QuestionI have worked on small engines before, and this one has me stumped.
Weedwacker...pp335, just over a year old, I live in California, and it is only used during the spring and once or twice in summer.
About the fifth time of use, the rpm's and power dropped off. It will start and go to a high idle, but full power will kill the motor.
what has been checked....
ignition coil....ok
spark plug not fouled, but turns black after short run (1. min)
clean gas tank
free flowing fuel lines
piston has been pulled, no scoring, ring is free, seals are fine
no carbon in the exhaust port
air filter clean
carb float valve was removed and checked for clog...none found
all carb linkages work smoothly
fuel pump works correctly
spark plug does show excessive fuel (turns black)
this motor does not have a reed valve...what is weird is it has two butterfly valves in the carb plus the third choke butterfly.
Choke works fine.
carb adjustments are ok....adjusting the idle and highspeed will cause is to die or run slower. Max rpm is about 3000, and the cutter head just starts to turn...the engine/cutter head is free.
If it wasn't still new, it would be in the garbage. I found out two late that it has a two year warranty, not one. My bad.
AnswerThe o-ring that seals the rear engine shroud to the engine case is prone to leaking. I apply Permetex N0. 2 non-hardening to the o-ring and rear engine case before assembling.
The other problem I have found a couple of times is a defective coil. Some coils use an internal transitor to control timing advance. A defective transistor inside the module is almost inpossible to trouble-shoot other than replacing the coil. This is very, very, rare...the last one I found was probably almost 15 years ago.
Try sealing the o-ring and see if it runs any better.
Eric
