Low compression husqy 346xp.

Dantheforester · March 22, 2018, 05:31:01 PM

Hi all,

I'm looking for help with a Husqvarna 346xp rebuild. I replaced the rubber boot in the manifold (which was broken), the gasket and the cylinder and piston (both scored). After all that I did a pressure test with no leaks so I went ahead and put her back together. Then came the compression test and she only scored a meager 100psi.

Would anyone have a suggestion as to where to go from here?

starmac · March 22, 2018, 06:09:32 PM

As well as I like my 2 346's I have read that they can be upgraded to be even better with a rebuild, I forget which jug and piston to use though.
I would nearly bet if you still have 100 pounds compression, that your jug can be cleaned up though, so new piston and rings, may very well be all you need.

sawguy21 · March 22, 2018, 06:56:57 PM

Are the p&c new? Are they OEM or aftermarket? Is the cylinder gasket correct thickness for your saw? Are you certain the compression gauge is accurate?

Dantheforester · March 22, 2018, 07:04:11 PM

The new piston, ring and cylinder are all OEM and the gasket is the correct one. The pressure gauge is brand new (Draper). It read 60 psi before I replaced the impulse line nipple, then it only improved to 100psi. There were no air leaks when I pressure tested with a vac pump.

For a bit of back story: I loaned the saw to my bro-in-law who I suspect ran it on straight petrol (or near enough to it). The electrode on the spark plug was snow white when I got it back.

I've owned and used chainsaws both privately and professionally for fifteen years but this is the first time that I took one apart to this extent myself. So my knowledge of all the little things that can go wrong is little enough.

starmac · March 22, 2018, 07:12:30 PM

I mis read your post and didn't realize you had put a new jug and piston already. Does it crank and run, it could be your gauge is off. Another question is is the cylinder dry, or are you getting gas in it.
You may need to do a squish test, it is possible you need to delete the base gasket, others more familiar with that will surely be along.

realzed · March 22, 2018, 08:10:24 PM

Is your compression test before or after the saw has been broken it? I'm sure the PSI rating will go up considerably after the rings have seated with some usage and a bit of carbon fills in the ring gaps and the top of the piston to some extent..

barbender · March 22, 2018, 08:51:02 PM

All I know for sure is, I've never seen a happy ending to a loaned chainsaw story on here👎

wild262 · March 22, 2018, 09:28:53 PM

If 100psi is correct, than you got problems somewhere that's for sure. I've put on a lot of these OEM kits, and usually get compression of 150 lbs with gasket. At this point, I would do a pressure & vac test. Maybe plug the decompression valve as well. Keep us all informed.

wild262 · March 22, 2018, 09:47:42 PM

I forgot you did a press. test. I would also check with another compression tester as well. Your squish ideally is no less than 18-20 thousands. But it will be more than that I'm sure with OEM gasket, maybe 30-40. Check that with thin wire solder. There are 2 different OEM 346 cylinders and piston bores as well. You may not know this. The OE (old edition) 42mm, and the NE (new edition) 44.3mm. Make sure they are not mix-matched. I say that because, I have gotton a OEM NE P/C kit that had a OE piston included. That doesn't make for very good compression. If you can't find the problem, tear it down again and measure everything.

starmac · March 22, 2018, 11:11:30 PM

Quote from: barbender on March 22, 2018, 08:51:02 PM
All I know for sure is, I've never seen a happy ending to a loaned chainsaw story on here👎

I should get one of my 346's back this week, I loaned it to my kids and it has cut every stick they have heated their house with the last two winters, so am wondering how it will be. I know it still at least runs, cuz they ain't froze yet.

wild262 · March 23, 2018, 10:42:59 AM

Quote from: starmac on March 22, 2018, 11:11:30 PM
Quote from: barbender on March 22, 2018, 08:51:02 PM
All I know for sure is, I've never seen a happy ending to a loaned chainsaw story on here👎
I should get one of my 346's back this week, I loaned it to my kids and it has cut every stick they have heated their house with the last two winters, so am wondering how it will be. I know it still at least runs, cuz they ain't froze yet.

There ya go! Lol We need to take care of our kids don't we! I think I'd have to give'em 1 of my rough old 350's - just in case! Neither burns wood yet, but 1 is thinking about it more.

starmac · March 23, 2018, 03:46:08 PM

Funny you should say that, when they picked it up, I was going to give them my 455 which I had had riding in the back of the pickup for a couple of months. I had been using it for a mill saw, and it starts easy and run perfect, but it had been raining for nearly two weeks, so I had not started it. It would start right up, but then die as son as you touched the throttle, I tinkered with it a few minutes then just gave them the 346 with a stearn warning.

Dantheforester · March 24, 2018, 03:55:54 PM

Hi, I haven't gotten back to the saw since. Spent a couple of hours yesterday tidying my workshop while looking for my calipers which I didn't yet find. Thanks for the suggestions so far. Hopefully the problem will turn out to be one of them.

Dantheforester · March 27, 2018, 09:38:49 AM

Hi all. I Couldn't find a digital calipers (either my own or in two local hardware shops) but decided to go ahead and do the squish test anyway just for the craic. I checked the decompression valve with a little soapy water and it's air-tight when closed. Anyway, there is literally NO squish on the solder. I actually think I could have used my pinkie finger for the test! What the heck? I used an OEM piston and cylinder kit with the (apparently correct) gasket. Maybe I need to machine down the deck?

Here's a link to the kit I bought https://www.eurosmallengineparts.ie/husqvarna-346xp-350-351-353-cylinder--piston-45mm-nikasil

And the gasket: https://www.eurosmallengineparts.ie/husqvarna-346-350-351-353-xp-base-gasket?search=5038944-01

EDIT: As anyone who followed those links may have worked out, the cylinder and piston kit are not OEM but are Hyway....which well, may be part of the problem?

wild262 · March 27, 2018, 10:20:54 AM

I just saw your edit. Yes, that is not true OEM. That's the Hyway 45mm big bore kit. Tell you what I would do. Simply delete the base gasket and use 1184-94 gasket sealer, or as some call 3-bond. This will raise your compression some, but may not be enough. Got nothing to lose at this point. Or you could go buy a "true" OEM kit for around 120-130 $. That should put your troubles behind you. To help you out alittle more, I would do some trading with you for an OEM kit I have. I have 5-6, so no big deal. Your call.

Dantheforester · March 27, 2018, 10:48:14 AM

Quote from: wild262 on March 27, 2018, 10:20:54 AM
I just saw your edit. Yes, that is not true OEM. That's the Hyway 45mm big bore kit. Tell you what I would do. Simply delete the base gasket and use 1184-94 gasket sealer, or as some call 3-bond. This will raise your compression some, but may not be enough. Got nothing to lose at this point. Or you could go buy a "true" OEM kit for around 120-130 $. That should put your troubles behind you. To help you out alittle more, I would do some trading with you for an OEM kit I have. I have 5-6, so no big deal. Your call.

Thanks for the suggestion and offer. I'm guessing that you're in The States? I'm on the other side of the puddle in Ireland so I reckon shipping could be pretty expensive in terms of doing a trade.
I'll try without the gasket for the moment and see how that does. I have some Indian head gasket shellac. Would that do the trick?

mike_belben · March 27, 2018, 11:19:03 AM

Its worth a try. Big things are to be certin the jug base and the block face are clean with no step at the parting line... And DO NOT get antsy to crank it over just for a test feel. Let the stuff really cure overnight.

wild262 · March 27, 2018, 01:27:56 PM

No I hadn't really looked at your location until after you told me. Just assumed you were here in the US. You really ought to get that 1184 or another would be Dirko. Dirko is what Stihl uses. I just don't like to use it on Huskys because of the color being red for coverage reasons. As far as the Indian head, I can't say but I doubt it will work. The 2 products above are proven to work for sure. That's the only 2 I would use. If you got anyone with a milling machine you could take off enough material from the bottom and still use your gasket for the squish of your choosing. 20 thou. would be perfect. That's the way I would go hands down if it were mine. With the 1184/dirko you might get 120-130 lbs, if your lucky.

Robertmac · March 27, 2018, 03:56:29 PM

Quote from: barbender on March 22, 2018, 08:51:02 PM
All I know for sure is, I've never seen a happy ending to a loaned chainsaw story on here👎

Never a lender or a borrower be. all my life I have lost out to friends on loaned items as I cherish everything I buy, simply because I went out to earn it to buy it because I needed or wanted it at the time, so it offends me when a friend would dare ask if they can borrow my tools or electrical items.
I will do jobs for them for nothing before I will lend out anything now to anyone.
I have borrowed in my younger days and paid the price of marking it or damaging it and having to fork out for a brand new item.
Seems I'm the fool for replacing the broken or marked item as no-one I have ever met will do this for me and certainly not in present day society.
Which is why I cannot afford to lend things nowadays.

Dantheforester · March 29, 2018, 06:45:01 AM

Thanks a lot for the suggestions. Unfortunately an OEM cylinder and piston kit seems to be difficult to acquire over here. The best deal I could find online is for £270 from a UK website. I went down to my local Husqy dealership and the guy there gave me a talk about how he had to wait for weeks to receive a single shock absorber spring and shared with me his suspicion that they weren't paying their bills. Well I don't know anything about that.

Anyway, the customs charges for having an OEM kit imported from the USA are usually prohibitive, but may still work out cheaper. But could anybody help me understand why a replacement part, spurious though it may be, won't fit the purpose that it was supposedly designed for. Are there other brands apart from Hyway which would have the same dimensions as an OEM cylinder?

My other option is to have someone machine down the deck a bit. It this a difficult process? Should I let a person with no specific experience with chainsaws carry this out?

wild262 · 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.

Dantheforester · 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.

mike_belben · 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.

mike_belben · 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.

Dantheforester · 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.