969.

Leon