Jonsered621 suddenly died

[frankconley]

Well.....ebay is fickle...sometimes if you wait stuff will grow legs and be gone. You know you need a piston so if you get a piston and cyl together so much the better. I'd offer him $50 and see where that goes. You might be able to save your cyl but that is also a lot of work/time with no way to know if you will be successful until you get it cleaned up.....after spending all that time on it you might find it to be ruined. You just never know when buying from ebay......after you order a used one a NOS one may appear. What I do is just buy what I need to get the saw running again then if I find a rare bargain on a NOS piston and/or cyl I'll buy those and swap them out when time allows. That's one of the nice thing about working on saws......top end swap shouldn't take more than an hour or so if you have everything ready.........usually takes longer to clean a saw up enough to work on than to actually do the work!!

Here are pictures. Piston rings, cylinder wall, saw.

 

[frankconley]

Well.....ebay is fickle...sometimes if you wait stuff will grow legs and be gone. You know you need a piston so if you get a piston and cyl together so much the better. I'd offer him $50 and see where that goes. You might be able to save your cyl but that is also a lot of work/time with no way to know if you will be successful until you get it cleaned up.....after spending all that time on it you might find it to be ruined. You just never know when buying from ebay......after you order a used one a NOS one may appear. What I do is just buy what I need to get the saw running again then if I find a rare bargain on a NOS piston and/or cyl I'll buy those and swap them out when time allows. That's one of the nice thing about working on saws......top end swap shouldn't take more than an hour or so if you have everything ready.........usually takes longer to clean a saw up enough to work on than to actually do the work!!

Hi. I was able to get cylinder off. Here are new pics.

 

[Cantdog]

Wow. You are a godsend. You are probably sick of compliments. I just read your jonsered rebuild post. That's why I haven't sent pics yet. I was wondering if I could just pull cylinder and change piston and cylinder? Should I get rings and cylinder gasket kit I saw on ebay or use rings on replacement piston? Thanks.

Do

Wow. You are a godsend. You are probably sick of compliments. I just read your jonsered rebuild post. That's why I haven't sent pics yet. I was wondering if I could just pull cylinder and change piston and cylinder? Should I get rings and cylinder gasket kit I saw on ebay or use rings on replacement piston? Thanks.

Yes I would buy a good used P&C set like the one I posted. and buy a pair of new 45MM X 1.5MM Caber brand rings. But again I caution you that the reason this occurred needs to be found and remedied or this will happen again. If you have found a gasket set for the 621 on ebay you should acquire that as well....OEM kits should come with new crank seals if not suitable ones can be found at the local bearing supply house. Replacing the crank seals is a fair amount of work.....not really replacing the actual seals but the sprocket and clutch must be removed and on the other side the flywheel and complete ign system must be removed to expose the seal on that side. Simple rubber seals don't last dependably pas 20 years or so and yours are close to 40 years old.

 

[Cantdog]

Hi. I was able to get cylinder off. Here are new pics.View attachment 828700View attachment 828701

Notice how you con rod and counter weights look wet......this tells me you had sufficient oil in the mix......look back at my pics of the same area....dry as a bone....another thing that will kill a saw quickly is running a dull chain...this allows the motor to rev higher for longer periods. Your saw was in good shape, pretty low hour, very similar condition to the one I'm working on here. You can tell this by the visible, horizontal machine marks on the piston thrust faces (front and back)....a saw with many hours on it these wear away and the piston skirt is smooth and shiny
When you pulled the cyl did the cyl base gasket come off in one piece or was it broken?

 

[frankconley]

Notice how you con rod and counter weights look wet......this tells me you had sufficient oil in the mix......look back at my pics of the same area....dry as a bone....another thing that will kill a saw quickly is running a dull chain...this allows the motor to rev higher for longer periods. Your saw was in good shape, pretty low hour, very similar condition to the one I'm working on here. You can tell this by the visible, horizontal machine marks on the piston thrust faces (front and back)....a saw with many hours on it these wear away and the piston skirt is smooth and shiny
When you pulled the cyl did the cyl base gasket come off in one piece or was it broken?

https://www.ebay.com/itm/Jonsered-6...816642?hash=item3b027cff02:g:zKEAAOSwWY5ajyS4
This is the rings and gasket I was talking about. Could you look at it and see if it is like mine? I emailed the guy you gave me and asked about the piston, if it has 2 rings. I had high compression before it stopped running. I didn't find a rebuild kit only the rings and gasket kit so far. I'm afraid to ask why I should change the seals. Could it cause the piston to be damaged? I have the clutch removal tool you showed in the rebuild post. The top of the piston is carboned. Does that tell anything? Is it hard to get the piston pin out the way I have it with the rod still installed? Thanks for helping. Please write back when you feel like it. My gasket came off intact. My cylinder is discolored but feels smooth on the bad spot.

 

[Cantdog]

You have a serious amount of aluminum transfer on that cyl…..this can be removed with numerous applications of muriatic acid and scotchbrite. However the telling tale will be when you're done. Do a search on aluminum transfer removal. If once you have removed ALL the aluminum, drag your fingernail across the affected area...….if your nail catches on anything the cyl is useless. This will involve a substantial amount of time and elbow grease with no guarantee when you start that success will be yours.....much easier to just replace the whole thing in my humble opinion.
That gasket and ring set looks like it would work.....the rings are fine as they are cabers.....the gasket looks pretty thick. OEM ones are about 0.010" thick and compress to around 0.007" when tightened down. A thicker gasket than stated will drop compression a bit.

 

[frankconley]

You have a serious amount of aluminum transfer on that cyl…..this can be removed with numerous applications of muriatic acid and scotchbrite. However the telling tale will be when you're done. Do a search on aluminum transfer removal. If once you have removed ALL the aluminum, drag your fingernail across the affected area...….if your nail catches on anything the cyl is useless. This will involve a substantial amount of time and elbow grease with no guarantee when you start that success will be yours.....much easier to just replace the whole thing in my humble opinion.
That gasket and ring set looks like it would work.....the rings are fine as they are cabers.....the gasket looks pretty thick. OEM ones are about 0.010" thick and compress to around 0.007" when tightened down. A thicker gasket than stated will drop compression a bit.

Hi. Thanks for writing
This is my before picture. I hope it works. I will probably buy the p&c on ebay if the guy writes back. I will pour muratic acid on my cylinder to see if it fizzes up. Is a new gasket better than reusing my old one? The second picture is my vacuum made from my hair dryer. It works pretty good.

 

[frankconley]

You have a serious amount of aluminum transfer on that cyl…..this can be removed with numerous applications of muriatic acid and scotchbrite. However the telling tale will be when you're done. Do a search on aluminum transfer removal. If once you have removed ALL the aluminum, drag your fingernail across the affected area...….if your nail catches on anything the cyl is useless. This will involve a substantial amount of time and elbow grease with no guarantee when you start that success will be yours.....much easier to just replace the whole thing in my humble opinion.
That gasket and ring set looks like it would work.....the rings are fine as they are cabers.....the gasket looks pretty thick. OEM ones are about 0.010" thick and compress to around 0.007" when tightened down. A thicker gasket than stated will drop compression a bit.

It worked. About 1 16th side to side wobble in connecting rod

 

[Jasonrkba]

40.1 is fine. I'd try and restore the cylinder and replace the piston. Replace the seals as said above. Make sure there is no leaks around the intake area.

 

[Cantdog]

Side to side play in the big end bearing is fine.....ANY up and down play is not.....I'm guessing you're fine.
Notice the thrush washers on either end of your wristpin....these keep the lower end of the conrod centered on the crankpin.
Hopefully he'll get back to you today on that P&C set. Ordinarily I would try salvage your cyl…..but you still need a piston and these are not readily available so if you can pick up both in good used condition for a decent price you can speed this along and save yourself a lot of grief. I have cleaned many cyls like yours....sometimes you can sometimes save them sometimes you can't.....and generally you won't know either way until you've done all the labor. Don't remember even once when the doing of it was all that pleasant. If your cyl base gasket is intact and looks to be in good condition I wouldn't hesitate to reuse it if I didn't have an OEM one. If it has cracks or very thin spots I would not. That's an OK price in that gasket/ring set....I pay $4.50 each for Caber rings but if that's all I buy and there is a $7.00 shipping fee I'm up to $16.00 so $4.00 for a gasket and I'm right there...so I'd go with it.
Make sure to save the wristpin keepers from your old piston.....a used piston may or may not arrive with both.....

 

[frankconley]

40.1 is fine. I'd try and restore the cylinder and replace the piston. Replace the seals as said above. Make sure there is no leaks around the intake area.

Thanks for responding. What is intake area? Carb gasket? Here is picture of little pin, nub like bump where bar chain oil was found around it. It is above oil cap area. Do you know what it is?

 

[frankconley]

Side to side play in the big end bearing is fine.....ANY up and down play is not.....I'm guessing you're fine.
Notice the thrush washers on either end of your wristpin....these keep the lower end of the conrod centered on the crankpin.
Hopefully he'll get back to you today on that P&C set. Ordinarily I would try salvage your cyl…..but you still need a piston and these are not readily available so if you can pick up both in good used condition for a decent price you can speed this along and save yourself a lot of grief. I have cleaned many cyls like yours....sometimes you can sometimes save them sometimes you can't.....and generally you won't know either way until you've done all the labor. Don't remember even once when the doing of it was all that pleasant. If your cyl base gasket is intact and looks to be in good condition I wouldn't hesitate to reuse it if I didn't have an OEM one. If it has cracks or very thin spots I would not. That's an OK price in that gasket/ring set....I pay $4.50 each for Caber rings but if that's all I buy and there is a $7.00 shipping fee I'm up to $16.00 so $4.00 for a gasket and I'm right there...so I'd go with it.
Make sure to save the wristpin keepers from your old piston.....a used piston may or may not arrive with both.....

Do you know what this nub above oil fill area is?

Thanks for the good info. The guy wrote back but he is busy moving. Hopefully he'll write again soon.

 

[frankconley]

Thanks for responding. What is intake area? Carb gasket? Here is picture of little pin, nub like bump where bar chain oil was found around it. It is above oil cap area. Do you know what it is?

40.1 is fine. I'd try and restore the cylinder and replace the piston. Replace the seals as said above. Make sure there is no leaks around the intake area.

 

[Cantdog]

That is called a "wiggle pin". It is actual a tiny brass cotter pin and should be lose to move about a tiny bit. This is your oil tank vent to allow air in as bar oil is used

 

[frankconley]

That is called a "wiggle pin". It is actual a tiny brass cotter pin and should be lose to move about a tiny bit. This is your oil tank vent to allow air in as bar oil is used
[/QUOTE
Hi. Thanks for the good information. I can see the top of a cotter pin now that the sun is shining and it is brighter in my house. This is a piston on eBay. I emailed the seller and told him my piston has 2 rings and he said his will work. The part number he lists is for the rings on my saw. That is a little sketchy. Do you have any ideas about it?
https://www.ebay.com/itm/JONSERED-6...e&pageci=27b39af9-0a06-4afd-86cc-083984af0d13

 

[Cantdog]

Yeah that's a cheap China or India piston...likely China. Just because it's 45mm doesn't make it correct... And that is not a 621 piston...it actually fits a 590 Jonsered. It might fit but it's a flat top piston with windows and single ring. Your 621 piston has no windows, two rings and is a high compression domed piston. I would pass on that......and of course you don't know if your cyl will clean up or not. I'd stay in touch with the guy I posted earlier or wait for another set to come along......You won't be happy if you want the saw repair to last by jambing inferior parts into it. Patience is key.

 

[frankconley]

Yeah that's a cheap China or India piston...likely China. Just because it's 45mm doesn't make it correct... And that is not a 621 piston...it actually fits a 590 Jonsered. It might fit but it's a flat top piston with windows and single ring. Your 621 piston has no windows, two rings and is a high compression domed piston. I would pass on that......and of course you don't know if your cyl will clean up or not. I'd stay in touch with the guy I posted earlier or wait for another set to come along......You won't be happy if you want the saw repair to last by jambing inferior parts into it. Patience is key.

Thanks. I agree. It was just on case the other guys piston was bad I was looking for a back up.

 

[frankconley]

Yeah that's a cheap China or India piston...likely China. Just because it's 45mm doesn't make it correct... And that is not a 621 piston...it actually fits a 590 Jonsered. It might fit but it's a flat top piston with windows and single ring. Your 621 piston has no windows, two rings and is a high compression domed piston. I would pass on that......and of course you don't know if your cyl will clean up or not. I'd stay in touch with the guy I posted earlier or wait for another set to come along......You won't be happy if you want the saw repair to last by jambing inferior parts into it. Patience is key.

Is it true a vacuum check can damage your diaphragm?

 

[Cantdog]

Is it true a vacuum check can damage your diaphragm?

Do you mean the diaphragm in the carb?

 

[rupedoggy]

Hey cantdog are there other diaphragms on saws? Mike