Jonsered 2077 Runs well for 10 minutes, Loses Power

[krag]

I finally had a Jonsered 2077 turbo saw fixed today; it runs for 15 minutes or so then loses some power, idles up and down when you give it gas. Sam thought this is probably the carburetor, with the alcohol in the gas that does damage over time. Thoughts on other causes?

 

[Nutball]

How about a video so we can hear it?

 

[krag]

I don't have a video camera and it would involve running it a long time to capture the defect.

Starts up OK and runs strong 10-15 minutes and then surges and loses power though keeps running. Give it a rest for about the same and runs well again for a while. It sat for too long; friend thinks it was the ethanol may have degraded the carb..

 

[Stump Shot]

Seals may just be starting to go out on you.

 

[huskihl]

Tank vent or coil might be bad

 

[Nutball]

Sounds heat related, so it could be a seal of some sort, or maybe the engine is overheating and either loosing compression, or loosing power to predetonation.

Maybe clean off the engine cooling fins if they are dirty, and try 93 octane gas. I wonder if the ignition could be getting weak when hot?

 

[krag]

It looks like Ebay has cheap Jonsered 2077 carbs. and ignition coils, are these worth a try?

 

[Dub11]

It looks like Ebay has a lot of cheap Jonsered 625 carbs. and ignition coils, are these worth a try?
https://www.ebay.com/itm/CARBURETTOR-CARBURETOR-Carb-For-JONSERED-625-630-Chainsaws-Rep-P-N-503-28-03-16/231882629324?epid=1546408842&hash=item35fd4820cc&enc=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&checksum=231882629324ac9ea58ab01a48dea2487b14ade395d3

https://www.ebay.com/itm/Ignition-C...775903?hash=item1a11fa735f:g:w14AAOSw6oBXEaS7

Coil is always worth a shot but that is the wrong carb in the picture.
https://www.ebay.com/i/302978967879...MIqYLEudet4gIVCr3ACh3pQA5vEAQYAyABEgKqJfD_BwE

You need one with the impulse line on top. It'll be the same as a 670.

 

[krag]

Oops, it's a Jonsered 2077 Turbo, sorry for the confusion.

 

[Dub11]

Oops, it's a Jonsered 2077 Turbo, sorry for the confusion.

Oh in that case send that dangerous P.O.S to me.

Have you tried running it then when it starts to bog go and crack the gas cap to vent the tank to see if that helps?

 

[krag]

Will try.

 

[smokey7]

Any of these black and red saws have a home here. No matter if a mistake was said in the model or not still a great saw

 

[krag]

I finally got the saw running well again this week; the oiler and recoil had been done 6 months ago, saw ran crappy. Stopped at a small shop with Sam in Deep River. Knocked on door, waited, called the guy's number, no sign of life. Finally as we were driving away wife shows up at the door, ghost like. We circle around back, she says husband is in the bathroom. He comes out, opens up shop and checks out the saw. Bad plug, someone had put the wrong one in. Finally running great again. I let him do the chain, though he took off too much. It was new, with minor abrasions, but it is only good for one sharpening now.

 

[krag]

I had the carburator rebuilt; still the same problem. Sam was thinking adjusting the high and low needles may help now but the crankcase may have a leak which might explain the problem. The power is "pulsing" in his opinion, so he is thinking the seals are compromised. Compression is high.

The parts supplier said this:

If a carb kit has been installed and it did not change anything, I would remove the muffler and spark plug and take a look at the cylinder, and look for any scratches. I usually run a pick on the cylinder wall, and is I feel anything at all the cylinder is ruined. Also most mufflers have a little screen in them, take that out and clean it. Next you need to do a compression check to see if it is within specs. pressure checks need done on the fuel lines to check for leaks, need to do a crank seal pressure test to see if they leak. This pretty much covers everything that can go wrong with a 2 cycle engine. I hope this helps. Unfortunately you start getting into cylinder and crank seal replacements, it is not worth it unless it is a high end piece of equipment.

 

[krag]

Fixed, turned out to be a simple gas filter replacement. A repair shop did the tune up for around sixty bucks, runs fine again.