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Low compression husqy 346xp.

Started by Dantheforester, March 22, 2018, 05:31:01 PM

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mike_belben

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.  
Praise The Lord

Dantheforester

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). ???

Dantheforester

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?

mike_belben

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.
Praise The Lord

Dantheforester

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.


mike_belben

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
Praise The Lord

Dantheforester

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.

wild262

      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.

mike_belben

The needle bearing is also why you had low compression. 

Praise The Lord

Dantheforester

Quote from: mike_belben on April 12, 2018, 11:31:31 PM
The needle bearing is also why you had low compression.
Bloody hell.  Do you reckon the piston and cylinder are shot now?

mike_belben

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. 
Praise The Lord

Dantheforester

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!
 

Dantheforester

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

wild262

Quote from: Dantheforester 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


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.

wild262

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. 

steele109

Parts tree doesn't show a plastic washer on any models 1999-01. Except that funky trio brake model.

Dantheforester

Quote from: wild262 on April 13, 2018, 04:13:25 PMDid you replace the tore cyl gasket or patch that area with sealant?  And does this saw have the metal intake clamp?  
I did replace the gasket. It does indeed have that clamp (little devil).  

I'll be taking off that "vinyl spacer". I reckon that it may have been a strand of bailing string that wrapped around the shaft and fused with the heat to create a pretty convincing washer.

Thanks again.


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