Jonsared 2040 turbo stalls after a few seconds under load.

[SawThings]

My saw was running fine until it wasn't. Took it apart and the fuel line was cracked and had leaked everywhere. I got a new fuel line and put it in, also cleaned up the filter and sprayed the carb out with cleaner while I had it off, and blew some air through the fuel hole on the carb in case there was some fuel line chunks in there.

Saw starts and idles fine now, and it'll cut normally for 2-3 seconds and then it'll bog down and die unless you take the load off immediately. Seems like it's starving for fuel, so I took off the fuel filter and it runs fine again at high speed, although idled a little high, so I put in a new fuel filter and it's bogging down again. Took it all apart again to make sure I didn't kink the fuel line or something, all looks good, gave the carb another quick clean but no luck. Still bogs down after a few seconds unless I take off the bran new fuel filter. Can anybody point me in the right direction on this? Not sure what to do next. Fuel diaphragm maybe? Was running fine before the line cracked.

 

[rupedoggy]

Spraying carb cleaner and blowing on the fuel inlet may be fine once in a while but you need to take that carb apart and put new diaphragms into it and clean all the passages and adjust the fulcrum perfectly. Check the little screen inside. Then check the pulse line for cracks and problems. You may have an air leak if this does not do it.

 

[SawThings]

Thanks rupedoggy, I guess I was trying to be lazy, since it was running fine before thought I'd leave it alone other than the fuel line that broke. I took the carb apart just now and cleaned it out, screen was pretty dirty. It's cutting well again now. Bit of a stumble sometimes the moment I give it full beans from idle, but just at the start, then it gets up to speed. Could maybe tune that out somehow but at least it's cutting again!

 

[Bob Hedgecutter]

Those are getting a few year of age on them now, then couple that with your fuel and the fact the fuel line was toast- you need to do as said above, plus I would replace all the rubber while I was in there.

 

[rupedoggy]

I don't know about this "it was running fine until it started having problems". Why do people say this?
"he was perfectly well until he got sick". How about "he was alive until he died" "I was able to buy things until I ran out of money!" "I was happy until I got sad"

 

[SawThings]

I don't know about this "it was running fine until it started having problems". Why do people say this?
"he was perfectly well until he got sick". How about "he was alive until he died" "I was able to buy things until I ran out of money!" "I was happy until I got sad"

Was a bit of deadpan humour mixed with the fact it happened suddenly.


I bought an Echo 590 cause I needed something bigger anyway and still can't get the love from my 2040. idles and runs great, revs up nice now after some tuning. It starts cutting like normal for about 2-3 seconds, then bogs down and seems like it's starving for fuel. Maybe there's still a problem with the carb and needs a full rebuild, a chunk of fuel line in there I couldn't clean out without removing the welch plugs, or maybe a bad diaphragm.

I checked the compression and cold I got 130psi, after warming it up, dropped to 105psi, which I found odd, as with a vehicle you usually get higher compression when warmed up. Seems a bit on the low side, maybe when my fuel line broke I leaned out the saw and burned it up a bit? Stuck my borescope down the spark plug hole and took a few pics.

I guess I'll rebuild that carb and put a new ring on the piston, smooth out the bore, doesn't look too bad but I can get one of those piston/cyclinder combos if it's ugly enough.

 

[rupedoggy]

Junk

 

[Bob Hedgecutter]

Yeah, na- no amount of carb cleaning or diaphragm replacing is going to fix that.
Time to get the tools out and tear the top end off that saw- throw parts away and replace them.
Get the cylinder off the saw, take lots of photos of the interior of the cylinder and the piston and people can advise how much is toast.
Minimum new piston and ring and a whole lot of fun trying to clean up the cylinder.

 

[SawThings]

Minimum new piston and ring and a whole lot of fun trying to clean up the cylinder.

My mill and/or a hone should do it, but if it's cheap enough I might just get a new one. I haven't looked into it at all, but it'd be nice to bore it out a bit if it's doable, and a bigger piston is available.

 

[Bob Hedgecutter]

My mill and/or a hone should do it, but if it's cheap enough I might just get a new one. I haven't looked into it at all, but it'd be nice to bore it out a bit if it's doable, and a bigger piston is available.

Ah, chainsaw bores are not to be put anywhere near mills or hones- you just tear off the coating and render them useless (or more useless as the case may be) and certainly cannot be bored out for a larger piston- least not modern made ones that do not have a punch out bore sleeve and cast iron cylinder!

You clean the transfer from the piston out of the pot you have- if it is not too far gone.
Or you buy a new one.

 

[SawThings]

Nevermind that plan then. I thought it'd have a liner, not just plating. Do the cheap Chinese replacements come with a new coating in the cylinder? I can get a new cylinder/piston kit for about $30 CAD, seems like it's worth a try at that price, if it's not total junk.

 

[Bob Hedgecutter]

You can toss the dice on a corvid kit if you want.
At least at that price it will not hurt as bad if it does it again- which it WILL do if you do not figure out why it burned up in the first place.
It is either a fuel mixture problem, or an air leak problem- if you don't correct either it will just keep burning out pistons and cylinders as fast as you can buy them and fit them.

 

[SawThings]

I can't say for certain why it happened, it's a a saw I bought used 10 years ago. I'd suspect the fuel line cracking apart and running lean from plugging jets or just the fact the fuel line was cracked and leaking. I have no idea now long a small leak persisted until it finally wouldn't run when the fuel line completely broke. When I took it apart though, it was just disintegrating in my fingers. Maybe best to throw a cheapo in there first and confirm it was the fuel line that caused the issue. I guess I'll know if it happens again soon.

When the saw finally did shut down, I did notice a slightly different smell, and noticed more heat on my left hand radiating from the muffler, from what I recall. I'll know to more cognizant of the early sings of something like this in the future. Was just an old saw to me before it broke, but I'm getting a bit more educated now, thanks for being a part of that!