Placing a 066 big bore

[mdaalmeijer]

Hi,

My 066 cylinder got busted after years of flawless running. Bought a new 660. Now i want to refit the old one with a big bore kit. Just for the fun of it. I received the big bore kit the other day and now i have been searching for information on how to proceed.

So far i found that the BB can be trouble some but hey, i'll give the saw to my old man to saw up about 35 good sized pine trees that have been blown down in the storm we had this winter.

Can somebody explain me what squish is and how to go about measuring it?

Also i have been wondering how to put on the cylinder rings with out breaking them or damaging the piston. Same for moving the piston in to the cylinder with out damage?

My mechanical skills are fair enuf however this will be the first time to replace a cylinder and so all information is welcome. I am sure all this has been dealt with on this site in the past. So if somebody knows in which post to look, that would be very helpful.

Regards,
maarten

 

[gink595]

Wow, ran flawless for years. Must be nice. Mine ran flawless for about 3 tanks and then a ring broke:censored:!!

Guys are using soildering soilder and putting it in throught the plug hole and then run the piston up until it squises the soldier. Than take a caliper and measure what the squish is. Make sure the soldier reaches the outer cylinder wall on the squish band.

As for removing the cylinder rings... be careful and use common sense. Same with the circlips on the piston. As someone once mentioned to make sure the room you are working in is free of noise and completely silent. So you can hear the general area when the circlip goes flying out a million miles an hour

 

[mdaalmeijer]

Thanks for your reply but what is squish? I have no idea what to measure is and why.

 

[Wet1]

http://www.sacoriver.net/~red/squish.html

 

[gink595]

Squish is the distance between your piston at top dead center (TDC)and the cylinder squish band. It effects the compression of the motor, the less squish the higher the compression. So if you measure the squish and it reads .035 and you take the base gasket out and it reads .023 you will have more compression and more power.

You would want to measure it to make sure that you are in a safe range and that your piston isn't getting to close to your cylinder squish band. If I'm remembering right my BB with cylinder base gasket measured .032, When I tried running it without the base gasket the piston actually hit the top of the cylinder (squish band). So I had to use a base gasket. I believe there is different thicknesses of base gaskets but not 100% on that.

I would assemble it and pull the motor over carefully to make sure that everything clears. And then check your squish. The piston skirt was very very close to the case also. But it ran okay, I did have some concern that I would have to relief the case for the piston skirt to clear.

 

[user 19670]

As someone once mentioned to make sure the room you are working in is free of noise and completely silent. So you can hear the general area when the circlip goes flying out a million miles an hour

You guys reuse the clips? When I learned engine rebuilding it was advised not to reuse the pin retainers. Of course that was with motorcycle engines and the consequences of a failure could be dire.

 

[gink595]

You guys reuse the clips? When I learned engine rebuilding it was advised not to reuse the pin retainers. Of course that was with motorcycle engines and the consequences of a failure could be dire.

I haven't reused any circlips, I usually end up destroying them trying to take them out. I was referring to installing them

 

[Freakingstang]

don't reuse the circlips

when checking squish, use a thin very thin solder and I like to make a rounded triangle that is almost the diameter of the piston. This gives you multiple contact points for more accuracy and this is the key, there won't be piston rock if you are checking it in more than one spot without rings.

And yes, there are two thickness 066/660 bases gaskets. I would not recommend using the thicker gasket as it is paper and will lose it's seal over time as the bolts loosen, whereas the thinner is a compression type metal gasket that keeps constant even pressure on the base bolts to keep them from backing/loosening with prolonged vibration.

common sense should tell you not to reuse the gasket, so measure the squish with the old gasket in place and save the new one for once you assemble it for good.

 

[mdaalmeijer]

Hey guys thanks for the replies.

Do i need to change the sprayers in the carb to get her running as should. Or can i just get her on the right track with the one that is in there?

 

[Tzed250]

Do not use the clips that come with the big bore kit. Get a set of OEM Stihl circlips.

 

[mdaalmeijer]

Will do, thanks for the tip.

Yeah the clips don't look like much