STIHL FS100 4stroke not starting - help

[blazer]

I have had the Stihl FS100 for say 8 yrs mostly starting ok but now it really is a problem to start. I often have to dry out say x3 plugs and am lucky if using x3 dry plugs it will start. Mostly it will splut once per pull for a few times before the plug wets itself. If it does start it will run well but not start from cold next time. I have done all the normal checks, stripped and cleaned the carb, reset the ignition close to the flywheel.

 

Rare for me to be beaten by a put-put but this time I'm close to giving up.

[fodenwagon]

Have the compression tested,might need a new Ring.

[Maico490]

As no one else has chipped in. First off I'm no expert on the 4-Mixes but have picked up a few things on other forums. It sounds like it is flooding so check that the metering needle isn't leaking. Should hold 5psi on the inlet pipe. Don't over do the pressure though. The valve clearances need checking every 100hrs or so and the early ones had issues. Also there were problems with the ignitions. From memory they still spark but fail to full advance and are hard to start. They have a lifetime warranty to the original owner in the US but not sure over here. Hope this is some help.

[blazer]

Thanks for the tips, it got harder to start than near impossible. When we first brought it we had flooding/smoking problems but seamed to adjust it out. I checked the valve clearance ok.

 

But suspected the ignition module. I had a simular ign unit fail on my MS280, the resistance on the faulty 280 unit on hte LT side was +2 M ohms both ways and the FS100 as 4M ohms the new MS280 unit was 1.8Kohms both ways, so have put one on order, but will take a couple of weeks via the local supplier.

As the LT side is an encapsulated electronic unit a simple DVM resistance test gives a good indication.

 

Its always a bit of a problem with engine faults as the more you touch the more could be wrong by putting faults into the system. I stripped and cleaned the carb and tried new plugs + hot plugs but still took say x3 plugs to fire up, then it would run fine but not restart.