Jonsered 2172 / Husqvarna 372 loosing power when it gets hot

Usmc98 · Apr 11, 2022

Started my Jonsered 2172 for the first time in a year was stored with empty tank/carb. Was running out of gas so i replaced a worn fuel line. Saw runs great then after about 10-15 minutes it starts to loose power and seems to be running hot. It seems like it is lean and revs up a little but has no power in the cut. I can rev it a couple of times and it gets it's power back a little and then looses it again.
Spark plug looks good maybe a little lean so i adjusted the high side out to richen it and it was about 1/8 of a turn from being adjusted out with blockers installed. It didn't want to restart maybe only fire for a second, maybe because it was hot.
I do believe i ran into the same issue last year where it didn't want to start when it was hot.

John Stryker · Apr 12, 2022

It could be a plugged fuel tank vent. The next time you have this problem, crack the fuel cap to equalize the vacuum and if it runs better you know the vent is plugged.

Usmc98 · Apr 12, 2022

John Stryker said:
It could be a plugged fuel tank vent. The next time you have this problem, crack the fuel cap to equalize the vacuum and if it runs better you know the vent is plugged.

I was thinking the same thing. As per the picture there is two nipples and i wasn't sure which one the vent tube went to so i connected it to the one towards the handle. Are both of the used and which one is for the vent?

John Stryker · Apr 12, 2022

Usmc98 said:
I was thinking the same thing. As per the picture there is two nipples and i wasn't sure which one the vent tube went to so i connected it to the one towards the handle. Are both of the used and which one is for the vent?

View attachment 980664 View attachment 980665

I'm not sure which nipple to use, but I think it needs to be an open hole to atmosphere.

TRTermite · Apr 12, 2022

I have worked on some J 2186 s' that came with the vent hose from vent to air intake box (after filter before carb I think been a while). They got eliminated when new vents (OEM From Husqvarna dealer) were used. They told me the older/original vents were problematic with fines the original vents were many years old as are the 2186s' and your 2172 . I would question the carb metering diaphragm getting stiff, does it start (When Cold ) easy?

Bob Hedgecutter · Apr 12, 2022

John Stryker said:
I'm not sure which nipple to use, but I think it needs to be an open hole to atmosphere.

Not sure- does this help any?

NOTE: This is the air box of a 2171, not a 2172.

TRTermite · May 18, 2022

The fuel line goes to the brass barb on the carb. The vent hose/line goes on a plastic barb going into the tank, you might be able to see this PTO side under the carb box floor above the tank. The fuel line goes directly into the tank without any fittings.