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670 Jonsered power build. Need input please

Kozak Logging

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Hi guys, new here. I have a old Jonsered 670 I used to run for many years. I have new saws and want to build it for power and longitivity at the same time. I need input as far as what all I can do to squeeze max power out of it. If I remember right all I have ever done is install a new stock piston and rings. Should a guy go with a new rod/crank assembly? Where do I start?
 

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Don't know if it has limiters on it but that would be the first thing I would do get rid of them.Then a Muffler Mod:biggrin: open it up if it needs it.
 

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Don't know if it has limiters on it but that would be the first thing I would do get rid of them.Then a Muffler Mod:biggrin: open it up if it needs it.
I will definately be doing the muffler mod, but I want to do a actual build on internals too. Is there any aftermarket pistons/performance parts? Can they be bored? I just did a std piston and rings a while ago.
 

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You seem to be concerned about the crankshaft,if you have play in the crankshaft it's possible you need crank bearings,or worse case scenario a crankshaft also.
The reason I'm concerned, is because the crank was never serviced besides outter bearings and seals. I forgot if the rod is bolted in a two piece or if its just one.
 

huskihl

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While a 670 is a fantastic saw, one thing to keep in mind is parts aren't being made anymore. Some parts are interchangeable with a husky 266 or 268 though such as pistons, clutches, handles,... There are a few used parts available also. Pretty cool old saws. I have 2
 

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While a 670 is a fantastic saw, one thing to keep in mind is parts aren't being made anymore. Some parts are interchangeable with a husky 266 or 268 though such as pistons, clutches, handles,... There are a few used parts available also. Pretty cool old saws. I have 2
I still have a 630 saw too. Still runs, just sits there with no bar like the 670 does. I run a jonsered 2159C and my dad just got a husky thats a little smaller. Adirondackstihl, a great guy let me tell you. He just did a modded muffler for it, to get rid of the cat setup.
 

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The cylinder is a lot like the 268 husky. They can be improved on with more compression and some grinding in the cylinder.
 

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The cylinder is a lot like the 268 husky. They can be improved on with more compression and some grinding in the cylinder.
Whats needs to be ground? the bottom by the skirt to clear the rod from hitting on the front and back? What size piston then and what do I order exactly?
 

huskihl

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I still have a 630 saw too. Still runs, just sits there with no bar like the 670 does. I run a jonsered 2159C and my dad just got a husky thats a little smaller. Adirondackstihl, a great guy let me tell you. He just did a modded muffler for it, to get rid of the cat setup.
Well now you're talkin'. Build the hell outta the 670 and keep the 630 for parts. But if you have it ported, I'd spend the extra little $ and get new crank bearings
 

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Stick with the cylinder you have. Stock piston is fine. Have the base and chamber cut to bump compression. If you want a fast saw with 20" bar then you don't want to go crazy on compression. If you're going for long bar torque a little more compression will work. You'll be raising the exhaust a couple degrees after machine work. The transfers will need to be raised as well. Widen the intake out and square it up but don't lower it.
 

Adirondackstihl

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He's looking to do some bolt on garage mods guys. I mentioned maybe retro fitting a 288 HD intake horn so he can upgrade the AF. Not sure if that's possible but I'm pretty sure it can be done.

Craig, saw cylinders are like the newer sled and bike cylinders. They are nikasil plated and cannot be bored unless you want to dish out $ to send it to US Chrome to be re-lined.
At that point you'll need to figure out what bore you're looking to achieve and find a suitable replacement piston. Or worse, have to pay to have a custom slug made.

I think you're best bet is to freshen the top end with a new set of rings, wp bearing, muffler mod and go from there.

If that's not enough, send it to be ported.
There is a handful of reputable builders I would trust my 1st born with (well there's only one if trust to babysit and even then it's questionable) but be prepared to shell out $300-$350.
You won't be disappointed in the performance
 

mdavlee

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The 670 had a west coast setup for a stack or big filter. You may luck up and find one. If not you could probably get a velocity stack to fit for a husky.

For the garage with no machine work get a degree wheel and check squish to see if it can be run gasketless. I think I have a degree wheel printed on cardboard on a drill chuck you could have for shipping. Give you something to start with anyway.
 

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Stick with the cylinder you have. Stock piston is fine. Have the base and chamber cut to bump compression. If you want a fast saw with 20" bar then you don't want to go crazy on compression. If you're going for long bar torque a little more compression will work. You'll be raising the exhaust a couple degrees after machine work. The transfers will need to be raised as well. Widen the intake out and square it up but don't lower it.
Honestly, we run 20's on all our saws. But I think this saw here I want to run a bigger bar, i know they make a 24", but maybe want to go one a little bigger, but probably will settle with a 24" bar. Perhaps a skip tooth chain.
 

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Honestly, we run 20's on all our saws. But I think this saw here I want to run a bigger bar, i know they make a 24", but maybe want to go one a little bigger, but probably will settle with a 24" bar. Perhaps a skip tooth chain.
24" for speed stick with full comp. Unless you're in real stringy wood that clogs with chips too easy then skip is slower.
 
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