Stihl 066 (old version) Problems

[simonUK]

Evening gents
Long time since i posted but I have always been sitting in the background.
I need to ask a favour. I rebuilt a Stihl 066 about a month ago had to split the case to because a bearing was rough.
Replaced the bearing and case gasket and seals. I then went on to sell it.
The guy said it ran ok for a couple of cuts apparently.
But then he said it just stopped. So I accepted it for a full refund.
The saw left me running absolutely fine but whehn it came back it had a severley scored piston and an air leak to the seal on the flywheel side.
Thankfully the cylinder cleaned up fine. So just a new piston and seal and it should be ok.
But to get to the ultimate point what is the best way of installing a seal and how far down should it go. I dont want to lose such a considerable amount of money again
Thanks in advance
Simon

 

[Buzsaw]

Stihl actually has a seal tool which sets it ( think about 1/8" it sets the seal in). Always do a vacum test on the saw especially when you replace the seals.

 

[Bowtie]

Which bearing did you replace? The Clutch side bearing is easy to install wrong because it does not bottom out in the case like the flywheel side. If the bearing is indexed wrong, the seal can interfere with the oiler/clutch components, or rub on the crank throw.

There is a way to install a clutch bearing in that style case without the Stihl tool. Some disagree but it has worked for me. What I do is put the bearing in the freezer, and use a heat gun (or your wife's hair dryer works good) and heat the case *WITH THE OIL PUMP INSTALLED*

Next you install the bearing from the crank side quickly and carefully until it GENTLY touches the oiler. Then let stuff cool, and install the seal. I install them on the clutch side flush with the bearing lip.