I have a Homolite ST 145 String Trimmer. When starting warm it kicks back like the timing is advanced. The ignition module is tight and has never been moved. Can Tolerances change on module component and cause the timing to change? Can I relocate the module and retard the timing.

Thanks,


John

Hi,
The module has an integral ignition advance system(per EPA regs) and cannot be adjusted. Flywheel is keyed though that is seldom the problem on that brand.
Peace,
Clarke

HI,

I checked the flywheel key just to make sure. It's OK. What do you think of this scenario. Either the components in the module that advance the timing have failed and the spark is permanently advanced or the octane of the fuel that I recently purchased has a lower octane and is causing pre-ignition.

Thanks,

John

Hi,
Pre-ignition is unlikely. Best to always use fresh, mid-grade fuel with a quality oil.
Try removing plug, inverting the engine and seeing if there is liquid accumulation in the engine by pulling it over to expel it through the spark plug hole.
There is also a "very" small hole in the top of the piston to reduce compression during cranking. It is laser drilled and the chance of finding a wire small enough to try to clear it is virtually nonexistent. Getting the engine to crank with known good fuel and bringing it up to operating temperature will often clear it.
Spark advance problem will make the machine virtually uncrankable or have no performance, since it is a governor function and will change by RPM's.
Peace,
Clarke

Hi,

I tried drying it out. I even blew compressed air for awhile. Didn't help. In fact if I flood it a little it won't kick back.

I just tried it again. Cold OK. Hot kick back. Pull plug wire off no Kick back.

I'm using low octane fuel, But I always have. The next time I get out I will get a gallon of mid range fuel and try that.

Thanks