Thread: Worked on my Jonsered 49SP today....

Worked on my Jonsered 49SP today. It started out by truing the bar. Then I thought....I should pull the muffler and see what the piston looks like. Well there is/are some scoring. The muffler port was all carboned up. So, I started scrapping and carbon got everywhere...so, I took the air hose and blew it out...not thinking about the intake ports being open to the crankcase which got the bits of carbon in it. Now...I need to get that out of there...so apart came the saw.

The ring was partly stuck to the piston. Piston is scored and the ring grove closed up a bit because of this. I spent some time getting the carbon off of the piston in the wristpin area(wristpin would stick on the carbon build up in the hole in the piston), ring grove, and the top. Now the ring is free to expand and contract withing the groove. Ring contact with the cylinder is a plus. I probably will replace the piston and ring some time in the feature.

I flushed the crankcase twice with mixed gas. I'm glad I did because the gunk in the crankcase turned turned the gas black both times.

On reassembly I took some 2 stroke oil on the crank bearings, piston, ring, and wristpin.

I didn't do a compression check before I did the work because I wasn't planning on taring the saw down. I should give it a check after a few tanks of mix.

I think it has more power.. it starts better and after a carb adjustment I think it idles better.

This is probably better than the mod I mention in this thread:

Did a power mod on my Jonsered 49sp!

Thanks for taking a peek!

Dan

Well good luck in finding a piston for a 49sp.


Just so you know the pre epa (44mm) Husky 350 piston ring fits perfectly.

mod-Mark

I'll keep that in mind! Thanks for the heads up!

Dan

I don't know if it's still there but a day or two ago someone had a piston and cylinder listed on ebay.

If you think you need one, better snatch it up, there hard to come by.

254 olympic piston will work!

Originally Posted by Javelin

254 olympic piston will work!

Really? Where were you a year or so ago

Second thought, I'll bet the 245 Oly pistons grow on trees don't they!

I will check I might have a few left! I use to use them alot! I do not know if they are still available from efco because I am no longer a dealer with them thanks to there worthless dist. here! But that is a long story!

I ran a tank of fuel through today. It seems like it has more power. I'll post back after a few more tanks.


Dan

Originally Posted by Modifiedmark

Well good luck in finding a piston for a 49sp.


Just so you know the pre epa (44mm) Husky 350 piston ring fits perfectly.

Yep your correct, been there done that worked great still got the piston, brand new minus the ring, have no use for the piston though.

My dad has an old jonsered 49sp that still runs great. It was our firewood saw last year until something happened with the points on it. What would it be worth? Oiler works good, chain brake works good, saw runs good, starts and idles fine, no bogging of flat spots in the power. Anyway I was just wondering if you know what it might be worth to someone? Still needs the points replaced or bypassed.

Thanks

49SP's are one of my favorites; I've got 4 of them. They will hold their own with todays 50CC class leaders, including the 2153/346 and 5100S. I have customers that still use these saws on a regular basis.

ModifiedMark is right about trying to find a piston for them. NLA for quite a while now. I second the motion about the early 350 ring working. I didn't know about the 254 Olympyk piston. Is it domed like the 49SP piston is, and is it still available?

49SP's are pretty easy to work on, but parts are pretty scarce beyond starter springs and sprockets. There is some interchangability with Jonsered models that followed it, but I haven't needed to do that yet so I can't be specific.

The deal with these old Jonnys is to grab any parts saw you come across, no matter how trashed it appears to be. There's always something on there that you can use.

I believe that the piston and cylinder from the 50, 51, and 52 can be used on this saw. You will need each respective intake manifold though. The manifold from the 51 won't fit on the 50 or 52 or 49 so if you are buying a cylinder make sure you can get the proper intake. All of the above saws are 49cc. I have not done this personally so take it for what it is worth. I am in the process of doing this with my 51 so I can report back later.

The 49sp takes a standard 44mm x 1.5mm piston ring. They are widely available and like others have mentioned the 350 ring will work.

I think there are some differences in the coil mounting between the 49sp and the 52's that would make it complicated to use those cylinders on a 49sp. I have had good sucess using the 52's two ring piston in the 49sp but have never interchanged the cylinders. As I remember there was a change to an electronic ignition after the 49sp's.......Bob

Hmm,. thats new to me, I bought a 52 jug and slug to fix my 49, but now I see that its missing the entire ignition system. I think I am better off buying another 49 for parts and making a Frankensaw out of the two.

Originally Posted by Farley9n

I think there are some differences in the coil mounting between the 49sp and the 52's that would make it complicated to use those cylinders on a 49sp. I have had good sucess using the 52's two ring piston in the 49sp but have never interchanged the cylinders. As I remember there was a change to an electronic ignition after the 49sp's.......Bob

Yes the ignitions are different, but the piston and cylinders will fit. The 49's coil mounts on the cylinder while the later models mounted in the recoil if I remember right. You can put the p&c off the other models on the 49, but I guess you would need the entire ignition system from the 50 series saws. Might be more difficult than finding a 49sp piston and cylinder.