Jonsereds 49sp leaking fuel & oil

[jonsereds 621]

Yep you got problems...…...however your crank is not bent......these cranks do not bend.....they will break but will not be bent. What has happened is you counter weights have gone out of phase......this happens when someone uses a tool like a screwdriver to lock one side of the crank in place to remove either the flywheel or clutch nut. Under this type of strain the crank pin actually shifts/rotates slightly in one or the other of the counter weights. This can be realigned if you know someone with the equipment to do this type of work...….I find it much easier to simply replace with an in phase donor crank from another saw......you're gonna have the cases apart anyway so not a big deal really. You'll notice that you can't achieve a good chain adjustment with your crank in this state. If you adjust to the tight position it will be way loose after a small amount of rotation....if you adjust when it's loose it will be way to tight after some rotation.

Well....I suppose I should be glad I'm still learning ! From time to time I have used an impact wrench, even though I knew I know better......best to desist I think. Thanks for the heads up.

 

[Cantdog]

Well....I too have used an impact wrench but as with most things, in moderation. It's best to spread the holding of the crank across both counter weights evenly by using some form of piston stop. That way there is much less likely hood of sending the three piece crankshaft out of alignment.

 

[Cantdog]

Bump....you should look into this LesPro......

 

[sundance]

Bump....you should look into this LesPro......

@Cantdog : Look into what?

 

[Cantdog]

@Cantdog : Look into what?

Post # 39...….

 

[Bob95065]

Well....I too have used an impact wrench but as with most things, in moderation. It's best to spread the holding of the crank across both counter weights evenly by using some form of piston stop. That way there is much less likely hood of sending the three piece crankshaft out of alignment.

+1. You are in the hands of 49SP experts here - great advice from all. When I fixed my saw I read posts from the same folks and they gave me advice too.

When I am going through a saw like this the first thing I do is break the clutch and flywheel nut loose. In this case there is a clutch nut too. I remove the spark plug and get the piston near TDC by turning the crankshaft CCW. Next, take some clean starter rope and push it in the spark plug hole. This will stop the crankshaft from turning so you can loosen the nuts. Be sure you start near TDC to prevent getting the rope in the ports.

I went through a 49SP last winter that had a crankcase gasket leak. It was burning bar oil. I spit the cases and replaced the gasket with one I made. I bought gasket material and cut a new one. While I was in the there I re-ringed the piston, replaced the seals, gaskets and all the oil pump o-rings. I carefully measured the o-rings and bought replacements at a local supplier. I can look for the o-ring sizes if you are interested.

These are nice saws and worth fixing.

 

[sundance]

+1. You are in the hands of 49SP experts here - great advice from all. When I fixed my saw I read posts from the same folks and they gave me advice too.

When I am going through a saw like this the first thing I do is break the clutch and flywheel nut loose. In this case there is a clutch nut too. I remove the spark plug and get the piston near TDC by turning the crankshaft CCW. Next, take some clean starter rope and push it in the spark plug hole. This will stop the crankshaft from turning so you can loosen the nuts. Be sure you start near TDC to prevent getting the rope in the ports.

I went through a 49SP last winter that had a crankcase gasket leak. It was burning bar oil. I spit the cases and replaced the gasket with one I made. I bought gasket material and cut a new one. While I was in the there I re-ringed the piston, replaced the seals, gaskets and all the oil pump o-rings. I carefully measured the o-rings and bought replacements at a local supplier. I can look for the o-ring sizes if you are interested.

These are nice saws and worth fixing.

Yes, please look up the o-ring sizes. I try to keep repair notes for these saws. Really like mine.

 

[Bob95065]

This is what I used:

4 @ 5/8"id x 3/4"od x 1/16" thick - I found these dimensions on the board somewhere but I can't find the reference thread now. I know they should be metric but they work.
2 @ 5.6mm x 2.4mm

Make sure you get o-rings made from oil compatible material.

I bought the o-rings here:
Ace Seal, LLC
23 Las Colinas Lane, Suite 112
San Jose, CA 95119

Phone and Fax Info:

General:	408-513-1070
Toll-free:	800-223-7325
FAX local:	408-513-1074
FAX toll-free	800 329-1232

https://www.aceseal.com/
HTH

 

[Cantdog]

This is what I used:

4 @ 5/8"id x 3/4"od x 1/16" thick - I found these dimensions on the board somewhere but I can't find the reference thread now. I know they should be metric but they work.
2 @ 5.6mm x 2.4mm

Make sure you get o-rings made from oil compatible material.

I bought the o-rings here:
Ace Seal, LLC
23 Las Colinas Lane, Suite 112
San Jose, CA 95119

Phone and Fax Info:

General:	408-513-1070
Toll-free:	800-223-7325
FAX local:	408-513-1074
FAX toll-free	800 329-1232

https://www.aceseal.com/
HTH

Good info!! I have always had NOS o-ring sets in complete NLA gasket/seal sets and still have quite a few but eventually there will come a time when they will be spent so good to have he option!!

 

[Bob95065]

Another trick I use for making gaskets if you are in need of more than one is to print out the template on a piece of paper. When you are confident that the scaling is correct glue it to a piece of Masonite hardboard. Then I use a scroll saw and drill press to cut out the Masonite template. When I cut the gasket I put the Masonite with the glued-on pattern down and cut around it with a x-acto knife. This combines chainsaws with another hobby: woodworking

 

[Cantdog]

Another trick I use for making gaskets if you are in need of more than one is to print out the template on a piece of paper. When you are confident that the scaling is correct glue it to a piece of Masonite hardboard. Then I use a scroll saw and drill press to cut out the Masonite template. When I cut the gasket I put the Masonite with the glued-on pattern down and cut around it with a x-acto knife. This combines chainsaws with another hobby: woodworking

That's good!! I had a scanner/printer at the shop that would run 1/32" gasket material so I made sheets of templates on regular paper of common gaskets needed. This allowed me to orient small gaskets within the cavities of larger gaskets and get the most out of the gasket material. I could just scan the template page and print directly onto the gasket material...that worked fine. Have no idea if newer/better printers could/would handle paper that thick but my old HP would grab it get 'er done....

 

[Bob95065]

That is even better.

Cutting thin profiles with th scroll saw can be frustrating. Drill the holes first, cut the inside then the outside.

 

[Cantdog]

That is even better.

Cutting thin profiles with th scroll saw can be frustrating. Drill the holes first, cut the inside then the outside.

Yep no matter how you go about it or what gasket you're making doing the holes first is a must!!!

 

[Bob95065]

I hung on to an offcut when I put granite counters in my last house. I checked it with a straightedge to be sure it was flat. It's my surface plate now. I used it to lap the 49SP case halves prior to reassembly. Worked great.

That offcut surfaced a few Kohler cylinder heads too. I'm surprised how much use it gets.

 

[Cantdog]

I hung on to an offcut when I put granite counters in my last house. I checked it with a straightedge to be sure it was flat. It's my surface plate now. I used it to lap the 49SP case halves prior to reassembly. Worked great.

That offcut surfaced a few Kohler cylinder heads too. I'm surprised how much use it gets.

Always nice to have a truly flat spot to lap things like small cyl heads and these cases. I used the table top on my Unisaw to lap these 49SP cases.

 

[Bob95065]

Very nice work, both the case halves and the workbench.