Jonsered621 suddenly died

[Cantdog]

Hey cantdog are there other diaphragms on saws? Mike

Sometimes ya have to ask the tuff questions.....

 

[frankconley]

Do you mean the diaphragm in the carb?

Yes. The diaphragm in the carb. Thanks for writing back. I'm excited about getting my saw fixed. I feel bad for screwing it up. I used oldish gas and the cheapest walmart oil that was sitting in a half used container outside all winter and the wrong mixture then I worked it real hard cutting 17 inch logs with a 16 inch blade. That good old saw deserved better. I want to make it right.

 

[Cantdog]

Yes. The diaphragm in the carb. Thanks for writing back. I'm excited about getting my saw fixed. I feel bad for screwing it up. I used oldish gas and the cheapest walmart oil that was sitting in a half used container outside all winter and the wrong mixture then I worked it real hard cutting 17 inch logs with a 16 inch blade. That good old saw deserved better. I want to make it right.

When you do a pressure/vac test you block off the muffler and carb from the p&c and crankcase. Some folks make special plates for this others make rubber gaskets from an old inner tube and simply sandwich them between the intake and exhaust ports by bolting the muffler and carb back on with the gaskets between. I use a piston stop that screws into the sparkplug hole and has a hose connection to attach the vac/pressure pump to. The carb is not subject to any pressure or vac so the diaphragm is safe.
Yep.....sorry about your saw......the guy here feels the same way about straight gassing his 621. I grew up on an off shore island and have used outboards since I was 7-8 years old. Oil was way different back then and my old man was a "more oil is better" kinda guy so I was too......and have been most of my life.
But since I started working on saws a lot I've gone 100% the other way as I've seen many saws die of carbon poisoning or like yours, scoring. I'm not a Stihl flag waver but I do use Stihl Ultra exclusively because it is very hi detergent, full synthetic and it's always on the shelf locally. As you now are seeing there's no savings to cheap oil.

 

[frankconley]

Do you mean the diaphragm in the carb?

Hi again. This is the piston. I may buy the other parts but shipping may be too high.

 

[frankconley]

When you do a pressure/vac test you block off the muffler and carb from the p&c and crankcase. Some folks make special plates for this others make rubber gaskets from an old inner tube and simply sandwich them between the intake and exhaust ports by bolting the muffler and carb back on with the gaskets between. I use a piston stop that screws into the sparkplug hole and has a hose connection to attach the vac/pressure pump to. The carb is not subject to any pressure or vac so the diaphragm is safe.
Yep.....sorry about your saw......the guy here feels the same way about straight gassing his 621. I grew up on an off shore island and have used outboards since I was 7-8 years old. Oil was way different back then and my old man was a "more oil is better" kinda guy so I was too......and have been most of my life.
But since I started working on saws a lot I've gone 100% the other way as I've seen many saws die of carbon poisoning or like yours, scoring. I'm not a Stihl flag waver but I do use Stihl Ultra exclusively because it is very hi detergent, full synthetic and it's always on the shelf locally. As you now are seeing there's no savings to cheap oil.

Yep that oil is on my list. Thanks for the testing info. I should have figured that out. I bought the stuff in the pictures plus the cylinder for 70 dollars plus 23 shipping. Maybe those points are good. Thanks for the heads up.

 

[Cantdog]

Yep that oil is on my list. Thanks for the testing info. I should have figured that out. I bought the stuff in the pictures plus the cylinder for 70 dollars plus 23 shipping. Maybe those points are good. Thanks for the heads up.

Well that's not to bad price.....a lot.... but if you needed any other parts and had to buy them one at a time you would likely spend all of that and more. Parts is parts.....there's a lot there. I expect the clutch is still on the other side, you've got an extra trigger handle an AV mounts, gas and oil caps, it looks like you have the two upper top handle AV mounts as well (if they are nor broken)…..and though it seems like nothing....that little brass cotter pin on the choke shaft is very hard to come by....and of course the entire points plate, condenser and coil....tank vent and fuel line junction block and carb etc. That fuel line is very special and near impossible to find NOS. If it is pliable with no cracks hide that away for safe keeping.....it's one size on one end and a totally different size on the other. Crankshaft and oil pump too. You may never need most of these parts but it seems you want to bring this saw back to be able to use dependably and every part there is NLA and every year will become harder and harder to find....especially the rubber bits..

 

[frankconley]

Well that's not to bad price.....a lot.... but if you needed any other parts and had to buy them one at a time you would likely spend all of that and more. Parts is parts.....there's a lot there. I expect the clutch is still on the other side, you've got an extra trigger handle an AV mounts, gas and oil caps, it looks like you have the two upper top handle AV mounts as well (if they are nor broken)…..and though it seems like nothing....that little brass cotter pin on the choke shaft is very hard to come by....and of course the entire points plate, condenser and coil....tank vent and fuel line junction block and carb etc. That fuel line is very special and near impossible to find NOS. If it is pliable with no cracks hide that away for safe keeping.....it's one size on one end and a totally different size on the other. Crankshaft and oil pump too. You may never need most of these parts but it seems you want to bring this saw back to be able to use dependably and every part there is NLA and every year will become harder and harder to find....especially the rubber bits..

Wow. Thanks for the good info. If you ever need a part I will send it to you.

 

[frankconley]

Well that's not to bad price.....a lot.... but if you needed any other parts and had to buy them one at a time you would likely spend all of that and more. Parts is parts.....there's a lot there. I expect the clutch is still on the other side, you've got an extra trigger handle an AV mounts, gas and oil caps, it looks like you have the two upper top handle AV mounts as well (if they are nor broken)…..and though it seems like nothing....that little brass cotter pin on the choke shaft is very hard to come by....and of course the entire points plate, condenser and coil....tank vent and fuel line junction block and carb etc. That fuel line is very special and near impossible to find NOS. If it is pliable with no cracks hide that away for safe keeping.....it's one size on one end and a totally different size on the other. Crankshaft and oil pump too. You may never need most of these parts but it seems you want to bring this saw back to be able to use dependably and every part there is NLA and every year will become harder and harder to find....especially the rubber bits..

If you have time could you look at these and tell me if either are a bargain?
https://www.ebay.com/itm/Jonsereds-...3ef-2db6-4b87-9ac8-04700668b803&epid=77587922

https://www.ebay.com/itm/Jonsereds-621/164200705588?hash=item263b1fee34:g:h7YAAOSwqOBevpwN

 

[Cantdog]

I've read both those adds earlier and believe both have issues and are overpriced once you add the $60 shipping.... but that's ebay for you. The second one has fair potential but the case is broken where the spikes bolt on.....not a deal breaker perhaps but it does devalue the saw. The first is simply way over priced....neither saw has what I would call excellent compression numbers for a 621. As I said earlier 621 in good condition should blow over 200 lbs all day long. Ebay sometimes is ok to get parts from but if some has one of these old obsolete saws, that you can't a single new part for except a spark plug and recoil spring, that's nearly intact they think they have a gold mine. I love the 621s but one would have to really impress me for me to pay $150 delivered to my door. Like the 49Sp they made and sold a million 621's and they were great saws and lasted very well so there are thousands of them still sitting under someone's bench collecting dust.

 

[frankconley]

I've read both those adds earlier and believe both have issues and are overpriced once you add the $60 shipping.... but that's ebay for you. The second one has fair potential but the case is broken where the spikes bolt on.....not a deal breaker perhaps but it does devalue the saw. The first is simply way over priced....neither saw has what I would call excellent compression numbers for a 621. As I said earlier 621 in good condition should blow over 200 lbs all day long. Ebay sometimes is ok to get parts from but if some has one of these old obsolete saws, that you can't a single new part for except a spark plug and recoil spring, that's nearly intact they think they have a gold mine. I love the 621s but one would have to really impress me for me to pay $150 delivered to my door. Like the 49Sp they made and sold a million 621's and they were great saws and lasted very well so there are thousands of them still sitting under someone's bench collecting dust.

Thanks for writing. I agree the compression is not good for that saw. 60 shipping is weird too. To me. Different subject. Can I use a nut and bolt to pull my wrist pin through my piston to reinstall? With nylon washer on each end to prevent damage. Or pound it through with wood block and hammer with wood backing up the other side?
Also I'm hesitating to change my crankshaft seals but I would like to find some just in case. Do you know a source?

Do you have a way to find a 621 that I can use in my area? Like garage sales or shows or whatever.

 

[frankconley]

I've read both those adds earlier and believe both have issues and are overpriced once you add the $60 shipping.... but that's ebay for you. The second one has fair potential but the case is broken where the spikes bolt on.....not a deal breaker perhaps but it does devalue the saw. The first is simply way over priced....neither saw has what I would call excellent compression numbers for a 621. As I said earlier 621 in good condition should blow over 200 lbs all day long. Ebay sometimes is ok to get parts from but if some has one of these old obsolete saws, that you can't a single new part for except a spark plug and recoil spring, that's nearly intact they think they have a gold mine. I love the 621s but one would have to really impress me for me to pay $150 delivered to my door. Like the 49Sp they made and sold a million 621's and they were great saws and lasted very well so there are thousands of them still sitting under someone's bench collecting dust.

This is a picture of my oil vent. Oil seeps out while it just sitting there. Even drained onto counter top. Is this normal? The reservoir is not full.

 

[Cantdog]

Thanks for writing. I agree the compression is not good for that saw. 60 shipping is weird too. To me. Different subject. Can I use a nut and bolt to pull my wrist pin through my piston to reinstall? With nylon washer on each end to prevent damage. Or pound it through with wood block and hammer with wood backing up the other side?
Also I'm hesitating to change my crankshaft seals but I would like to find some just in case. Do you know a source?

Do you have a way to find a 621 that I can use in my area? Like garage sales or shows or whatever.

As I previously said....you need to find out why this happened definitively......it could have been old gas, crappy oil, over worked, dull chain and any combination there of. However if you do have a leaking crank seal you'll be looking for another P&C before long. 40 years or so is a lot to ask from a rubber seal...they get hard and just plain leak. There are only two ways I know of to eliminate the possibility....one is to do a thorough pressure/vac test which can be expensive if you don't already own a Mity Vac and somewhat time consuming......or just bite the bullet and change them out. It is somewhat painful to come up with the pullers you'll need to pull the flywheel and the clutch spyder but once done changing the seals is easy. I can't post from here as they are on another drive but will when I get home for lunch.....I'll send a pic of the ones I use if I don't have OEM ones.

As far as putting the wristpin back in....it may just slide in with your thumbs...if not toss just the piston in a toaster over for 15 mins at 225 degrees...should slide right in then. Remember to clean the piston crown completely of any carbon...you'll notice an arrow on the top that should point to the exhaust port and puts both ring ends toward the back of the saw. Also take one of the old rings and snap it off mid way or so and use that to carefully scrape the ring grooves clean of all carbon.....do not scrape off the aluminum just the carbon.

Yep yard sales, craigslist or similar, flea markets and place like that to find old saw for sale.

 

[Cantdog]

These are the seals I use if I happen to not have OEM ones in stock. They are 1 MM deeper/thicker at 7mm than OEM 6mm ones but work fine...they should be installed just flush with the case. You can use these part numbers to cross reference to a different brand if necessary. Any quality bearing supply house will have these.

 

[Cantdog]

This is a picture of my oil vent. Oil seeps out while it just sitting there. Even drained onto counter top. Is this normal? The reservoir is not full.View attachment 829829

I can think of no reason why bar oil would defy gravity and climb up out of the tank if the level is below the vent...not normal..

 

[sundance]

These are the seals I use if I happen to not have OEM ones in stock. They are 1 MM deeper/thicker at 7mm than OEM 6mm ones but work fine...they should be installed just flush with the case. You can use these part numbers to cross reference to a different brand if necessary. Any quality bearing supply house will have these.

View attachment 829840

@Cantdog - What sealant do you use on these seals?
Thanks

 

[frankconley]

I can think of no reason why bar oil would defy gravity and climb up out of the tank if the level is below the vent...not normal..

Hi. After sitting undisturbed all day my chainsaw had a puddle of chain oil under it. It was 80 degrees today and that's the warmest it's been since I set it there. Not coming out of vent hole this time. Is that normal? Different subject. Is chain oil quality important?

 

[frankconley]

I can think of no reason why bar oil would defy gravity and climb up out of the tank if the level is below the vent...not normal..

I think I had my oil cap crossthreaded. What a jerk. Sorry.

 

[Cantdog]

@Cantdog - What sealant do you use on these seals?
Thanks

I don't use any sealer on the seals....generally just a light film of white lithium grease around the outside and on the lips of the seal itself. OEM seals are bare metal on the outside. The TCM seals are metal as well but are also nitrile coated around the outside so sealing is not an issue.

 

[Cantdog]

I think I had my oil cap crossthreaded. What a jerk. Sorry.

LOL!! You almost had me thinking your 621 was possessed!!!

 

[Bobby Kirbos]

While you're at it, for the price, replace the decomp. I just replaced the top end on a Stihl 660 that had similar damage to the piston. The saw wouldn't stay running. After tearing into it, I found that the decomp was shot. It had zero "pop" to its movement. I suspect that the bad decomp was leaking which not only killed compression but the leaked air was leaning out the mixture and created a hot spot on the piston.