Rescuing a Jonsered 2051 cutting up pistons also works for closed port 55s

[Uzi]

I came across a nice 2051 that was seized but pretty complete only missing the plastic cover on the sides of the rear handle. I got it apart last night and the bottom is good everything else is in order and the cylinder cleaned up well.
Any ideas where to find a piston for it? It's a windowed one that reminds me of the style that was in a closed port 55 that is also impossible to get. I had the same problem with that saw and ended up dremeling windows in a piston to keep the closed port cylinder on that saw. It turned out to be a screamer and I'm hoping for the same with this one. Has anyone used a piston from husqvarna or something similar that works in this saw?

 

[Seedling345]

You might try tractor supply the one here in Howell sells jonsered saws and parts


I once knew a guy who knew a guy

 

[Seedling345]

Any luck???


I once knew a guy who knew a guy

 

[Uzi]

Well sort of I tore down my closed port 55 which also has a 45mm piston turns out the Pistons are identical as far as I can tell. Same wrist pin and bearing size same windows and everything that the closed port 55 had. So I'm going to order another piston for a 51 that is 45 mm like I did with the 55, regular open port 55 Pistons are 46mm.

Then I will take the dremel to it and cut windows in the side like I did with the other one. It doesn't look real pretty and when I did a thread about the 55 and cutting the piston many people here thought it would come apart violently because of the no name piston high RPMs and increased compression, I deleted the base gasket while I was doing the rebuild. I have no idea what it runs for RPMs but it's high and I've put gallons of fuel though it and it still looks great. It's become my go to small saw really like how it runs. I will try to post up here I get it done and take some pictures.

Here a link to the other thread if you're interested http://www.arboristsite.com/communi...-repaired-piston-cut-and-photos-added.249658/

 

[Seedling345]

Ahh I'm no mechanic I just know the tsc by my house sells actual parts for jonsered figured ode throw it out there


I once knew a guy who knew a guy

 

[zogger]

Well sort of I tore down my closed port 55 which also has a 45mm piston turns out the Pistons are identical as far as I can tell. Same wrist pin and bearing size same windows and everything that the closed port 55 had. So I'm going to order another piston for a 51 that is 45 mm like I did with the 55, regular open port 55 Pistons are 46mm.

Then I will take the dremel to it and cut windows in the side like I did with the other one. It doesn't look real pretty and when I did a thread about the 55 and cutting the piston many people here thought it would come apart violently because of the no name piston high RPMs and increased compression, I deleted the base gasket while I was doing the rebuild. I have no idea what it runs for RPMs but it's high and I've put gallons of fuel though it and it still looks great. It's become my go to small saw really like how it runs. I will try to post up here I get it done and take some pictures.

Here a link to the other thread if you're interested http://www.arboristsite.com/communi...-repaired-piston-cut-and-photos-added.249658/

Good luck! It's cool when you can make something work with other than normal stock parts.

 

[Uzi]

Update on this I finally got the no-name pistons I wanted last night. I know they do make a 45mm meteor piston without windows but I didn't want one of those to carve up because of casting thickness. I don't know what the casting looks like on those but these cheap Chinese pistons are so thick it makes a great choice to start carving on. There is more meat in the wrist pin area than the stock piston by a huge amount.

There's also a disadvantage to them they are not exactly made to specs like the factory Mahle piston was. I ended up with 2 of the no name pistons because the first one shipped with no circlips (I probably won't use them anyways) and a 46mm ring instead of 45mm. When I complained they sent another it had circlips but still came with a 46mm ring . I ordered 45mm Cabers figured they would be better quality anyways. I also measured them up last night and while the bore size is fine compared to stock, the overall height is shorter about 0.4mm. Obviously they are worried about squish clearance being to tight, both pistons measure within .1mm of each other so at least they are consistently bad. The 2051 has a really thick base gasket so it will be interesting to see where the final squish and compression ends up on my ported 55 it was around 160 psi minus the gasket with the cheap china ring. I may go back and put a caber in that one too just to see if there is a difference.

Here is some before and after pictures of the pistons I broke out the nice camera and macro setup to hopefully show better the difference in height between stock. Also to give better quality photos than the ones in the 55 thread I took with my cell phone.

 

[dsell]

I can see the overall height is different as is the crown, but what about the distance on each from the wrist pin to the top? Isn't that what will make the difference on your squish? I modified a 246 Golf piston to fit my Partner 5000 Plus cylinder bolted to a Husky 50 case. After I did that, nmurph showed me an aftermarket piston to fit it. http://www.arboristsite.com/community/threads/partner-5000-plus-aftermarket-piston.250381/page-2 Maybe that would work for you.


Never mind, that's a 44mm piston.

 

[Uzi]

If the crown looks different it's just a camera trick they are both flat top Pistons. As far as the pin location everything is identical to the stock piston. I stuck a pin through both of them to line up the windows and trace them on the new piston. Everything lined up perfect it's just that the Chinese piston has 0.4mm less above the ring land.

 

[rmh3481]

Nice job on the full circle piston windows Uzi. Smaller windows close to the crown will generate higher velocities through those closed transfers.

In your second pic, the piston on the left we always called a 'slipper' piston with the one on the right known as 'full circle'. The slipper piston will run a closed port transfer 2T engine irregardless of whether there are windows in the piston or not, because of the gap over the transfers.

When shopping for pistons, match the diameter, wristpin size and compression height (measured from top of pin to edge of crown). This is essentially what guys are doing when they put an 064 piston into a big bore 372. Both pistons are the same diameter but the 064 piston has a slightly higher compression height.

Here is a link to Meteors catalog which lists style, wrist pin and compression heights for their pistons-
http://www.meteorpiston.com/Lists/G...c&View={CE32560A-49BF-47F8-9CFA-E52252EADD4C}

 

[Uzi]

Well this 2051 is alive and got a real workout this weekend. We did some line clearance work and it felled and limbed at least 50 12-14" cedars. My wife ran it most of the day but the few times I picked it up I was impressed especially after a couple tanks of fuel. Compression was around 175 psi cold before breaking in will have to get a gauge on it now and see where its at. These have a 2mm thick plastic base gasket and removing it will actually make the pistion hit the top of the cylinder. Even with a 0.6mm base gasket there was 0 squish clearance so I sanded down the original plastic one to around 1 mm could have probably went a little less and I might if I need to pull it apart again.

I raised the exhaust and transfers back up to stock height, added some bridge ports, a muffler mod and its really screaming. I don't know what its turning for RPM but it feels/sounds awesome and runs harder than my closed port 55 (which is has no base gasket and bridge ports too) and seems to hold more RPM in the cut. Might try to get a video at some point.

 

[dsell]

That's a thick base gasket. The best part is getting your wife to run it! Mine always finds something else to do when it's time to cut wood.