Jonsered 670

[Burchie70]

Bought a ‘86 Jonsered 670 which was all oem p&c. It ran when I bought it but never put it in wood. I recently cleaned it all up and changed the base gasket, exhaust gasket, carb kit and intake gaskets. I’m getting 160 for the compression and it has a 230A carb on it. I started it today and it runs great but a few seconds into a cut it stalls out at wide open. It stays running when it’s not under a load at wide open and idles fine. I have the carb set at 1 turn out on high and low. I screwed with the carb and can’t get it right. Any ideas what would cause it to do this ? Thanks

 

[Totembear]

Maybe coil...

 

[Burchie70]

I didn’t think of that. I have a 266xp with a 2 piece coil, wonder if they’re interchangeable. I’ll have to look at the part numbers. I bet those coils are hard to find and pretty pricey. Thanks

 

[HiOctane]

Try opening H a bit,you are probably too lean in the cut. Same two pieces ignition on both saws.

 

[Spottedgum]

Check your fuel line between the tank and carb.
If the line is pinched, the tank pickup filter is dirty, or the line is closed up where it goes through the tank body, you will starve for fuel and have the symptoms you are experiencing.
Clogged exhaust port or spark arrestor will do the same.

 

[SEAM]

Also check for clogged fuel filter and debris in tank ...

 

[Burchie70]

Ok thanks guys. I cleaned the tank and filter when I tore the saw apart but I’ll check it again and also check the fuel line. I did a muffler mod so it’s not the spark arrestor. I’ll check everything tomorrow

 

[Cantdog]

Ok thanks guys. I cleaned the tank and filter when I tore the saw apart but I’ll check it again and also check the fuel line. I did a muffler mod so it’s not the spark arrestor. I’ll check everything tomorrow

One other thing to check is the final fuel filter in the carb body. Simply remove the top cover, gasket etc. of the carb. It is a screen located down in a hole about 1/4" in diameter right where the fuel comes into the carb body. This may well be partially clogged and not allowing enough fuel in to run at high speed for very long. Though it may allow enough to fuel to idle properly.

 

[rupedoggy]

metering lever to low

 

[Burchie70]

Thanks guys, I didn’t get a chance to tear it apart today I got to busy. I’ll post what I find after I get it apart

 

[leeha]

Muff mod means you need more fuel. Open your HI and possibly the low as well.

 

[Chainmale]

Could check tank vent while you're going through everything too

 

[Burchie70]

Finally got a chance to pull the 670 apart. Fuel line and filter are good, pulled the carb apart and checked the metering lever and it’s level with the carb deck and the screen in the carb had no sediment in it. I tried running it again and it makes 4-5 cuts through a log running good then it starts to starve for fuel and eventually quits. I tried opening up the high a little more and it doesn’t help. I still have to check the tank vent and I will pull the coil off my 266 and try that also.

 

[smokey7]

Check the impulse line from the jug to top of the carb too. I'm wondering why you changed your base gasket? Did you base gasket delete it? Double check your work there.

 

[Burchie70]

Check the impulse line from the jug to top of the carb too. I'm wondering why you changed your base gasket? Did you base gasket delete it? Double check your work there.

I was gonna delete the base gasket but I couldn’t get the squish where it needed to be. It would’ve been way to tight. I was going to use a aluminum can but still to tight. The impulse line is fine but I may have found a small air leak on the rubber intake boot. I’m waiting on a new wire clamp to put it back together and try it. I used hondabond on the intake and still had a small air leak.

 

[smokey7]

Good deal this series of saws are my favorite to build. You can have 60 to 72cc and so many cylinder options it's silly.

 

[KASH]

I had a Jonsereds 670 the high and low speed needles would turn in on their own while I was cutting,I had to use blue locktite.I have not given it the long run time test.
Did you fix your saw.
Kash

 

[smokey7]

Just replace the springs on the h&l screws.

 

[Burchie70]

I pulled the carb apart again, resealed the intake boot, changed the fuel line and tank vent and it runs good now

 

[mogulmasher]

I was gonna delete the base gasket but I couldn’t get the squish where it needed to be. It would’ve been way to tight. I was going to use a aluminum can but still to tight. The impulse line is fine but I may have found a small air leak on the rubber intake boot. I’m waiting on a new wire clamp to put it back together and try it. I used hondabond on the intake and still had a small air leak.

What were you getting for squish? I just rebuilt my 670 Champ and measured .024" with gasket deleted.

Now I'm suffering from an air leak somewhere on mine. It's got new crank seals and oil pump o-ring. I'm thinking I might need to put base gasket in, wondering if maybe cylinder base isn't square or something.