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Author Topic: Low compression husqy 346xp.  (Read 3613 times)

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Offline wild262

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Re: Low compression husqy 346xp.
« Reply #20 on: March 29, 2018, 08:56:05 AM »
            As I said in a post or 2 back, I would just work with what you have.  Find a machine shop to mill down your head.  First thing, with cyl. and head gasket in place,  measure your squish again in several places.  Say you have 45 thousands average.  To get to an ideal 20, you would need 25 thousands milled off.  This will get your compression were it needs to be.  This way you can use your OEM gasket and no 1184 would be needed if the gasket is good.  Otherwise the gasket delete and 1184 is needed,  And I doubt your compression would be much better than 120-125lbs.  Would still run, but not well, and NOT like before. It would however "get you by".  :)   Maybe someone out there has a better answer.  Keep us posted.

Offline Dantheforester

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Re: Low compression husqy 346xp.
« Reply #21 on: March 29, 2018, 10:24:01 AM »
I contacted the company from which I bought the Hyway kit. He seemed baffled that the compression was 100psi and thinks there might be something else wrong with the saw. I don't know what that might be though. I think I'll try to find a shop that will mill it down a little and failing that this guy quoted me around 200 for a new OEM kit. 

Offline mike_belben

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Re: Low compression husqy 346xp.
« Reply #22 on: March 29, 2018, 10:55:50 AM »
There is nothing wrong with keeping the current jug.  

If it has a base step you need to make a mandrel and chuck that in a lathe, then push the jug onto the mandrel with a tailstock center and turn the material off with a lathe bit.  Iv made dowels from wood, then shot a screw through a port into thr dowel so it cant spin.  A light tap fit is best here and its okay to shim the dowel OD up with some tape to get there.  Just make light cuts.  


If the base is flat you can belt sand or hand scrub sand the meat off the base.  Measuring the 4 corners as you go until you whittle down to the desired thickness evenly.  Be sure youve got a glass surface to check flatness with.  If you were talented enough you could rough it down with a hand file then flat sand.  

I use a ceramic tile or sheet of glass with sand paper over it for a sanding surface.  If you put water in a paint pan or tub then soak the sheet, it will self adhere to the glass and stay put.  As it loads up with aluminum, rinse again.  

If you end up taking off a ton, it may lose rpm up top.  Raise the echaust ports and transfers a little to recover this.  The upper transfers also benefit from being "pointed" toward the intake side to evacuate the spent gasses and not lose the fresh charge out the exhaust port. 
Revelation 3:20

Offline mike_belben

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Re: Low compression husqy 346xp.
« Reply #23 on: March 29, 2018, 11:12:09 AM »
Additionally, you dont want ultra smooth finish, thats for metal gaskets.  Paper and sealant benefit from some tooth. Its quantified in roughness area or RA, and is what a profilemeter measures.

 These peaks and valleys create higher pounds per square inch of pressure between the surfaces.  When i lathe turn them i leave some cutter mark.  When i hand surface i leave some swirly score.  If i was taking down 20 thou id start at like 60 grit and finish maybe 200.
Revelation 3:20

Offline Dantheforester

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Re: Low compression husqy 346xp.
« Reply #24 on: March 29, 2018, 12:53:46 PM »
Thanks a lot for those suggestions Mike Belben. I wish I could say that I was even at that stage both generally in terms of my own capabilities and specifically in relation to this project which has taken a new turn into the unknown as far as I'm concerned.

I tried starting it up just to see how she'd run and the results were not very comforting. It took a lot of pulling to get her fired up (normally she'd start after three pulls with the choke open followed by one with it closed off). Once she started I opened up the throttle fully and she'd run high for a few seconds before dying immediately when I release the throttle. Little bit of smoke coming from the muffler end to that didn't strike me as your normal exhaust fumes. 

I'm stumped, but then again, the reason I embarked on this project is to learn about how the saw worked and how to fix it. So I can only look at this as an opportunity to learn more. :)

Offline mike_belben

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Re: Low compression husqy 346xp.
« Reply #25 on: March 29, 2018, 01:11:38 PM »
It needs a tune before you can knock it.  


Crank up the LA screw and get it running fast.  Adjust the L screw until you find the highest idle speed then turn LA back down until chain stops walking/shuddering.  

Now adjust the H screw so that at WOT no load there is a bit of a raspy burble called 4 stroking, this is a rich condition.  You have nailed the H setting when dogging into the wood makes that burble suddenly shift to a crisp clean dirtbike sound, called 2 stroking.  Lift off, raspy.  Dog in, sharp.  

You got this Dan, piece of cake.


Ps- i start with both screws about 1.5 turns out.  Very gently crank the H/L all the way in until the seat.  I mean very gentle or you can snap the tips inside on some.  
Revelation 3:20

Offline Dantheforester

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Re: Low compression husqy 346xp.
« Reply #26 on: March 30, 2018, 07:20:29 AM »
The chain is running fast at idle no matter what adjustments I make. The air filter and carb are both clean (new carb kit installed). ???

Offline Dantheforester

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Re: Low compression husqy 346xp.
« Reply #27 on: March 30, 2018, 08:13:00 AM »
Ok panic averted. I adjusted the carb and I have her running ok. The chain isn't creeping on idle and she's no longer cutting out. She does sound a bit rough, even raspy, at full throttle. I'm not convinced she's tuned 100% so I reckon it might be wise to take her to someone with a bit more knowledge than me. Or would it be advisable to invest in a tachometer?

Offline mike_belben

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Re: Low compression husqy 346xp.
« Reply #28 on: March 30, 2018, 08:58:55 AM »
If WOT sounds like its fouled up and held back from really ripping, its very rich.  To be sure youre describing a rich and not lean.. Turn H way out until the rpm declines and note is very lazy and cackled.  Tune your ear to it. Then turn the H screw in (cw) until it cleans up almost entirely. 

Like i said earlier you want that light raspy cackle at WOT in the air, but when you wrench down into the wood with a full bar, for the tone to change to sharp as if you flipped a pressure switch that changed modes.


Sometimes you have to tweak the L screw a bit after a major H change.  A good indication is if top end is good but its hard to get the saw to come off idle.  It should snap right up from idle to WOT when all is right.  This is a skill thatll take you a while so dont stress about it.  Do the best you can.
Revelation 3:20

Offline Dantheforester

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Re: Low compression husqy 346xp.
« Reply #29 on: April 11, 2018, 10:32:38 AM »
Hi all, I just received an oem kit and a tachometer. So I took the saw apart again and a few things popped up which I hope someone on here can help with. for a start I want to make 100% sure that I'm attaching the hose/lines to the right places. What I had done was attach the fuel line to the carburettor (I worked out that much myself :-). I attached the tank vent line to a little plastic nipple on the air intake (a pure guess). Then I attached the line running from the primer bulb to a little plastic nipple next to the fuel vent which seems to open into the fuel tank. I looked everywhere online to find a diagram of this but the majority of the 346xps out there don't seem to have primer bulbs so I had to resort to guesswork/ trial and error. One error which occurred was a kink in this primer line so the fuel couldn't return to the tank from the bulb.


I noticed that there was a vinyl ring/ spacer between the clutch drum and the sprocket. It looks a little worse for where and I can't find any reference to it on any parts diagram or youtube videos which deal with this saw. Should I just leave it?


Finally, I noticed worryingly that the head of the brand new piston I put in is badly pock marked around the edge, as is the top of the cylinder itself. What on earth could have caused that. No scoring or damage to the piston or cylinder otherwise.


Offline mike_belben

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Re: Low compression husqy 346xp.
« Reply #30 on: April 11, 2018, 09:59:30 PM »
The dents ontop the piston are from debris smacking the head.  Look inside the jug to verify.  

The little nipple off the intake is the impulse line, crankcase pressure is applied to the silk diaphragm in the carb and it flutters, acting as a fuel pump and operating the float needle.  Im not certain how it would be routed with a primer but impulses go to the carb.  

The vent hose may just go to a clip holster of some sort, look around
Revelation 3:20

Offline Dantheforester

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Re: Low compression husqy 346xp.
« Reply #31 on: April 12, 2018, 12:47:40 PM »
I made a mistake. I forgot to put the needle bearing in when mounting the piston. That's probably the culprit?!


:embarassed: I'm getting there....slowly. Lucky for me the rod looks fine and I have a brand new oem cylinder ready to go.

Offline wild262

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Re: Low compression husqy 346xp.
« Reply #32 on: April 12, 2018, 09:16:59 PM »
      You got lucky.  ;)   With all OEM, I would use the gasket if I were you.  You still should achieve 150lbs compression.  Don't use any sealer if you use the gasket.  Really no need to.

Offline mike_belben

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Re: Low compression husqy 346xp.
« Reply #33 on: April 12, 2018, 11:31:31 PM »
The needle bearing is also why you had low compression. 

Revelation 3:20

Offline Dantheforester

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Re: Low compression husqy 346xp.
« Reply #34 on: April 13, 2018, 04:35:11 AM »
The needle bearing is also why you had low compression.
Bloody hell.  Do you reckon the piston and cylinder are shot now?

Offline mike_belben

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Re: Low compression husqy 346xp.
« Reply #35 on: April 13, 2018, 06:53:33 AM »
Piston crown is fine but you havent shown the skirts or cylinder.  Id be more concerned about the little end rod bores finish and roundness. 
Revelation 3:20

Offline Dantheforester

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Re: Low compression husqy 346xp.
« Reply #36 on: April 13, 2018, 08:01:49 AM »
Just a few pics of the rod and cylinder. The rod looks OK to me anyway, although I think it has been fairly well established that I'm no expert!
   

Offline Dantheforester

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Re: Low compression husqy 346xp.
« Reply #37 on: April 13, 2018, 03:43:33 PM »
I went ahead and reassembled the saw. Passed a pressure test once I plugged the decomp.

Question: should I leave it plugged or reinsert the valve?

I got 150psi of compression then which I'm happy enough with. It's running pretty smooth now also.

I removed the vinyl spacer from the clutch but then the sprocket wheel was loose so I put it back. I still not sure about it, but I'm even less sure about a loose sprocket wheel. It might be a feature of this particular model. I bought it in 2008 or 9.

I'd like to thank everyone on here who contributed with instructive advice and encouragement. 


smiley_beertoast

Offline wild262

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Re: Low compression husqy 346xp.
« Reply #38 on: April 13, 2018, 04:13:25 PM »
I went ahead and reassembled the saw. Passed a pressure test once I plugged the decomp.

Question: should I leave it plugged or reinsert the valve?

I got 150psi of compression then which I'm happy enough with. It's running pretty smooth now also.

I removed the vinyl spacer from the clutch but then the sprocket wheel was loose so I put it back. I still not sure about it, but I'm even less sure about a loose sprocket wheel. It might be a feature of this particular model. I bought it in 2008 or 9.

I'd like to thank everyone on here who contributed with instructive advice and encouragement.


smiley_beertoast


Good work guy.  Sounds like its all good as far as cyl goes.  I don't ever remember a vinyl spacer on the cutch sprocket on these.  I will pull up a IPL and get back with you on that.  Did you replace the tore cyl gasket or patch that area with sealant?  And does this saw have the metal intake clamp?  Can't see very good in the photo.   I don't use the decomp's on my 346 builds unless the customer wants them.  There not that hard to start unless you have shoulder problems and such. Tune it alittle rich till its broke in.

Offline wild262

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Re: Low compression husqy 346xp.
« Reply #39 on: April 13, 2018, 04:42:20 PM »
I noticed that there was a vinyl ring/ spacer between the clutch drum and the sprocket. It looks a little worse for where and I can't find any reference to it on any parts diagram or youtube videos which deal with this saw. Should I just leave it?




I cannot find any reference to the above vinyl spacer.  I don't know what purpose this would serve.  Maybe someone else here knows or can find info on it.  It might be an update that was on the later saws.  I have never seen one before, and I have built several NE's. 


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