Stihl 028 eating spark plugs

[csservices]

Evening all, my old Stihl 028 AV super has suddenly taken to killing spark plugs, I had put it down to the only ones I had spare in my tool box were secondhand ones but fitted a new one last week and it has done the same, done 4-5 days work with it and then in the middle of a cut today back fired and cut out same thing when took the plug out only had a weak orange spark, put another plug in and away to go has run fine rest of day again, any ideas? cheers

[Rich2484]

More info required.

 

What state was the plug in. What plugs are you using. If you was to run a new plug for a tank of fuel what colour or shape is the plug in when you take it, before it goes boom?

[gensetsteve]

Sounds more like weak ign system ie coil. One or two of my saws have same plug for ten years cant remember the last time I had to remove one. I would say new plug just gives it the edge to run. Or its running very weak and hot and killing the plugs. Not really a petrol man more big diesels.

[Rich2484]

Depends on what part of the plug has gone and what colour the rest of it is to determin if fuel is an issue with over heating running rich or lean.

 

Is it a noticeable gone of plug as in electrodes destroyed or just not sparking.

 

Just seen you have said weak orange spark. First I would check the coil/flywheel gap. And check they are nice and clean.

[csservices]

Thanks will have a look, its spent quite a while in retirement but has had to be pressed back into service recently, the plugs usually black suggesting its running rich but doesnt smell rich when running or smoke, there is no damage to the actual plug when removed its just they don't spark/weak spark

[Rich2484]

If its been in retirement for a while you will find that the coil and flywheel will have a layer of rust on the contacts. Give this a good clean with spray and some emery. Ten check the spark again.

[GardenKit]

Try closing the gap on a 'dead' plug to that of a new plug. If it works again it could show that the coil is weak and can generate a spark until the gap increases slightly.

[spudulike]

The black plug suggests that the saw is running rich - lean it up on the H screw - it should be around 1 turn out - if it is this then check the airfilter is clean and if it is, lean it down 1/6th turn and try it again.

 

The coil may be on the way out but worth resetting the coil to flywheel gap by using a thin business card between the flywheel and coil and loosening the bolts and allowing the coil to stick to the magnet and doing them back up.

 

Try that for starters:thumbup:

[spudulike]

If its been in retirement for a while you will find that the coil and flywheel will have a layer of rust on the contacts. Give this a good clean with spray and some emery. Ten check the spark again.

 

Those aren't contacts Rich- just magnets and the laminated steel core of the coil that picks up the change in magnetism to generate the HT - worth making sure it is relatively clean but they don't do any contacting matey:001_tt2:

[Rich2484]

Those aren't contacts Rich- just magnets and the laminated steel core of the coil that picks up the change in magnetism to generate the HT - worth making sure it is relatively clean but they don't do any contacting matey:001_tt2:

 

Well for simple folks they are the contact points. Or areas. It's easier than trying to type the while of what you have had to. :001_tt2: