Low compression, husky 346xp

[ForesterDan]

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?

 

[smokey7]

Did you clean the transfer off the jug and install a new piston with rings of a quality brand?

 

[tpence2177]

Is the pressure tester known to have good readings on other saws?


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[brock1994]

Was the gasket the correct size? Could see that putting to thick of a gasket would decreasing pressure.

 

[spyder62]

Factory or aftermarket piston and cylinder? Did you check the squish?

 

[smokey7]

We dont even know if anything was cleaned up or replaced other than the split boot. Im currious what was changed if anything internal.

 

[ForesterDan]

Is the pressure tester known to have good readings on other saws?

Just bought the tester brand new (draper). Haven't tried it on any other saw yet though.

Did you clean the transfer off the jug and install a new piston with rings of a quality brand?

I sure did. Nice clean contact between the new gasket /case/ cylinder.

Was the gasket the correct size? Could see that putting to thick of a gasket would decreasing pressure.

I assume it is!? I searched for it using the correct serial number from the parts diagram.

Factory or aftermarket piston and cylinder? Did you check the squish?

All new OEM parts. I didn't check the swish though. Didn't have the right size piece of wire handy. I'll do that tomorrow.

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.

The gauge 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.

 

[spyder62]

When did you put the new piston and cylinder on it before or after lending it out. The few I did had around .037 squish with the gasket and 150 lbs compression. With new factory parts. Without the gasket they were all around .0185 and 180 lbs compression

 

[a. palmer jr.]

Those saws have a lot more power and rpms if you don't mess with putting oil in the gasoline but it's only for short term...

 

[spyder62]

My buddy at work needs to borrow a saw so I put one together for him to use. 2 cans of husky premix are going with it. Cheap insurance!

 

[smokey7]

Ok so it got a new oem top end after it was loaned out? Are you sure a ring didnt get broken on install? Also are you sure your decomp button is not depressed? A sure bet is to remove and plug the hole. Or in a pinch remove it clean and lap the seatvand reinstall. New oem parts never ran sounds like either a very thick gasket was used or decomp button pushed in or a broken ring. Let us know what you find out or show some pictures or what you changed and what you installed.

 

[spyder62]

How about the compression release? Did you reuse the old one? I plug mine off with the plug that comes with the new cylinder. Could be sticking open some. I guess you are opening up the throttle and pulling the rope till the compression stops rising?

 

[cuinrearview]

If your compression tester hose doesn't have a Schrader valve right at the spark plug end, I think around 100 is pretty common

 

[a. palmer jr.]

My 346 didn't come with a compression release so guess it wouldn't hurt to plug up the hole and don't use it.

 

[Okie]

If your compression tester hose doesn't have a Schrader valve right at the spark plug end, I think around 100 is pretty common

Heads Up: (and if it's not a special type low pressure schrader valve it still won't be accurate)
Yep, seen it several times. Compression gauges not indicating accurate when testing a chainsaw engine. I've seen guys overhaul a chainsaw and their inaccurate gauge read lower afterwards not aware that the problem is their test eq not being truthful.

 

[blsnelling]

If your compression tester hose doesn't have a Schrader valve right at the spark plug end, I think around 100 is pretty common

This. You MUST have the correct type gauge.

 

[dougand3]

Does anyone have a link to a low pressure Schrader valve? I have a $50 Actron gauge and it's better than the $15 HF one but I still think it reads kinda low. Will see 130 PSI on a real strong runner 272. Would expect 150+.

 

[cuinrearview]

One vote for the $15 HF one. It's been fine for me.

 

[RedneckChainsawRepair]

My $15 wally world one been going good for about 12 years now.

Still waiting to upgrade, but wont fix what aint broke. JMO

 

[RedneckChainsawRepair]

Oh there is a guy selling like 8 346's in my group site etc. Never seen him here. He has them all broke down selling as parts or whole.