NEW 49SP AM Pistions!!!!!!!!!!

[Cantdog]

I saw one advertised on E-Bay from a seller (whose name cannot be spoken) last Monday and I asked where they were made..got a quick answer.. India....asked if they had the same crown as the original...another quick reply..yes exactly the same as the original..Hmmmm OK I can't resist so I order one Monday evening..it arrived yesterday. I imediately set about measuring and comparing, checking specs etc. It measured just perfect, pin height correct, crown shape and height correct, stout firm circlips, ring lands just right....it is a good looking piston...not as smooth a casting inside as a Mahle but I never expected it be. This is great (well, atleast for all the 49sp owners!!) as there has never been an AM piston available for these. This is all good....but now comes the one issue I discovered with these and some may well dissagree with me on this whether it's even a problem or not....but for me, however, it is. When I measured the distance between the wristpin bosses I got .510"....a 49/52 conrod top measures .393" for a running crearance of .117". So I measure a Mahle 49sp piston and get .437" which gives a running clearance of .044" and this is sloppy by most standards I find, as I measure other motors apart at the shop. Here is a sampling 52E .021", 262XP .012", 272XP .010" Now, how tight upper rod end and the piston are dictates how the lower con rod end is held in center on the crankpin and bearing. There is always quite a bit of side play in the lower bearing but the ability of the rod to slide back and forth is limited (or should be) by the upper end fit. This was kind of a bummer to find on an otherwise pretty darn nice AM piston. However this can easily be overcome. What I have decided to do is fit a set of 52E thrust washers to my 49 bearing. This is a bit to fat to fit between the bosses so I will have to mill off around .033" off each boss to achieve a running clearance of .012". Not a biggie...as I have a number of 52/52E thrust washer sets...and after yrs of scrounging used pistons that were not to worn to use, just having one that fits the bore properly is awsome!!!! These could be used in the 52/52E as well but they are single ring as opposed to two.

 

[Cantdog]

LOLOL!!! How do you like those PISTIONS????? Cussed edit wouldn't let me change it!! LOLOL!!!

 

[kr5258]

Thanks for the info! Here's your pics:

 

[PB]

Thanks Robin! That is good to know! Those pistons will give many saws a second, third or fourth life. I wonder if there is a variation from one piston to the next with the pin boss clearances.

 

[Cantdog]

Thanks Robin! That is good to know! Those pistons will give many saws a second, third or fourth life. I wonder if there is a variation from one piston to the next with the pin boss clearances.

I expect there is, as the surface of the bosses is cast. The ebayer I got this one from was very nice and forthcoming and expainled the Northwoods had these developed. I sent an email to them congradulating and thanking them for their efforts but also pointing out this issue.

 

[Cantdog]

A couple more pics... one showing the circlips..the one one the right is stock...the one on the left came with this piston. The other pic is the thrust washers from a 52 and a 49sp bearing..the big bearing if from a 70E and has nothing to do with the rest of this.

 

[lfnh]

Thanks Cantdog for the research on these AM pistons. Just the ticket.
It would nice to see the clearance between bosses tightended up some more.
How does a factory 49sp ring fit up into the new piston ?

 

[Dan_IN_MN]

A couple more pics... one showing the circlips..the one one the right is stock...the one on the left came with this piston. The other pic is the thrust washers from a 52 and a 49sp bearing..the big bearing if from a 70E and has nothing to do with the rest of this.

Were these pistons made specifically for the Jonsereds 49sp?

 

[Cantdog]

Were these pistons made specifically for the Jonsereds 49sp?

Yes

 

[Cantdog]

Thanks Cantdog for the research on these AM pistons. Just the ticket.
It would nice to see the clearance between bosses tightended up some more.
How does a factory 49sp ring fit up into the new piston ?

I don't know for sure..haven't got that far yet but I believe they are just the standard 1.5MM rings..

 

[Cantdog]

Thanks Cantdog for the research on these AM pistons. Just the ticket.
It would nice to see the clearance between bosses tightended up some more.
How does a factory 49sp ring fit up into the new piston ?

Just a followup on this question..the ring supplied with the piston fit very well in the groove...nice and snug but not tight. I plan to talk again with Northwoods and find out if the supplied ring is a Caber. If it isn't (and they are 1.5MM) I'll either use a new Caber or NOS 44MM ring from Jonsereds.

When I get time I plan to throw together another 49SP to test this piston in....just to see if I can overwork it.....check wear patterns after 15-20 cord of 16" fitted hardwood etc. I am very optimistic about these pistons. I was told that Northwoods had plenty of these available and they do now list them on their website. It great to see a site sponsor care enough to put up the time and capital to actually create an item that has been needed for such a long time. Bravo Northwoods!!! Many of these nice little saws have been trashed just for need of a piston. ( I have a few!!) As I said earlier too, these can also breath new life into 52/52E line as well. The 49sp piston were not as robust overall, nor the crown quite as high as the 2 ring 52/52E pistons but should work fine none the less as I have two 49SPs with 52 pistons installed and they run great.

 

[SkippyKtm]

I just sent them a message to see if they would make the Husqvarna 44mm 55 Rancher EPA piston. I'll bet if they did, they would sell 'em like hotcakes...

 

[taplinhill]

Hey Robin, nice write-up.
It's scarry to think how many running 49SP's you could end up with!

 

[Cantdog]

Hey Robin, nice write-up.
It's scarry to think how many running 49SP's you could end up with!

LOL Yes it is eric.......I may have to change my sig to "Not As Many 49SP Parts Saws" LOL!!!!

 

[hotshot]

When I measured the distance between the wristpin bosses I got .510"....a 49/52 conrod top measures .393" for a running crearance of .117". So I measure a Mahle 49sp piston and get .437" which gives a running clearance of .044" and this is sloppy by most standards I find, as I measure other motors apart at the shop. Here is a sampling 52E .021", 262XP .012", 272XP .010" Now, how tight upper rod end and the piston are dictates how the lower con rod end is held in center on the crankpin and bearing. There is always quite a bit of side play in the lower bearing but the ability of the rod to slide back and forth is limited (or should be) by the upper end fit. This was kind of a bummer to find on an otherwise pretty darn nice AM piston. However this can easily be overcome. What I have decided to do is fit a set of 52E thrust washers to my 49 bearing. This is a bit to fat to fit between the bosses so I will have to mill off around .033" off each boss to achieve a running clearance of .012". Not a biggie...as I have a number of 52/52E thrust washer sets...and after yrs of scrounging used pistons that were not to worn to use, just having one that fits the bore properly is awsome!!!! These could be used in the 52/52E as well but they are single ring as opposed to two.

This is exactly why I returned a 56mm Magnum 056 piston in another thread last year... was not even machined flat inside & left in an "as cast" too wide condition. A short cut in the cheapened India IAP production. There's no way that piston design would keep the rod centered, but apparently the uneducated accept it, as BARRYDM's sold a lot of them. I looked for two weeks for thin 13mm ID shim washers, but could not find anything in that size. Wiseco pistons skipped the 13mm range. The Canadian parts seller banned me from purchasing anything else, as a reward for returning it.

 

[Cantdog]

This is exactly why I returned a 56mm Magnum 056 piston in another thread last year... was not even machined flat inside & left in an "as cast" too wide condition. A short cut in the cheapened India IAP production. There's no way that piston design would keep the rod centered, but apparently the uneducated accept it, as he's sold a lot of them. I looked for two weeks for thin 13mm ID shim washers, but could not find anything in that size. Wiseco pistons skipped the 13mm range. The Canadian parts seller banned me from purchasing anything else, as a reward for returning it.

This does seem to be the case with the cheaper AM pistons. I recently picked up a real sweet looking, little used 261 Husky with the idea of upgrading the piston with a 262 Meteor and porting it. When i pulled the muffler off I noticed it already had a flat top that was shiney and new??? When I pulled the jug off the piston and rod seemed to be way loose and floppy!!!! I first thought the big end had gone south but as I inspected I found the big end to be fine but the piston was extreamly loose side to side. Pulled that and it was made by Golf and had similar side play in the .125" range. Totally unacceptable for a high performance saw. I measured a worn out stock 262XP piston and upper end con rod and found it to have .012" running clearance after being worn out!! This problem may account for a number of AM piston failures that has previously gone undetected.

 

[spike60]

That's pretty good news. But I'm still not gonna catch up to you.

Now what I'd really like to see is an aftermarket coil. One of mine is mint, but the coil fried.

 

[Cantdog]

That's pretty good news. But I'm still not gonna catch up to you.

Now what I'd really like to see is an aftermarket coil. One of mine is mint, but the coil fried.

Do you need a 49SP coil Bob??? I can get one out to you the first of the week..no problem.

 

[Cantdog]

Another update on the ring.....they are 1.5MM same as stock. I took a NOS 44MM X1.5MM and installed it in the bore of as used but in good shape cyl and checked the end gap...it was .006" then I did the same with the ring supplied supplied with the piston the end gap also measured .006" and this ring seemed every bit as well made and supplied about the same tension when compressed as did the stock Jonsereds ring....I will more than likely use the ring supplied when I install the piston.....so again the only fault I can find so far is the excessive (IMHO) rod to wristpin boss clearance. which, though I shouldn't have to, I can deal with quickly and effectively.

Again... to the crew at Northwoods!!!

 

[lfnh]

Cantdog - Thanks for the time to check the ring. Numbers look good. Thanks Northwoods!