Motorcycle Repair: Carb issues, rubber diaphragms, vacuum leaks

Question
I have a 98 vs800 i am having a few issues but i think all related.I have fule comming out of main air jet sometimes on the no 1 carb.Also the no 1 cylinder is not firing all the time.and i cant keep the bike running.I was having a prob with the 2nd cylinder dead and cutting out-took it to a shop and paid the guy.When i got it back the no 2 cylinder is working great but the no is not.I went thru the carb and cleaded it,pulled plugs and cleaned.Wich i paid for new plugs and didn't recieve.Now the guy wont be back in town until Monday and bike week started today.I was hoping to go this weekend on my bike.Any help would be greatly appreiachated

Answer
Hi Scott,

If the problem is the carb then you can only
double check all the passageways, jets and
float needle/valve and float/fuel level.
The float needle valve must not leak when the
float is raised.

There is also rubber diaphragms on some
carbs, one under a small cover on the
side of the carb and the main diagragm
under the top cover cap.
These must not have any pinholes in them.

The fuel supply must also be checked.
This might include checking fuel flow
from the fuel pump.

Where the carb attaches to the engine
there must not be any air or vacuum leaks.
Check around the carb with wd40 or carb cleaner
spray. If the engine speed changes then you have
an air leak.

Check your spark plug to see if it is wet or dry.
Wet means it's flooding or misfiring and dry
means insufficient fuel.

If you suspect the spark you can try switching
the two ignition coils to see if the misfire
changes sides.

If you have insufficient valve clearance
the cylinder may not idle well as compression
will be reduced.

If the cylinder compression is low that cylinder
may misfire or not run well.
Compression should be minimum of 130 psi.
More is better.

You need fuel and a tight,clean carb, good compression and
a steady spark to make it run.
Try to isolate the problem to one thing and then work
on that.

Carb may need a new float needle/valve or
have a plugged idle passageway. Yamaha makes very good carb cleaner
that you could soak the carb in or fill the float bowl and
let it sit a few hours. That might help.

Seafoam is a good fuel additive to keep the system clean overall.

Good luck!
Wayne S.
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