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finally found fix for throttle cable on FS450K

Started by Tom King, July 15, 2016, 06:40:51 PM

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Tom King

I couldn't figure out which forum to put it in.  It's a Clearing Saw (think monster string trimmer that runs a circular saw blade), not a chainsaw.

I bought it new for a job in 1999.  It got used occasionally, but the throttle cable kept breaking.  I could never figure out why the cable didn't last long because there is probably less than a 1/2 ounce for full pull on the carb linkage.

Some years ago, Stihl stopped selling replacement cables.  The dealer couldn't help, but did call and let me talk to a rep at Stihl.  He said the assembly from the handle to, and including the carb had been changed.

I cobbled up something that worked for a short while, but when that broke it sat for years.

Just browsing ebay last week, I found a new old stock cable.  I ordered that.  I also found a handle grip with throttle cable attached and ordered that.  I figured between the two, I might be able to rig up something that would work.

The NOS cable was the right one.  When I was inside the grip putting the new end onto the trigger, it was odd that there was such a weird layout for the springs for the trigger and safety trigger.  All the springs were rubbing together as well as on the end of the cable.

Then I looked at the other end of the cable.  It continued out through the swaged on ball that activated the throttle on the carb, and was to be put under a screw going into the block.

I had looked at the grip with attached cable, and the end to attach to the carb was different.  The cable did not continue on to become the ground for the kill switch.  There was another wire with a female clip on it that stopped near a turn the cable sheath makes under a clip that holds it in place.  On the old model like mine, under that hold down clip is a male clip on a wire that goes to the coil.  It looks like the new style wire will work fine by just taking that male clip out and plugging it into the female plug.

If I hadn't bought both pieces, I would have overlooked exactly how the old wire worked, and not only that, but WHY THE CABLE HAD BEEN BREAKING.  It wasn't breaking.  It was BURNING IN TWO.

I decided to just use the choke as the kill switch until someone doesn't remember to, and burning the cable in two.

I see why they changed the design, but the young guys didn't know.

I'll bet there are many of these FS450K's sitting in shops all over the country, and nobody knows what to do with them.  I paid $1100 for mine in 1999.  If you can find one cheap that doesn't work, buy it.

joe_indi

The throttle cable of your 1999 450 uses the inner insulated cable as one lead (connected to the ignition module via a clip)and the outer insulated sleeve as the other lead (ground, connected to the body via a screw on the cable support)
The newer one connects to the same points through wires from a micro switch in the handle.
I have had this issue with new cables on older models, brushcutters, trimmers and clearing saws.
The simplest solution is to fit a miniature push button switch on the powerhead and connect it to the same points.
Leave the cable to do only the throttle job.
When you want to stop the engine, just press the button till the engine stops. Once it is released it is back in the On position and ready to start.
Some of the newer Stihl products have a similar 'kill switch' instead of the Off position on the control.

Tom King


Tom King

Actually, the inner cable on mine continued past the carb linkage, and served as the ground.  The outer sheath contacted the lead to the coil inside a plastic clip/holddown for the cable assembly.  The original contact point to the coil was just a crimp on male connector that fits the new style cable.

Tom King

The choke works fine as a kill switch while it's idling.  I think I'll just open up the grip, and cut that spring that has a long tail touching the inner throttle cable.  Then no one will forget, and turn it off with the switch.

joe_indi

Tom King I would use the decompression valve to kill the engine at idle.
That would make it easier for the next start because using the choke floods the engine, which requires more pulls on the starter for the next startup

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