Jonsered 670 question

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if you bought it new and its an old saw now and it must have done a fair bit of work by now so I would assume its the seals. as far as the compression side goes it will only need a new piston ring, you will feel a significant difference in the way it pulls over with new seals in, if the old ones are warn. stick the seals in and give her ago, I've just been looking in my pile of unopened stock and there's a jony 630 in there, been there 3 months, haven't even looked at it yet, in fact to be honest, I forgot I had it ;o) cd
It's cut mountains of wood. Only trouble I've had with it over the 20 some years I've owned it is every 2 or 3 years it needed a carb kit. It's giving me fits now shut hopefully the seals and o rings fix it.
 
It's cut mountains of wood. Only trouble I've had with it over the 20 some years I've owned it is every 2 or 3 years it needed a carb kit. It's giving me fits now shut hopefully the seals and o rings fix it.
I do think your seals will be the problem if they 20 years old they are bond to be tired ;o)
 
This is the 670 champ. All lines are new. Gas tank is plastic and 1 piece ignition. I know for a fact the seals and o rings were not changed. He did get the hi idle problem fixed. I checked the screen in the carb. It was clean. I better get o rings on the way. I'll be surprised if the seals and o rings aren't the prob. Like I said it's gotten bad enough that just as soon as it starts to warm up it dies and then you can't keep it running. Is that a symptom of seals going bad?

As far as I know, what leaking seal will cause are air leaks - and this doesn't sound like an air leak to me?

It actually sounds more like a coil or tank vent issue?
 
As far as I know, what leaking seal will cause are air leaks - and this doesn't sound like an air leak to me?

It actually sounds more like a coil or tank vent issue?
I think? if my memory serves me ? that he fitted a new coil, as it was one of the things I initially thought of. a failing (partially obstructed) tank vent would cause it to lack high rpm when running high revs, but it should still tick over all day long, if it's symptoms described are being interpreted accurately? a totally blocked tank vent would indeed cause it to stall eventually, but an easy remedy for this is, would be, when the saw cuts out, unscrew the fuel cap (depressurise),tighten fuel cap, then see if it starts again with a depressurised tank? kind regards cd
 
Yes, the simplest way to diagnose a tank vent issue is to either run the saw with the fuel cap open, and see if the issue disappears - or to open and close it when the issue appears, and see if it helps temporarily.

This is the simplest thing to rule in or out, so it is a natural "first step" in diagnosing, given the symptoms as I read them.
 
All lines are brand new as is the fuel filter. I had the carb kitted at the same time. Ran good for a couple of hours when I brought it home but got progressively worse to the point it will start but but then dies. It can't be adjusted to keep it running.. I noticed the foam doughnut which sits under the Dophragm on the carb missing

Including the impulse one (see the post by @Cantdog, a "Champ" qualifies a "a late one")?
 
Will
Yes, the simplest way to diagnose a tank vent issue is to either run the saw with the fuel cap open, and see if the issue disappears - or to open and close it when the issue appears, and see if it helps temporarily.

This is the simplest thing to rule in or out, so it is a natural "first step" in diagnosing, given the symptoms as I read them.
I will check that now.
 
Me to. It's cut mountains of Osage. Both green and dry. It's rock hard wood. Seals can't help but have wear. The Chinese coil does bother me. Would rather switch it for a factory 272 coil.
 

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