026 Cylinder Screws Came Loose - Loctite required?

[appyacres]

I rebuilt an 026 that came in a basket. New cylinder and piston and complete bottom end replacement. I also replaced the old carb with a 194 so I could adjust the high speed since the original carb had no high speed screw. Saw took a while to tune but I was able to get it to 4 stroke, then backed off the high speed screw about 1/8th turn. Had a lot of trouble getting the throttle response and idle set, but after running the saw a few times, 3 or 4 tanks of gas, and retuning, the idle improved to a tolerable level.

Two days ago I was using the saw and it died and would not idle at all. Tore the top end down today and found one of the cylinder screws had fallen out. The other three were loose and the cylinder was moving a bit. No wonder it didn't run right.

The question is, was I suppose to retorqued the screws after running for a few hours or should I have used loctite, blue or red, to prevent this problem?

I looked in the manual and it said nothing about loctite and the torque value was 7.7 lbs.

 

[cgraham1]

Stihl screws backed out? My guess is that you didn't put them in tight enough in the first place... but it wouldn't hurt to recheck everything after running for a while.

 

[Chainsaw Jim]

Make sure they're the ones with the locking teeth under the head and no washer. Clean all the screws and the holes with carb cleaner to make sure they are as clean and dry as possible before tightening down

 

[LowVolt]

I usually make sure I tighten them like I tighten lug nuts on a car tire so you get all of them evenly tight.

 

[appyacres]

Back together and running again.

Stock Stihl screws. Cleaned threads of the screws and threads in the case with contact cleaner as suggested. Compressed air to remove any residuals. Reinstalled cylinder and used a bit of blue loctite to be sure. Torqued first to 60 in-lbs followed by 95 in-lbs in cross pattern. Finished remainder of motor assembly and just before installing the top cover, verified once again the screws were torqued to 7.7 ft-lbs with a second torque wrench.

Easy retune after running for a few minutes to warm up. I will recheck torque after running a few tanks of gas this time.

Thanks for the responses and this forum to help me spend my spare cash.

Yesterdays project was a Farm Boss MS290 a friend blew up. Put a 390 motor in it and was cutting wood in 4 1/2 hours. Tomorrow I am going to rebuild another MS290 I picked up. Bought 2 of the 390 motors for these projects.

Funny thing is, I don't even have a fireplace or wood stove. I do have 3 working saws and soon to have a fourth! grins...

 

[Chainsaw Jim]

I've noticed torque specs being a tad light on occasion or they'll have a range. You can feel threads lock without a torque wrench and that pressure can be as much as a half a pound more than specification.
I don't set my torque wrench higher, I just give a little nudge by hand to make sure all the screws are locked down and don't turn any tighter.

 

[Homelitexl903]

Hey appyacres it's normal actually. I have around 30 saws now and don't heat with wood. I do it for fun and outdoor firepit wood and side jobs. It's like owning a bunch of guns and you only target practice. We call it Chainsaw addiction disorder or CAD.

 

[cgraham1]

I just use my t-handle and snug em up until they feel tight. I've never had any jug bolts back out, that I installed.

 

[Down Home Dave]

Checking these screws is a part of my routine maintenance after heavy use. I have been burned before by a loose jug. first thing i check before adjusting a formerly well running saw that acts like it has an air leak. i now clean those screws and lightly blue loctite- and only replace with stihl "spline screws."