Jonsereds 49sp does not start

[dave ensign]

Today most carb kits come with two sets of reed valves for gas or ethanol. By chance were both used?

 

[Bart01]

to get some things out of the way :
- Muffler is free
- Fuel filter inside the carb is clean and has been replaced
- I only used one reed valve in the carb and gaskets are placed correct
- choke has been closed to try to start
- Tank vent has been removed to make sure that that is not the problem
- I have placed a new transparent fuel hose. I can see that the fuel does not travel up the hose while trying to start.
- if i pour fuel in the spark plug hole, the saw does start, but stops after a few seconds...

First thing i'm going to do is a pressure test on the cylinder. I believe the grease test was a sign that no pressure is going in or out the impuls hole...
I will keep you updated on my progress. You guys have given me a lot of tips !

 

[Old2stroke]

to get some things out of the way :
- Muffler is free
- Fuel filter inside the carb is clean and has been replaced
- I only used one reed valve in the carb and gaskets are placed correct
- choke has been closed to try to start
- Tank vent has been removed to make sure that that is not the problem
- I have placed a new transparent fuel hose. I can see that the fuel does not travel up the hose while trying to start.
- if i pour fuel in the spark plug hole, the saw does start, but stops after a few seconds...

First thing i'm going to do is a pressure test on the cylinder. I believe the grease test was a sign that no pressure is going in or out the impuls hole...
I will keep you updated on my progress. You guys have given me a lot of tips !

I'm hoping when you say you are going to pressure test the cylinder, you mean the crankcase?
To avoid confusion, you have to stop calling the fuel pump diaphragm a "reed valve". Reed valve is an entirely different device and has nothing to do with a carb.

 

[Cantdog]

I assume that when you did your grease test the Sparkplug was installed… yes?

 

[dave ensign]

OK what ever you want to call the carb valve. Not the diaphragm.

 

[jonsereds 621]

I am not clear about what op means by "I only used one reed valve". There is one spring loaded pivot lever operated fuel valve operated by tit on respective diaphragm ( with gasket next to carb body ). There are also two flap valves as a part of the other of the two diaphragms. This diaphragm MUST be placed directly against carb body (with gasket on outer side) and the two flap valves MUST be orientated over the two corresponding fuel passages in carb body. Often there is a telltale shadow on carb body which indicates the correct position . Carb kit may not have come with exploded diagram clearly showing order of reassembly. Are we CERTAIN this is all correct ? If gasket is on the wrong side of flap valved diaphragm it will be unable to pump as flaps cannot cover fuel passages as intended.

 

[Bart01]

Hi guys !
A little update on my progress :
I did a crankcase pressure test (see photo) and it did not held pressure for 1 second...
So i took off the carb and muffler and at closer inspection i could see that the cilinder head was lose and there where no washers between the bolts... Removed the cilinder head and the gasket was also in very bad condition.
New gasket and proper washers between the head and bolts and bolted everything back together.
New pressure/vaccuum test : it now holds pressure and vaccuum !

Because the compression test was good and the guy who sold it to me said he had used it before i assumed that the piston and cilinder where good.... how wrong i could be !

 

[Bart01]

The result :
a nice working Jonsereds 49sp ! saved from the scrapheap.
Thank you guys for all the help !! I learned so much !
Arboristsite rules !

 

[dave ensign]

Glad you got the old girl going.

Dave

 

[Cantdog]

Glad you got it sorted out........but.......you better fold down the locking tabs onto a flat on your muffler bolts or you'll be looking for them in the sawdust pile...important.....

 

[dave ensign]

Cantdog

Who is your eye Doctor. I want him or her. BTW I just did another 49 from a parts box.

Dave

 

[Bart01]

good advice just keeps coming
yes, the 49 is a nice running saw. A bit less heavy than my 621 (but still my favorite)
I just love the feeling of restoring a vintage saw and running it for the first time ! A bit of an addiction i guess

 

[Cantdog]

Cantdog

Who is your eye Doctor. I want him or her. BTW I just did another 49 from a parts box.

Dave

LOL.......it's not eyesight so much as knowing what to look for. Having owned, used and rebuilt the 49SP saws for the last 47 years it's pretty automatic. My go to saw is still my original 49SP that I bought new in April of 1977, though I have a dozen or more running examples, that one is special.

 

[Bart01]

Now that we are showing off our equipment
This is my 621 (49sp in the back)
The 621 was the saw of my grandfather, so it's special for me too... Don't know the exact year, somewhere early 70's... Still have the original bar cover !

 

[Cantdog]

That's a well used 621.....spent many hours in your Grandfather's hands!! Hard to tell the year but it is an early one by the black and white sticker
Arguably the finest Jonsereds ever made!!!