1982 Yamaha Seca 750...me again... - Page 2

 

Older low voltage ignition systems only put out 10KV or 12KV.

Therefore, the spark plugs had to be gapped around .025 to .028.

The spark gap was so small that random molecules of a lean mixture
couldn't find the spark as easily as it could find a larger gap of,
say .035
to .040...

So carburetor idle jets had to be bigger than optimum, and then, in
the
1980's, the EPA demanded very lean idle mixtures to pass exhaust
emissions tests.

So the cold starting problem became even worse.

If the engine starts easier with the spark plugs gapped around .022,
that tends to indicate lean idle mixture.

 

There's carb rebuilds and there's carb rebuilds.  If the fuel was not run
out of the carbs when the bike was parked (the best way is to run
the bike until the gas tank is empty) then the carbs would have been good
and varnished up.  If your man simply gave the carbs a quick once through
and
replaced all the rubber parts, he very likely didn't get all of the carb
passages cleaned out.

If the passages ARE passing fuel, then all that is really needed is to
ride the thing.  All modern gasoline contains detergent (it's federally
mandated) and after 3 months of riding it every day any varnish in
the passages will have been cleaned out by the detergent in the
gas.  You can also hasten the process with Berryman's B-12 chemtool
in the gasoline or Seafoam, or even Chevron Techron.

If, however, some of the small passages where solidly plugged,
then the only way is to soak the carbs, then blow out the passages
with compressed air, then soak them again, then blow out the
passages again, and repeat this process until the passages are
cleared out.  If that does not help then you have to poke small
wires through the passages, but you really need to be very
familiar with the carb before doing that.

What was the condition of the inside of the gas tank?  Was there
-any- visible rust?

Ted