Motorcycle Forum / General / Yamaha / April 2007

Hi,

I need some expert help with my `82 Yamaha XS650J Maxim.

Problem:  Won't start when cold.  When you try to start it, at any choke
(bypass) setting, it will fire for one second, and then won't fire again.
If you give it a little starting fluid in the air box, it will start.  Once
warm and running, runs fine.  I've put several hundred miles on it, just
won't start cold.

I have cleaned the carbs three times.  Please read the list below of what I
have already done carefully.  I would appreciate any help.

I have done the following:

-    Thoroughly dismantled and cleaned the carbs three times.
-    I borrowed a different set of carbs from a friend who has an `81 650.  I
cleaned them for him (part of the deal), and put them on my bike, and then
it started and ran great, perfect.  Because of this, I am pretty confident
it is a carb problem.
-    As near as I could tell, his carbs were identical to mine (jets, etc.) and
had the same model number on the bottom of the carb bowls (both were
Hitachi).
-    The model number on the bottom of the carb bowls of my carbs matches the
model number of my bike (5N8).
-    When I clean my carbs, I take them completely apart, except for the pilot
screw set (as described on the XJ CD set, see below).  Each time I soaked
the carb body in part cleaner for 12 hours.  Blew compressed air through all
passages, replaced pilot and main jets with new jets (first time only).
I've paid special attention to the bypass valve and passages.  The inside of
the carbs are spotless.
-    I can't seem to get the pilot screw set out.  I've tried toothpicks, a
jeweler's screwdriver, and compressed air, but can't get it out.  Any
suggestions???  Do these parts screw out, or is it just held in by the
o-ring?  The “pilot screw set” consists of a washer, spring, and o-ring,
correct?  If these were dirty, would they cause the problem as I described?
-    Checked for air leaks by spraying starter fluid around the intake
manifolds and boots (did not increase idle).
-    Replaced the air filter.
-    I have the original owners manual, service manual, and XJ CD set, and have
researched them thoroughly.
-    I've checked the float level.
-    I've checked the tank for rust, removed the rust, etched and coated it.
-    Installed a fuel filter.
-    Replaced the fuel line.
-    Checked the fuel petcock.
-    Fuel mixture screws are factory set (still had the red silicone over them
when I acquired the bike).  I don't own a Colortune, so I have not messed
with them.
-    Had it at the local bike shop, they gave it back to me, unfixed, after 5
weeks.
-    The local bike shop checked the compression and said it was 120, 120, 130,
140.
-    Posted here before, got lots of feedback about fuel additives.  Tried two.
Ran through a tankful.  Also (per previous post) tried getting up to about
60 MPH, pulling in the clutch, dropping it down 2-3 gears, opening the choke
wide open, and popped the clutch (to create vacuum and suck any debris out
of the bypass valve openings.  …I don't think fuel additives are the
solution here.
-    Replaced the spark plugs, changed the oil.  J

I traded some antiques for this bike and have to get it running, or will
listen to “I told ya so” for the rest of my life.  J