Jonsered Chainsaws

[ErnieG]

Yep I saw that earlier......not a bad BIN for something like that on ebay these daze.....filter looks like it might have come from a concrete saw maybe......?

I thought the same on both also ....

Ernie

 

[Real1shepherd]

I have not. I will tomorrow when I get home from work.

Tilly carbs have to have the top and bottom 'sandwiches' put in correctly and they are not in the same order. Makes sure the fuel diaphragm on the bottom is hooked into the little fork. If you have good blue spark and you're sure the carb is 100%.....make sure it's timed correctly.

Not the best compression but it should start and run. Never worked on that saw....solid state ignition.....not sure what provision to adjust timing.

You gotta find that leak though if it didn't pass a pressure/vac test. Even if you got the saw started, with an air leak you could run too lean and potentially damage the P&C.

Kevin

 

[Real1shepherd]

I agree.....run it like you're gonna run it........ don't baby it....don't beat on it....but will add that after a couple heat cycles I check the cyl base bolts, carb and muffler bolts as well, especially when using new gaskets....things may or may not get lose with use.

I do that with anything new or rebuilt....you can expect to retighten most things.

Kevin

 

[Real1shepherd]

I did, just as you guys instructed to do. After posting earlier about it not starting I pressure tested and I couldn't get it to hold. I can't figure out where the leak is though, I soap sprayed all the gaskets and the clutch side seal and didn't see bubbles.

I'm planning on disassembling and reassembling to make sure I didn't make any mistakes along the way.

As an aside, I want to make sure I got the tank vent correct. I tried to recreate the vent tube exactly how it came out of the factory, sintered brass filter and all. I got the filter in the tube, but I have a question about a one way ball vent valve that is in the tank end of the tube.
View attachment 1084421
I tried to reason my way to figure out which way air is supposed to be allowed to travel, and correct me if I'm wrong, air is supposed to be allowed to enter the tank through this vent tube, but not leave, yes?

OK, so as I've said before the Swedes have overthought the venting systems on these saws in the past. The sintered filter at the end of the line was for the idea that as the gas tank cooled, air from the vent end would want to go back toward the tank. So they didn't want the possibility of any dirt traveling backward.... hence the sintered filter. And yeah, there's usually a check valve too of some kind at the beginning of the tank vent plumbing. As I said, it's completely overthought and even redundant.

So for example, in the 801/80/90 series, if the plumbing is still as original....starts out with this little square plastic vent box screwed to the top of the gas tank that has a ball check. Then the vent line runs either over the carb or under and goes into the cavity where the clutch is....ends with a sintered bronze filter inserted into the end of the line.

Kevin

 

[numnutz6383]

Tilly carbs have to have the top and bottom 'sandwiches' put in correctly and they are not in the same order. Makes sure the fuel diaphragm on the bottom is hooked into the little fork. If you have good blue spark and you're sure the carb is 100%.....make sure it's timed correctly.

Not the best compression but it should start and run. Never worked on that saw....solid state ignition.....not sure what provision to adjust timing.

You gotta find that leak though if it didn't pass a pressure/vac test. Even if you got the saw started, with an air leak you could run too lean and potentially damage the P&C.

Kevin

Re: fuel diaphragm.
My diaphragm does have the little "nub" that would typically hook into a fork, but my lever doesn't have a fork. It was rebuilt with an OEM tillotson kit, no needle or lever in the kit. For what it's worth, the carb passed a pressure test with flying colors.

Re: leak
When I pressure tested I blocked off the muffler, and manifold to cylinder, and pressurized from the spark plug adapter. Which to me means the culprit would most likely be the cylinder gasket or seals, lastly, god forbid, the case is leaking somewhere. Am I thinking about this correctly?

I did have bubbling coming from the nordfeller plug, which required me to get the copper gasket from the old cylinder nordfeller plug and double them up, and that seemed to do the trick. But, the leak persisted.

OK, so as I've said before the Swedes have overthought the venting systems on these saws in the past. The sintered filter at the end of the line was for the idea that as the gas tank cooled, air from the vent end would want to go back toward the tank. So they didn't want the possibility of any dirt traveling backward.... hence the sintered filter. And yeah, there's usually a check valve too of some kind at the beginning of the tank vent plumbing. As I said, it's completely overthought and even redundant.

So for example, in the 801/80/90 series, if the plumbing is still as original....starts out with this little square plastic vent box screwed to the top of the gas tank that has a ball check. Then the vent line runs either over the carb or under and goes into the cavity where the clutch is....ends with a sintered bronze filter inserted into the end of the line.

Kevin

Yea I remember you saying the Swedes overthought these. But I wanted to give it a try rebuilding the vent hose, got some of those Chinese filters and got lucky getting the check valve from an old vent hose (stupid challenge in hindsight if you ask me, it took me way too much work to squeeze that filter into the hose). I'm fairly certain I made sure that when I installed it, the valve would allow air to flow into the tank, and block off air/fuel out.

 

[numnutz6383]

Well, I found the leak. Flywheel side seal.


View attachment VID20230523103621.mp4

 

[numnutz6383]

I took a closer look at the mating surfaces where the oil seals sit and noticed some relatively deep gouges.


Will any seal actually seal with these gouges?

 

[Cantdog]

Can you tap the seal deeper to get by the gouges?

 

[numnutz6383]

Can you tap the seal deeper to get by the gouges?

I thought of that, and started to tap them deeper, but then stopped out of fear of going too deep. Popped that seal out and was going to replace it. Now that it's out, if the new one doesn't seal I'll tap it deeper. In the meantime, do you think it's worth picking one vs the other given these two?

 

[Cantdog]

The one with the gold rim looks to have a sealer of some sort on it. The seal can go deeper just have to be careful it doesn’t interfere/ touch the bearing behind

 

[numnutz6383]

The one with the gold rim looks to have a sealer of some sort on it. The seal can go deeper just have to be careful it doesn’t interfere/ touch the bearing behind

The black one is a Dichtomatik (the edge on it is some sort of rubber like compound) I got based on, I think your recommendation, and the gold one is from McMaster, if that matters.

The bearing looks a good distance behind the actual seal mating surface. I measured 12.8mm from the case edge to the bearing, and 8 mm of total mating surface for the seal.

 

[Cantdog]

The black one is a Dichtomatik (the edge on it is some sort of rubber like compound) I got based on, I think your recommendation, and the gold one is from McMaster, if that matters.

The bearing looks a good distance behind the actual seal mating surface. I measured 12.8mm from the case edge to the bearing, and 8 mm of total mating surface for the seal.
View attachment 1084779

Looks like you have plenty of room to move it further in......just don't further than needed.

 

[Real1shepherd]

Re: fuel diaphragm.
My diaphragm does have the little "nub" that would typically hook into a fork, but my lever doesn't have a fork. It was rebuilt with an OEM tillotson kit, no needle or lever in the kit. For what it's worth, the carb passed a pressure test with flying colors.
View attachment 1084652
Re: leak
When I pressure tested I blocked off the muffler, and manifold to cylinder, and pressurized from the spark plug adapter. Which to me means the culprit would most likely be the cylinder gasket or seals, lastly, god forbid, the case is leaking somewhere. Am I thinking about this correctly?

I did have bubbling coming from the nordfeller plug, which required me to get the copper gasket from the old cylinder nordfeller plug and double them up, and that seemed to do the trick. But, the leak persisted.

Yea I remember you saying the Swedes overthought these. But I wanted to give it a try rebuilding the vent hose, got some of those Chinese filters and got lucky getting the check valve from an old vent hose (stupid challenge in hindsight if you ask me, it took me way too much work to squeeze that filter into the hose). I'm fairly certain I made sure that when I installed it, the valve would allow air to flow into the tank, and block off air/fuel out.

Hopefully, someone will chime in if that's the correct diaphragm for the bottom. Mine are all old school hook-ins.

Soap up everything. From my yrs as a plumber, I buy this blue soap tester s***t from the plumbing wholesaler. The thing about that stuff is it bubbles like crazy......very sensitive to leaks......way more so than dishwashing soap, etc.

I bought assortment kits of copper crush washers both metric and SAE. They're not that expensive and keep me from trolling the Net looking for a few crush washers. My car has tons of them...metric.

Other than timing as I mentioned before, get a really good soap leak tester and check out EVERYTHING you can think of. I do see more leak failures because of inadequate plugging of the carb/muffler...than actual leaks.

Kev in

 

[numnutz6383]

The

Hopefully, someone will chime in if that's the correct diaphragm for the bottom. Mine are all old school hook-ins.

Soap up everything. From my yrs as a plumber, I buy this blue soap tester s***t from the plumbing wholesaler. The thing about that stuff is it bubbles like crazy......very sensitive to leaks......way more so than dishwashing soap, etc.

I bought assortment kits of copper crush washers both metric and SAE. They're not that expensive and keep me from trolling the Net looking for a few crush washers. My car has tons of them...metric.

Other than timing as I mentioned before, get a really good soap leak tester and check out EVERYTHING you can think of. I do see more leak failures because of inadequate plugging of the carb/muffler...than actual leaks.

Kev in

I can't see how the diaphragm could be incorrect. For one, the same one came in several OEM tillotson carb kits, and also I was able to get an original HK-12 carburetor off a 451 that also had the same diaphragm. I'll confirm the sandwiches are right but when I rebuilt both carbs I followed the Tillotson service manual to make sure I did it right.

Not sure if you saw my exchange with @Cantdog above, but I did find a leaking seal on the flywheel side (gouged case mating surfaces). Once I replace it I hope that will take care of the leak issue, but I'll spray down the entire saw to confirm there's nothing else.

I also have to repair my Mityvac, since the pump is sticking, to do a vacuum tear, but I can use my little carb pressure tester to do the case.

 

[Real1shepherd]

The

I can't see how the diaphragm could be incorrect. For one, the same one came in several OEM tillotson carb kits, and also I was able to get an original HK-12 carburetor off a 451 that also had the same diaphragm. I'll confirm the sandwiches are right but when I rebuilt both carbs I followed the Tillotson service manual to make sure I did it right.

Not sure if you saw my exchange with @Cantdog above, but I did find a leaking seal on the flywheel side (gouged case mating surfaces). Once I replace it I hope that will take care of the leak issue, but I'll spray down the entire saw to confirm there's nothing else.

I also have to repair my Mityvac, since the pump is sticking, to do a vacuum tear, but I can use my little carb pressure tester to do the case.

I missed the exchange about the leaking seal on the flywheel side. It's maybe a good thing the saw didn't start and run.

I'm not saying your diaphragm is incorrect, I'm just not familiar with that one. If you keep seeing the same setup in other similar saws, it's probably correct.

Kevin

 

[Gumneck]

Piston looks great from exhaust side and has almost no carbon on top. Doing some cleaning and notice theres a hole in the carb/airbox area that I dont know if something is missing there or not. As seen in last pic.




View attachment 1085003View attachment 1085004View attachment 1085005View attachment 1085006View attachment 1085007

I figure I may get the Jonsereds crew on a question I have posted in the above thread.

 

[numnutz6383]

I figure I may get the Jonsereds crew on a question I have posted in the above thread.

My totally inexperienced guess, vent hose used to live there.

 

[Gumneck]

I bet yr right. The hose with the sintered(sp?) piece was just laying on top of carb when I opened it up....should have realized that straight away.

 

[numnutz6383]

I bet yr right. The hose with the sintered(sp?) piece was just laying on top of carb when I opened it up....should have realized that straight away.

What model saw is that?

 

[Gumneck]

What model saw is that?

I believe it is a 621. There are no stickers but just looking around on the net its the closest I can find.