Re: `82 Yamaha XJ650 Won't Start But Runs Great NEED ADVICE

 

Thanks to everyone that posted useful advice and tips.

I've tried the Berryman's B12 with no effect.  I thought it ran a little
rough at first, but I'm not sure.  I had also tried “Seafoam” carb cleaner
in a previous tank of fuel.

I've cleaned the carbs twice, very thoroughly.  Off the bike, all
disasembled.  All new pilot and main jets were installed.  Soaked the body
overnight in parts cleaner.  Blew compressed air through all the passages.
I even used an ultrasonic electric toothbrush to clean all the parts.  They
almost look like new inside.  Because of this, I doubt a blocked idle
mixture circuit. The carbs are very clean.  I used the OEM Yamaha manual
when replacing the jets, so I don't think I have them reversed.

I tried the, “go 45MPH, put it is first gear, and pop the clutch…”
suggestion also.

I don't think it is a battery, because my battery is new and I've been
keeping it charged.  Usually leave my charger on while cranking it and
trying to get it started.  It's only a 6 amp, but helps.  Granted, I've been
doing a lot of cranking, but I charge it up after working on the bike.

I did notice that once it is good and hot (like after a 40 mile ride) it
will idle pretty high, around 1300 - 1400 RPM.  The idle screw only takes it
down so far, then seems to have no effect.

In response to the mixture screw posting - I am a newbie but not an idiot.
I could learn to set the idle mixture screws but the screws on my carbs are
at their original settings and still sealed with the red silicone.  I would
prefer to get it running stock as is.

Could the symptoms be caused by float levels off?  I don't think so, but it
is one thing I have not checked.  Two of the fload drain screws are stripped
and I can't get them out.  Any suggestions for getting the stripped screws
out?

Otherwise, I'm still looking for suggestions to the original problem - won't
start when cold (sits overnight).  …Otherwise it runs pretty well and will
start OK, even after sitting for an hour or two.

Also does anyone know what size the main air jet and pilot air jet should
be?  I'm also wondering if mine have been changed at some time.  My OEM
service manual doesn't state the air jet sizes, just the fuel jet sizes.  My
air jets are 205's and 50's.

In regards to the poster that suggested measuring the voltage off the coil,
is that accurate?  I've heard of checking the resistance (OEM manual has
specs for resistance), but the voltage would be very high, correct?

Thanks again for everyone that posting meaningful advice.

 

kylentz@excite.com wrote:

I don't believe that there's any such thing.  If you're talking about
Sonicare, they don't have anything more to do with ultrasound than an
ordinary toothbrush does.  _Sonic_, not ultrasonic.  That means they make
sound.

 

wrote:


sounds like an airleak somewhere. are the rubbers from the
carb to the maifold tested? even a smal leak could do it.
i'm guessing you checked the slide diaphrams and they are
air tight?
try the smoke test, see if an air is blowing anywhere around
the carbs when you crank.
obvious also, but the starter is up to full crank revs?
will it kick start? bump start?
man, it's something subtly simple, i bet.
let us know your progress, ok?

 



This is an easy thing to test.

First get it started and running without the enrichment circuit. Next spray
the boots with a non-flammable aerosol such as WD-40 with the airbox in
place. If you spray a boot and the idle speed increases, you have located an
intake leak. If not, I would check for proper float height next.

Thirdly if the problem persists, check the valve clearances. Cold valves may
not seal tightly enough if the clearances are too tight.As the bike warms up
the aluminum head expands further than the steel valves resulting in
slightly more clearance which may allow the valves to seat better. At
cranking speeds even one leaking intake valve may affect cold start
performance.

 

On Thu, 17 Aug 2006 00:43:58 GMT, kylentz@excite.com wrote:


You measure the voltage on the primary side of the coil, not the
actual spark voltage.

--
RoRo