scored piston on 460

[65x55BPD]

The organization i work for has many saws and many novice operators. that means i so alot of saw maintenance and repair. i kind of learn things as i go along.

we had a 460 that is about 1 1/2 old. somebody apprently "purged the saw" when it started to run high beofre it runs out of gas he just kept on running it till it was completely out. after that the saw would not start. we took it to a stihl shop and they said the piston was scored because when it was being run out it was running on gas vapors and the oil could not lubricate the piston. I dont know if i buy this explanation. they said it was not worht repair. this was about 3 months ago. just this week i was bored in the shop so i tore the saw apart. when i took off the muffler i could see a little bit of scoring. i cleaned out the carbeurator and the lines. when i put it all together it ran fine except it seems a little too hot. the bar heats up pretty quick, as does the clutch cover. the saw was considered dead so its no big deal for me to run it and maybe inflict more damage.

does anybody know whats going on with it?

 

[BostonBull]

There have been many an argument here on this subject. Maybe he sucked something up through the filter and clogged the lines? Maybe he hit something while cutting and the bottom end got a good whack? Too many variables. Maybe Lakeside will put his .02 in for us, hes a good tech.

 

[Dadatwins]

You can score a piston by running a saw out of gas, saw leans out and piston will score. New piston and head probably around a $200 item plus labor, so I would not say an $800 saw is "not worth fixing". If the bar is "heating up" check the bar oiler, does it have oil in it? Could the chain brake be on? broken? No bar oil or a locked/broken chainbrake will destroy bar, chain, clutch and probably tear out the crankshaft seal and bearing eventually from the heat. Combine all that damage with a blown piston and head and it might be getting close to scrap pile.

 

[Lakeside53]

I'm in agreement with Dada.

Goosing the last gas out of a saw will damage it, maybe not all at once, but if it's done often enough, it will definitely damage the piston,cylinder etc. I recently had a near new MS660 that cooked the piston in a day with the operator doing this while cutting big stumps.

Hard to know what's going on in the engine without a pressure, vac and compression test. The bar overheating is separate problem. Take the bar and chain off and see if it does the same thing. I assume the brake is off?

After lean damage, most cylinders can be saved; most pistons should be thrown. A NEW Stihl piston/cylinder set is $315 list... The piston alone is $131. If you do it yourself, it's worth it if the rest of the saw is in reasonable condition.

 

[RED-85-Z51]

Ive never heard of a saw being totalled out by running it dry one time..

I know on micro 2 strokes, like those in Nitro R/C cars, are prone to major damage when one flips over because it runs too lean, but the problem is not the lack of oil, it is the extremely high RPMS associated with running lean.

Ive run countless saws out of gas, and Ive never had one die on me, yet.

Seeing as he ran it dry, is there a possibility he picked up some crap in the bottom of the tank? Water..some debris..maybe?

 

[65x55BPD]

thanks for clearing up about running the saw out of fuel.

i dont think its a bar oil issue for a few reasons
1. it was throwing enough oil when i held the bar away from a piece of wood
2. its got oil in the tank
3. the holes in the bar for the oil are not clogged
4. its not just the bar thats heating up(my mistake on the post) its the the whole saw(pull start case, oil tank etc.)

does somebody know of a step by step to do a piston/cylinder set. ive never done that and i only know saws by doing, ive never been told anything.

 

[RED-85-Z51]

thanks for clearing up about running the saw out of fuel.

i dont think its a bar oil issue for a few reasons
1. it was throwing enough oil when i held the bar away from a piece of wood
2. its got oil in the tank
3. the holes in the bar for the oil are not clogged
4. its not just the bar thats heating up(my mistake on the post) its the the whole saw(pull start case, oil tank etc.)

does somebody know of a step by step to do a piston/cylinder set. ive never done that and i only know saws by doing, ive never been told anything.

Its not uncommon for a saw to heat the cases and such up.

Might try richening the mixture up, try and cool it down with fuel?

It is absolutely common for the clutch cover, and top covers to get very hot. The clutch gets hot, and the cylinder/muffler get very hot, not to mention the flywheel blows hot air all through the hot fins, and into the covers, which funnel the heated air away from the saw.

Do a compression test first, there is a good chance the saw is fine, just needs some tuning.

 

[NWCS]

an overlooked option is a Baileys BigBore kit that comes with cyl, piston, rings, pin and clips for around $120 shipped. say you were also having the saw modified by me, thats $200, that 200 gets the BigBore kit modified and installed on your saw, right here your still less than just the Stihl piston/cyl set. even the price of shipping the saw to me your money ahead and getting way more power than stock..

total price of the woods port mod and BB kit from me: $320
hows that for a deal? that has a 45 day warranty too.

 

[tek9tim]

I roasted a Forest Service 046 by running it out of gas once. Just trying to get that last tree limbed. Didn't even let it rev out high, feathered the throttle. Melted 'er down. I was ignorant and in a hurry.