066 has funny looking piston

[PES+]

An addition.......tailed or eared clips rotate.....the double more than the single as I have proven to myself by marking customer saws.

The non ear/tailed pretty much stay put.

I too only use non ear/tailed clips in any hi output situation.

I do not recall many Stihl pistons that do not have the clip recess cast right into the piston though.

Dolmar and Solo the same.

The Huskies need modification to use the non eared clips.

 

[pdqdl]

I seem to have been less than clear.

No one seems to have commented, so I am beginning to doubt myself here.

Doesn't the bearing inside that scored piston look totally burnt up, with tapered/fractured ends ?

I was not referring to the roller bearing on the wrist pin, I meant to type "bushing", but I goofed. Isn't that a bushing located inside the wrist pin bore on the piston ?

It still doesn't look right to me.

 

[PES+]

No.....the piston pin bore is machined right into the piston.

The damage was from the clip ears breaking off it would appear.

 

[Lakeside53]

Yes, toss the POS chinese clips in the garbage... USE OEM clips BUT, as came up recently with Baileys piston, the grooves were not the correct size for an OEM clip...

Classic... used a cheap piston to save a few $$ and toasted the saw... This is exactly why I won't fit them in customers saws.

 

[blsnelling]

I doubt this can be blamed on the piston. More than likely it was operator error on the builder part. He probably bent the clip. I do understand using OEM only in a dealership environment though.

 

[Lakeside53]

The Chinese clips are crap... been there... hard for the operator to to bend one with ears excessively.... Bailey's had trouble with these clips also.


I've seen both wrong sizes and lack of tensile strength. Ears breaking off is why Stihl abandonded them when the saws went over 11,000 (?) rpm.

 

[Mad Professor]

Crank side rod bearing $#!t the bed.

Whoops, didn't see the pics of the circlips on pg. 2

 

[timberwolf]

A saw turning 13,500 RPM puts about 145,000 ft/s/s of acceleration into piston components when the crank hits TDC. Thats 4500 times the force of gravity. So even a small tail 1mm in diamiter by 4mm long weighing 0.025 grams will experience over 115 grams of upward force. that about 1/4 lb. Then at BDC force is about 2500 G in the opposite direction or 64 grams of force (a little more than 1/8 of a lb). With that much flexing nearly one million times an hour it's easy to see why the do on occasion fatigue and break.

If the tails are placed to the side the force is crossways on the tail and is the worst for flexing at the root of the tail. If the tails are placed at the bottom the wight of the tails pulls up on the whole clip hard at TDC, but if the tails are up the the worst of the acceleration force is directed staight up into the piston without being put into the clip it's self.

Attached a graph of piston acceleration stock 066.

so, if you have a tail, PUT YOUR TAIL UP. :monkey:

 

[PES+]

One of the problems

I doubt this can be blamed on the piston. More than likely it was operator error on the builder part. He probably bent the clip. I do understand using OEM only in a dealership environment though.

A good clip should not be able to BE bent unless the installer does something really out of the ordinary.

The clips need to be able to retain their shape through repeated flexing.

I have seen clips that that bend and stay bent when you pull the ears together to install them.....and no I do not and will not install such a clip....causes arguments when working for others but I won't do it.

I have seen people spend time reforming these soft clips because they think the new soft clip is better than a good non damaged used clip.

The "good" or intact clip that is shown in the pictures on this thread are the worst of the worst as the two ears are of different lengths and bend so this is set up to really get rotating in operation.