Well... This sucks!

[dl5205]

Sorry for the bad luck, OP.

Should remind us all to periodically check torque on our fasteners.

 

[dl5205]

I don't think it failed for any other reason than poor installation, and me not checking the saw over good when I got it home.

The saw was really clean and didn't look to be abused at all. I'm not sure why it needed a top end, but I asked the guy about it later and he told me that a "shop" had installed it and he bought the saw from them.

If I'd known then what I know now, I would've asked more questions, and I probably wouldn't have bought the saw.

Makes me wonder why the original jug croaked.

 

[dl5205]

on the up side at least you figured it out before it really blew up! As to the cylinder bolts....a bolt in that situation stays tight by the stretch on the bolt when it is tight. That means the bolt needs to be tightened enough to stretch the bolt longer so it is in tension....that's why there are torque specs to get enough tension on the bolt.....I have found that if you retorque to tighten the cylinder bolts after break in and the gasket settles then that's it it'll stay tight.

good luck

I wonder if we should be installing New cylinder bolts in some instances?

 

[heyduke]

Ditto.

a steel cap screw in aluminum or magnesium threads is self locking. i never use locktite for for cylinder bolts but i often check and re-tighten them after a few hours of running. it only takes a couple of minutes.

 

[cedarshark]

The Stihl service manual calls for 6.6 ft/lbs of torque on the cyl bolts. Thats not very tight. I use blue loc-tite on all of them. Then I dont need to worry about retightening after using the saw for a couple hours.

 

[navgatr]

This happened to me on my 024AVS. This was before I knew anything about saws and I kept trying to use it and re tune it. Amazingly enough, when I finally found the loose jug bolts, there was no damage done to the piston or cylinder. I'm not sure how I got that lucky, but I now check the bolts on all of my saws now.

 

[Agrarian]

I loc-tite all my fasteners and then torque wrench them to spec - seems like cheap insurance but I am not in a business where time is money. One other reason I worried about was if a properly torqued bolt could still provide an air leak. I am not too familiar with Stihl, but Husky's have several bolt that go through to the crankcase. For instance the three bolts that hold on the oil pump on the 242's and 262's. When you remove those bolts you see that the factory has place a red substance on them, I assumed to guarantee no air leaks.

Am I off base with this reasoning?

 

[Marshy]

I wonder if we should be installing New cylinder bolts in some instances?

The amount of stretch of the bolt is dependent on the torque applied and the material of the bolt. As long as the bolts are torqued to the proper load per the OEM they should last nearly "forever" (bolt stress is usally kept between 75-80% yield strength). Given they are threaded into magneasium, I'd put money on the magneasium threads pulling out before the bolt is over loaded or damaged... No reason to replace them that I can see.

 

[heyduke]

The amount of stretch of the bolt is dependent on the torque applied and the material of the bolt. As long as the bolts are torqued to the proper load per the OEM they should last nearly "forever" (bolt stress is usally kept between 75-80% yield strength). Given they are threaded into magneasium, I'd put money on the magneasium threads pulling out before the bolt is over loaded or damaged... No reason to replace them that I can see.

i suspect that in this case (no pun intended) the cylinder bolts may be in steel thread inserts. that would account all of them coming loose. i think he said that one was even missing. there may have been a gorilla wrenching on it that damaged the original threads. locking compound may be a good idea.

 

[Marshy]

Never hurts, just make sure you use the blue grade loctite and not the red!