Fuel Boiling In Older Jonserad

[gfadvm]

I have an older Jonserad with a 16" bar (don't remember the model#). It starts, runs, and cuts fine but the fuel in the tank is boiling every time I check it. Is this a problem? Dangerous? I'm the worlds worst chainsaw mechanic but can follow instructions if someone here has a fix. Thanks.  PS: I had an old Husky that did this for almost 30 years and I just ignored it.

[HolmenTree]

I made a living with Jonsereds saws starting in 1974 with a 621 with the solid fuel tank to crankcase design and  the last one was a 920. On a hot summer day yes the gas would bubble but not boiling from heat, more from being warm and vibration causing the bubbles and pressure released when the gas cap was opened to check fuel level. Like opening a can of warm soda pop. I remember putting my finger in the gas and it didn't burn my finger :D
Never was a safety issue and the saws ran perfectly fine.
I think my 910 and 920 had a spacer barrier between the crankcase and fuel tank to cut down on thermal transfer.
What model Husky did you have with the metal solid tank housing?

[gfadvm]

Holmen Tree, Thanks for the quick reply. I too stuck my finger in the "boiling" fuel and it didn't seem hot. I will check the Model# tomorrow and get back to you. The fuel does continue to "boil" even with the saw off.

[Cedar Savage]

I ran Jonny Red 621's & 80's back in the 1970's too. I remember the gas boiling on hot days in the summer, & some times vapor locking. We would try to buy gas that didn't have any alcohol, an that seemed to make a difference. Those were some heavy saws, that held up real well. 

[sharkey]

Dont forget the ethanol content.  Some places have 10%, some have more.  Ethanol boils 40 degrees below water at 172 F.   

[old guy]

I had a 910e back about 1981, I think that was the year they came out.
  That saw would roil or boil the gas in the tank also and when it was shut off under those conditions it would not start again until it cooled off, it was a mean cutting machine tho.

  John

[joe_indi]

The decreasing fuel level in the fuel tank causes a low pressure inside. The tank vent is there to allow air into the tank when the pressure drops beyond a point. But if the tank vent does not function properly the pressure keeps dropping to a point that the air mixed in the fuel starts getting released to fill up the low pressure.This is the 'boiling' that we see. As Cedar Savage mentioned the result would be  unwanted vapor locks.

On some saws and brush cutters there is something we call a primer.
Its function is not to prime but to purge the fuel lines and carburetor of air formed by such boiling that could lead to vapor locks.

[5000+]

Very normal on saws with a one piece metal crankcase/fuel tank. 
Lots of engine heat transferred to the fuel and tank.  Letting the saw idle for a minute or two before shutting off can help. 

[HolmenTree]

I thought I'd post some  Jonsereds nostalgia from the summer of 1977.
First photo is Jonsereds engineers making in roads in North America and second photo is Swedish loggers back in their homeland of Sweden.
I always had a soft spot in my heart for the original Jonsereds seeing my first saw that I made a living with was a Jonsereds 621. I owned the last true Jonsereds in 1979 before being bought out by Electrolux and that was a 910E, a fantastic power to weight ratio saw even in todays standards.


  

 

[old guy]

Completely agree with you Holmantree, that saw was an animal.

  John

[HolmenTree]

Completely agree with you Holmantree, that saw was an animal.

  John

Thanks John, and from information I found out on Magnus's Chainsaw Collectors se. site Jonsereds developed a 100cc 910 that got lost during the Electrolux transition period.

[Cedar Savage]

Joe hit the nail on the head with his explaination...
Those pic of ads are great Holmem... Thanx....brought back memories.
In 1977 I bought a brand new 70E,  had ta float a loan at the bank & get a cosigner.
Man was I proud of that saw, wore it plumb out, making a living, dropping trees for a C-5 cable machine, & cutting firewood off the landings in the evenings after work, for the next several years.

[chet]

My first new to me saws were all Johnnys; 52E, 70E and a 90. They are all retired now, but still sit proudly on a self in my garage. Man I loved them saws. 

[HolmenTree]

My first new to me saws were all Johnnys; 52E, 70E and a 90. They are all retired now, but still sit proudly on a self in my garage. Man I loved them saws. 

I may have told this story here before but here goes.
Last year I removed some trees for a elderly customer with my Husky 372XP and told him I'd buck them up for him into firewood length.
He replied "That's OK I'll go get my Jonsered". So while I was off in the distance grinding his stumps I could see him bucking the logs with an old black top Jonsered what I thought without taking a 2nd look would only be a 70E, but it was cutting way faster then a 70E .
So I had to go up to him and check this saw out and low and behold he had a almost brand new looking Jonsered 90 with all the decals still intact.
I offered him $300 for the saw but he declined and he said "the logger who sold me this saw 30 years ago still tells me whenever we cross paths that I should never have sold that 90 to you." 

I owned a 90 before I bought my 910 and  it was one durable torque blessed saw.