I have had a YT5700 since new. I am guessing its an early one since the serial number is 000263.
It has been a great mower but it now seems to be only running on one cylinder at times. It is an
intermittent problem and comes and goes. I know that the fuel pump is pumping fuel and I just took
the carburetor apart and cleaned it. All seems well with the fuel system. I thought I had the problem
isolated to the coil but after replacing that the problem is still there. Every time I pull the plugs and
check them I have spark on both plugs. I am fairly sure it is an electrical problem as I can smell the
un-burned fuel coming out the exhaust when it is acting up. Any advice on what to try next?
It goes from running like new to running on one cylinder and then back again like flipping a switch.
Sometimes runs for days perfectly. I replaced the coil but did not yet replace the spark plug wires and
caps. Will try that next I guess. Carb is clean and looks perfect but I did not yet replace all the fuel
lines yet they are still original but look fine.
I replaced one of the coils after catching that one testing for spark and not seeing it. I guess it is also possible that
the other coil has now gone bad as well but is intermittent and have not caught it yet. The first coil was very hard to
find and very expensive so if that is the problem finding another one may be an issue.
Thanks for the advice. I will change out the fuel filter and check the valves. Had the problem again
yesterday and pulled the plugs only to see spark on both sides. Spark was a bit weaker on the side
with the new coil which is odd. After sitting overnight it started and ran perfectly today. I am thinking
it is not the coils at this point but rather a loose wire someplace.
Any advice on how to clean the carburetor without removing it? I mean it surges like crazy and I am not about to take the carb off myself. Are there any additives I can spray at the air intake or add to the gas you might recommend?
Seafoam is probably one of the better gas additives to add, so try that first.
Any basic carb cleaning spray around the linkages to the carb also help.
Surging can be fuel delivery, air leak or governor troubles.
Make sure the gas cap air vent is clean and open and air filter is clean too.
OK ty for the advice I will give it a try I never would have thought of the gas cap vent so I can pull the cap to check quite easily. I was able to fix a surging problem in a brand new Tecumseh engine by cleaning one of the tiny jets. The carb on these Yamaha's look somewhat more or a challenge.