3120xp dies when I throttle

[J D]

I have a piston stop in the cylinder and have used my socket wrench and impact driver (set for right hand tightening, for left hand loosening) to no avail. Any advice?

Piston stops are good at wrecking pistons... a length of chord is usually a safer bet, just make sure you don't lower the piston far enough to get it into a port when you feed it into the cylinder

 

[Kevin in Ohio]

For what it's worth, I had an older Stihl that would idle fine but would not rev at all. Ended up being either the coil or condenser and when I replaced both(at the same time) it ran great again. Is yours electronic? All I'm suggestioning is don't rule ignition out.

 

[internet.user.human]

Ok, I got the flywheel off and plugged all the spots I know to plug for a pressure test. I have a piece of rubber gasket between the muffler and the cylinder and a plate covering the intake where my mityvac is hooked up.

In the attached video, I can hear air escaping on the clutch side of the saw, but see no bubbles from my soapy water spray.

Is it time to pop open the cylinder?

View attachment IMG_5420.mov

 

[Bob Hedgecutter]

Spray some water over the grease hole center of the crank shaft stub.

 

[internet.user.human]

Spray some water over the grease hole center of the crank shaft stub.

I get nothin’.
View attachment IMG_5424.mov

 

[Bob Hedgecutter]

Okay, maybe your directional hearing is off- start squirting soapy water elsewhere- for what its worth I tend to use more water spray per optional exit point.

Oh and to test that grease delivery point- it has to be A: clear of grease and B: the side delivery (grease to needle bearing) hole must be blocked with digit pressure.

 

[internet.user.human]

Okay, maybe your directional hearing is off- start squirting soapy water elsewhere- for what its worth I tend to use more water spray per optional exit point.

Oh and to test that grease delivery point- it has to be A: clear of grease and B: the side delivery (grease to needle bearing) hole must be blocked with digit pressure.

I sprayed it on the flywheel side of the case and got no bubbles there either. I’m pretty certain the air is coming from the clutch side of the case, I can’t hear the air escaping as well when listening from the flywheel side. I also don’t hear much at the muffler or carb end.

I am a little confused about the grease delivery point, is that on the clutch side? Was I spraying water anywhere near it?

Thanks!

 

[J D]

Grease delivery point is that hole in the centre of the shaft.
I'd be removing the oil pump. Some of the bolts there can go through the case & 1 may be loose. I had a 390XP like that, it was definitely factory but all the others I have had apart didn't have the same holes. I would expect there will be a seal behind there that you can't get the soap spray on without removing the pump too

 

[Bob Hedgecutter]

Grease delivery point is that hole in the centre of the shaft.
I'd be removing the oil pump. Some of the bolts there can go through the case & 1 may be loose. I had a 390XP like that, it was definitely factory but all the others I have had apart didn't have the same holes. I would expect there will be a seal behind there that you can't get the soap spray on without removing the pump too

yep thats the next port of call- after confirming no centre shaft leak.
And there is one of them Husqvarna specific O rings on the inside lip of the pump.

 

[internet.user.human]

yep thats the next port of call- after confirming no centre shaft leak.
And there is one of them Husqvarna specific O rings on the inside lip of the pump.

Ok thanks guys. I’ll remove the oil pump next and see if I can find the leak there.

And uh oh, Husqvarna specific o ring sounds like I need to be extra careful?

 

[Bob Hedgecutter]

I am a little confused about the grease delivery point, is that on the clutch side? Was I spraying water anywhere near it?

Some Husqvarna cranks have a hole drilled in the crankshaft through that dimple and an intersecting hole drilled through the side of the shaft to connect to the central one that allows the clutch needle bearing to be greased from the exterior.
You have to ascertain if the hole is A: there (is not in all saws), B: there is a side hole at the bearing position and C: if indeed that hole continues into the crankcase (as some 3120's do)

There is a service bulletin around somewhere from Husqvarna that explains how this must be plugged (if right through to interior of case) to perform a pressure/vacuum test.

 

[internet.user.human]

Some Husqvarna cranks have a hole drilled in the crankshaft through that dimple and an intersecting hole drilled through the side of the shaft to connect to the central one that allows the clutch needle bearing to be greased from the exterior.
You have to ascertain if the hole is A: there (is not in all saws), B: there is a side hole at the bearing position and C: if indeed that hole continues into the crankcase (as some 3120's do)

There is a service bulletin around somewhere from Husqvarna that explains how this must be plugged (if right through to interior of case) to perform a pressure/vacuum test.

Could you point me to said service bulletin? I searched those keywords with 3120xp and couldn’t turn anything up. I looked in the chainsaw manual thread but couldn’t find what I was looking for there either.

Thanks!

 

[Bob Hedgecutter]

Nope- I'm heading in for surgery shortly, so you will have to do your own search for "pressure and vacuum testing 3120XP" there is lots of reading on the subject within this forum alone.
Basically if there is a small pin hole in the side of your crank about where the clutch needle bearing sits- seal it with a couple of wraps of tape.

 

[Maintenance supervisor]

Nope- I'm heading in for surgery shortly, so you will have to do your own search for "pressure and vacuum testing 3120XP" there is lots of reading on the subject within this forum alone.
Basically if there is a small pin hole in the side of your crank about where the clutch needle bearing sits- seal it with a couple of wraps of tape.

Good luck with your surgery!

 

[Bob Hedgecutter]

Good luck with your surgery!

Cheers- just a simple day surgery but takes all day with the travel to and from. Bonus being I now have a card to get through airport security I never used to need!