How often do you check cylinder bolts?

[Moparmyway]

I do remember snugging them down incrementally in an "X" pattern with a Wera t27 screwdriver.

There is the problem.
You can not get cylinder bolts tight enough with just a t27screwdriver

 

[ironman_gq]

Check them after the first heat cycle and one more time after a couple tanks. After that they get checked if something needs to come apart for maintenance.

 

[sevensandeights]

I'm beginning to think this saw is CURSED!!!!!!!!!!!!!!!!!!!!!!

Got my torque wrench and t27 long 3/8" socket today. Went out to torque the bolts. Decided to remove and clean them to help the Loctite 242 work better (243 is supposed to be more oil resistant). Got them all out and cleaned with acetone. Dabbed with Locktite and put them back in. Tightened incrementally in an "X" pattern until they were snug. Set the torque wrench and tightened each one a little bit. One bolt made the torque wrench click much sooner than the others. Started getting that feeling that something wasn't right (bit would snap or bolt would strip). Stopped and reduced the torque from 123 inch lbs to 100. All 4 bolts torqued. Then went up to 110. 3 of the 4 torqued. When working on the last bolt that "feeling" came back and sure enough - SNAP! The bolt snapped but it did not strip out - lesser of the two evils I suppose.

So, dumping more money into the saw. 4 bolts, new base gasket and an HD air filter so I have spare on order. I'll have to take the cylinder off so I can get at the snapped bolt. Don't think there will be enough exposed to attach anything to it - will likely have to try my Norseman left hand drill bit set for the first time.

 

[Bob Hedgecutter]

The saw is cursed- or a case of overkill kills?

 

[sevensandeights]

Could be but that bolt was no longer in spec. Too many heat cycles or something but it shouldn't have snapped. Torque wrench seems like overkill but I don't want them to come loose again after experiencing that once already.

 

[MacAttack]

The thing about putting anything on the threads on a bolt or screw that I am torquing to spec that I am apprehensive about, whether it's oil, never-seize, loctite, etc, is that there is a dry thread torque spec, and a lubricated thread torque spec for fasteners of any given size. The lubricated-threads torque spec is a lower threshold.
Now, I feel like I learn something new everyday, and anyone is welcome to tell me to shut up and that I'm wrong, but I believe there is some risk that a lubricated fastener can pull itself apart before it reaches it's dry thread torque spec. With lubricated threads, it's possible to overstretch and break before the dry torque spec is reached.
When you torque a fastener, what you are essentially doing is stretching it to a given point. I remember from an old job in a NASCAR shop, the rod bolts would get user a few times and then got tossed once they were stretched to a specific limit.
So...I could be talking out of my a$$, and the busted screw may have been damaged or fatigued, or it might have broke because of the loctite.

 

[Bob Hedgecutter]

The thing about putting anything on the threads on a bolt or screw that I am torquing to spec that I am apprehensive about, whether it's oil, never-seize, loctite, etc, is that there is a dry thread torque spec, and a lubricated thread torque spec for fasteners of any given size. The lubricated-threads torque spec is a lower threshold.
Now, I feel like I learn something new everyday, and anyone is welcome to tell me to shut up and that I'm wrong, but I believe there is some risk that a lubricated fastener can pull itself apart before it reaches it's dry thread torque spec.
When you torque a fastener, what you are essentially doing is stretching it to a given point. I remember from an old job in a NASCAR shop, the rod bolts would get user a few times and then got tossed once they were stretched to a specific limit.
So...I could be talking out of my a$$, and the busted screw may have been damaged, or it might have broke because of the loctite.

Simple answer to that- is loctite specified by the manufacturer in service manuals?
You know, the guys that publish the torque settings- do they ever mention coating the threads with an adhesive?

 

[MacAttack]

Simple answer to that- is loctite specified by the manufacturer in service manuals?
You know, the guys that publish the torque settings- do they ever mention coating the threads with an adhesive?

I haven't seen it mentioned to use loctite for the engine parts in the old service manuals I have for my old McCullochs, etc. The OP would have to tell us if his manual mentions it.
If I don't see something called out, I assume dry, clean threads.

 

[PV Hiker]

Correct! Lubing the bolt gives you a false reading and easy to over torque. Some specifications will call out to lube the threads or give wet / dry specifications. I have seen specifications with a low end and a high values called out giving you a safety margin. Most torque wrenches are not calibrated so a value would have some margin of safety at the target point. Sorry you are having such issues with your project.

To add for the Stihl torque specs in my limited chainsaw repairs I have not seen but one value and would assume be dry threads.

 

[sevensandeights]

All good points. I think I'm going to with no locktite on the new bolts. Not much room for error with such a small bolt and an aluminum housing. Torque to spec and check again after a few tanks. that I can get the bolt out.

 

[Bob Hedgecutter]

All good points. I think I'm going to with no locktite on the new bolts. Not much room for error with such a small bolt and an aluminum housing. Torque to spec and check again after a few tanks. that I can get the bolt out.

Before the loctite cures and you break the other three trying to get them out.

 

[Hulsty]

I built my 6401 -> 7901 about a year ago, bolts in dry, torqued to spec not a problem since.

 

[MacAttack]

All good points. I think I'm going to with no locktite on the new bolts. Not much room for error with such a small bolt and an aluminum housing. Torque to spec and check again after a few tanks. that I can get the bolt out.

I'd try to get the threads in the block as clean as possible, not sure what dissolves loctite the best but probably something with acetone in it.
Like my previously disclaimer, I feel like lately some of the things I always accepted as being true I have been made to rethink... but it seems like fasteners rely on either a specific torque value stay tight, or loctite, but in my experience not both.
So I think that with new hardware, torqued to the correct spec with no loctite, you should be good.

 

[Huskybill]

On the bikes after a few heat cycles it’s retorqued. If not the thin base gasket can get sucked in. Even on the new bikes I seen the gasket fail. Tighten once check twice. The husky dirtbike pistons were $200.

 

[sevensandeights]

Before the loctite cures and you break the other three trying to get them out.

I had the same concern last night so I took them all out immediately.

 

[cookies]

That bolt was compromised before you torqued it to spec, most likely it was stretched by being the one bolt holding the cylinder on yet was still loose enough the cylinder beat against it until it stretched enough other bolts shared the load. Using oil/locktite etc is not enough to cause failure on a regular torque to measured force fastener, a torque to yield fastener is a different can of worms. Check the holes for slop and damaged threads, I would look at chicago latrobe,drill hog, matco, snapon for left hand drills.

 

[JayPopple]

If the jug has been off I check em after a tank or 2 and always use loctite 242/3. Never found a loose one on anything I've been fiddling with. Found plenty of missing screws and bolts on other blokes saws though

The standard for automotive and small engines head removed and reinstalled used to be: start and run to normal operating temperature, shut down and retorque to the correct values while still hot. After that it should seal and work without retorquing unless an issue developed.

 

[MacAttack]

That bolt was compromised before you torqued it to spec, most likely it was stretched by being the one bolt holding the cylinder on yet was still loose enough the cylinder beat against it until it stretched enough other bolts shared the load. Using oil/locktite etc is not enough to cause failure on a regular torque to measured force fastener, a torque to yield fastener is a different can of worms. Check the holes for slop and damaged threads, I would look at chicago latrobe,drill hog, matco, snapon for left hand drills.

I have a small set of Irwin left hand bits / extractors that are pretty decent. I guess it depends how small of a bolt are we talking about here? Is this thing as small as a 10-32 screw? (Im sure it's metric)

 

[ironman_gq]

The thing about putting anything on the threads on a bolt or screw that I am torquing to spec that I am apprehensive about, whether it's oil, never-seize, loctite, etc, is that there is a dry thread torque spec, and a lubricated thread torque spec for fasteners of any given size. The lubricated-threads torque spec is a lower threshold.
Now, I feel like I learn something new everyday, and anyone is welcome to tell me to shut up and that I'm wrong, but I believe there is some risk that a lubricated fastener can pull itself apart before it reaches it's dry thread torque spec. With lubricated threads, it's possible to overstretch and break before the dry torque spec is reached.
When you torque a fastener, what you are essentially doing is stretching it to a given point. I remember from an old job in a NASCAR shop, the rod bolts would get user a few times and then got tossed once they were stretched to a specific limit.
So...I could be talking out of my a$$, and the busted screw may have been damaged or fatigued, or it might have broke because of the loctite.

They do have modifier tables to give you the correct torque value with a given dry torque spec. You probably need to be around 70% of the dry torque spec

 

[sevensandeights]

Some good news today. Broken bolt came out without much trouble using lefthand drill bits.


Question about base gasket. My research indicated the ridge should face up. Does anyone disagree? 1st pic is the ridge side and 2nd pic is the other side.