Service & Maintenance Question
I have an early model Husqvarna 3120xp chainsaw. have done...
Service & Maintenance Question posted February 13, 2015 by rufus cox, last edited February 14, 2015
568 Views, 15 Comments
Question:
I have an early model Husqvarna 3120xp chainsaw. have done engine work, replaced seals etc. proceeded to do pressure/vacuum test and air leaked profusely out a (manufactured) hole in the side (not the end) of the crankshaft, clutch side. have heard varying reasons for this hole which do not seem to make sense. Is this hole supposed to allow air to come through, through the crank case and for what reason? or is it just a blind hole? If air is leaking through it, does this mean there is an internal crack? internal valve not working? Can I run the saw with it leaking air through the hole or does it indicate a potentially catastrophic internal crack? Someone said to plug it! please someone reply, I need help, have had many differing opinions from mechanics.thanks so much. please go to 3120xp.webs.com for picture of hole. (scroll down)
Photo:
Answer
Can you post a good clear picture of this hole area?
I looked in the service manual that covers this model and there should not be any air leakage from the crankcase.
and the above pressure drop would normally be from the decompression valve.
How are you pressure testing?
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http://3120xp.webs.com
Thanks so much for your reply. click on above link for picture of hole in crankshaft (scroll down). this is a manufactured hole. I sealed carburetor, exhaust, pump it up and air comes profusely from this hole. put rubber and hose clamp on hole and got it to hold pressure somewhat. my question is..why is this hole through to the crankcase and if air is coming through it, is there an internal crack that I can't see? what is the hole for anyway? mystified. Thanks, Rufus
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Rufus, This is a new one on me In the 5 years that I have been on chainsaws I never seen one like this; maybe Robert will have an idea on this or seen one. To me this not normal. It going to take someone with more knowledge of the 3120 to answer this one.
Sorry I can't be of more help on this one.
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Thanks Eugene so much for responding. Appreciate your time trying to help a lonely pilgrim in the woods! This has me and the whole mechanical community stumped. Would love some help from Husqvarna, but guess that's not going to happen. Thanks again, you're the only offer of help so far, highly appreciated. Rufus
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Rufus, Hope you don't mind to I called in some backup help from the Arboristsite forum group. These guys are very heavy in all kinds of chainsaws. I let you know if any of them has an answer on this.
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Rufus, I got a quick reply then the Arboristsite.
Here is what a staff member wrote and I quote it.
So you can stop worrying about the air leak and I have learn new too.
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Thanks for your efforts Eugene, appreciate everyone's help.
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hello mr. cox, sorry to be late to the party. I recently re-built a 3120 that a pawn shop did not want to put money into, and turned a $600.00 profit on that saw. I have extensive experience with your saw and I know that the crank must hold vaccum in order to perform properly. the only way to ensure the needle cage is lubricated is to do it manually.
is that saw running at optimum? is it very sluggish? is it hard to start?
if you are encountering problems, can you tell me the value of your compression reading for the top-end?
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I am fairly certain there is no crack in the castings. you would clearly see it if it was there.
when you pulled vaccum you sealed the intake and exhaust with rubber and inserted the pump thru the impulse hose then sucked out 10-13lbs of vaccum. did it hold pressure? if the seals are new the crank should hold that value for at least 10 minutes.
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I am guessing you got it figured out mr. cox
there is a mushroom shaped rubber plug that seals that hole. the crank must hold vaccum so the saw throttles accurately in all positions, sideways on either side, vertical, or upright...
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Robert, Would you have a picture of this part or part number for this part? I couldn't anything shown in the IPLs of the various years. This question probably come up somewhere again.
Eugene
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hello Eugene, I have a photo of it in the casting from when I re-built the pawnshop saw, but I don't know how to attach it or send it thru a computer. I will research a part number when I can find the time. I am overwhelmed right now and the chirpin beaks will not let me up.
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You would need to upload the images to a site Photobucket and using the center on the upper left of the reply window to link the photo.
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Rufus,
The hole in the crankshaft should be there, but definitely not letting air into or out of the engine. The hole is drilled into the crankshaft, and is perpendicular to a hole that should be in the end of the crankshaft, or may be filled with a little grease. Looking from the chain side of the crankshaft see if there is a hole drilled straight down the center of the crankshaft, you can take a piece of 14 or 16 gauge wire and poke it down that hole snd it should meet the perpendicular hole that you show in your photo. The intent of these holes, Is when your clutch, drive sprocket, and drive sprocket bearing are all installed, you can use a grease gun with a needle tip to pump grease into the crankshaft and out into the drive sprocket bearing.
I hope this helps and makes sense, Also since this hole is normally filled with grease, no air will leak through it
Karla.
PS. I am Not a Husqvarna Representative or a Repair Service, just an experimental chainsaw person.
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Rufus,
Just one more piece of Info, when you do get your chainsaw back together and the clutch, drive sprocket, and drive sprocket bearing are back in place, Do Not over grease the sprocket bearing by pumping too much grease into the end of the crankshaft, maybe one pump on a regular small grease gun, otherwise the excess grease will end up inside your clutch, which you definitely Don't want. The inside of the clutch should be clean and dry, no oil or grease inside. Also, alot of people that have chainsaws never take the drive sprocket bearing and drive sprocket apart, which is also wrong and a big mistake. That should be cleaned, inspected, and regreased periodically, this will aide in your sprocket running properly and driving the chain effectively, but with the hole in the crankshaft feature or option, alot of individuals just keep pumping grease into the end of the crankshaft, which obviously is Not a good idea either, so its kind of a catch 22.
Hope this helps again.
Karla
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