Husqvarna 257 acting funny

[Keithandstef]

Ran the 257 pretty hard today and all of a sudden it wouldn't start up well. Kept dying. I noticed one I the bolts that holds the muffler in place is missing. No where to be found. I'll buy another one but could that be causing the sputtering?

 

[calebng15]

I'd pull the muffler off and take a look at the piston. Does it feel like good compression?

 

[Keithandstef]

It was running well. Got very hot though. I'll check the piston.

 

[KennyPete]

Should have bought mine

But in all seriousness, pull the exhaust off and check the piston.

If that looks good, pull the plug and check for spark.

If that checks out, turn it upside down and pull it a few times to see if fuel runs out (check for flooding).

A missing exhaust bolt could cause sputtering, but I'm more inclined to believe its related to something else.

 

[Keithandstef]

Should have bought mine

But in all seriousness, pull the exhaust off and check the piston.

If that looks good, pull the plug and check for spark.

If that checks out, turn it upside down and pull it a few times to see if fuel runs out (check for flooding).

A missing exhaust bolt could cause sputtering, but I'm more inclined to believe its related to something else.

LOL. I was thinking the same thing. The piston looks perfect on the exhaust side at least (can't say for sure on the other side). I can't put the muffler back on fully without that bolt (which I'll order in a minute). Can I check compression without the muffler on? The pull cord feels like it has a little less resistance than before. Maybe it's in my mind.

 

[KennyPete]

Yes, you can check compression without the muffler on.

Also, try taking out the compression release and cleaning it. In a rare instance, I had a piece of carbon slightly holding one open.

 

[Keithandstef]

I looked at the piston up and down and it looks like the day is was born. Compression is a pitiful 115 though. To be honest, I've never tested the saw with my tester, and I don't trust the tester very much. The fact that the piston looks so good makes me think the reader is wrong. I'm going to get my muffler bolt, re-assemble her later this week and see how it goes. I noticed it wasn't oiling well either as the work progressed. Weird.

 

[albert]

Check your fuel hose. If it is more than a few years old, it's probaly due.

 

[Keithandstef]

Check your fuel hose. If it is more than a few years old, it's probaly due.

Good call. I found the fuel filter part #503443202 on ereplacementparts.com but the hose and some little gizmo in the middle of the hose (503735801 and 501768302 are listed on the diagram but not for sale). Two questions. Are all these important to replace?

1) where is a good parts place for these pieces?
2) how tough is it to change a furl line. YouTube is showing me a bunch of saws but not this model. I'm nervous.

Thanks.

 

[bacon K5]

If you hold the recoil and let go of the saw, can it support its own weight with compression, or does the rope pull out? If it can't support its weight or close to it, the gauge might be correct. The piston doesnt have to look bad for there to be a compression issue either. Rings could be stuck, something else could have broken inside. Pull the top end off - it's not hard to do.

 

[Keithandstef]

OK, most of the Youtube videos I see show some generic fuel line be used for a replacement. The part for the 257 seems more custom.

If you hold the recoil and let go of the saw, can it support its own weight with compression, or does the rope pull out? If it can't support its weight or close to it, the gauge might be correct. The piston doesnt have to look bad for there to be a compression issue either. Rings could be stuck, something else could have broken inside. Pull the top end off - it's not hard to do.

OK, I swung by the house and lifted up on the pull cord, and it comes out pretty much as the saw gets lifted off the ground. If I pull in the starter a few times, it will support the weight of the saw (as compression build I suppose). I just can't get over how good the piston looks. I looked down the hole from the spark plug and the top looks good too. When you say rings could be stuck, what do you mean?

 

[bacon K5]

Rings should fit freely in the groove(s) in the piston. They can become stuck in the grooves from mechanical damage or thermal damage which will prevent them from properly contacting the cylinder wall to generate compression.

You said it ran hot - how do you know it was hot and how hot do you mean? Hot enough to melt/warp metal?

Pull the cylinder off and have a look. If the piston and cylinder look good, you might be able to get away with a new set of rings

 

[Keithandstef]

It ran hot as the chain got tight. Maybe just the bar got hot. We were into some 17" across wood which is pretty big for this saw. It did fine, but it started acting funny on re-starts. ONce it got up to speed, it cut well. I cant get a good shot of the insides. The piston and cylinder look great.

I can't run it again until I get that muffler bolt. The uncertainty about what's going on is driving me nuts.My hope is that the lost muffler bolt is the culprit of the sputtering, and the compression issue is just my tester being crap.

OK, so dumb question. Do I just pull off that big finned thing to get a look at the rings and such? And you said the ring should move freely in the groove?

 

[bacon K5]

That's a 257? That thing is remarkably clean for it's age.

Not trying to be mean, but referring to the head as the "big finned thing" makes me think you shouldn't attempt this on your own. You'll need a ring compressor for reassembly and youll have to take off other various pieces to do this.

Missing one muffler bolt should not impact your saw the way you describe. The small air leak caused by a missing screw might actually help it run better since it breaths easier. A muffler port is essentially the same thing - creating a bigger space for exhaust to get out. You can start and troubleshoot your saw with 1 screw.

 

[apemoreton]

Have you checked your decomp valve? It might be getting stuck. But all fairness as others said if your not mechanicaly minded I'd leave it to someone that is

 

[Keithandstef]

Have you checked your decomp valve? It might be getting stuck. But all fairness as others said if your not mechanicaly minded I'd leave it to someone that is

Agreed. If I decide to get into this thing, it'll be someone else doing the work for pay. I think the saw is probably suffering from a bad ring or seal somewhere.

 

[calebng15]

Does your compression reader have a schrader valve in it? What is the possibility that you sucked something up in your gas tank, causing to not get enough fuel? Also, could you have sheared your key on the flywheel, causing the timing to be off?

 

[calebng15]

Agreed. If I decide to get into this thing, it'll be someone else doing the work for pay. I think the saw is probably suffering from a bad ring or seal somewhere.

Too bad you weren't closer! We'd fix her right up!

 

[Keithandstef]

Does your compression reader have a schrader valve in it? What is the possibility that you sucked something up in your gas tank, causing to not get enough fuel? Also, could you have sheared your key on the flywheel, causing the timing to be off?

The fuel filter looks darn near new. I've ordered another one and will replace it and the hose just for grins. The compression tester has a little pin in the middle of the plug that threads into the spark plug housing. Not sure about the flywheel. The saw sure was running rough when it got late into the sawing session. Joust couldn't get it to fire up. I'm itching to test it but want to wait and get the muffler properly affixed with both bolts.

 

[Keithandstef]

I'm putting it back together with the muffler and such later this week (waiting on a bolt). I'll test it out and may send it to KennyPete for a diagnosis and fix. He's offered to take a look at it for me. Great guy. I'm willing to then pay to have KennyPete get it back to perfect so I can keep it as my nostalgic saw. Means a lot that it's like my dad's old saw.

Anyway, THANKS KennyPete. He's been super helpful off line as well.

Oh, and I did remove and clean out the decompression valve. Didn't looked fouled up but I soaked it in gas and gave it a nice toothbrush scrubs. Couldn't hurt. Appreciate everyone's help.