generator mounting bolt missing

[CutterBill]

...Then, as I was cleaning the dried anti-seize off of them, I noticed there was aluminum in the threads of the #2 plug.  Sure enough, I unpeeled the cylinder threads right off of the plug. 

Interesting.  Now I'll tell my story...

Back in the days of the Red Dog Saloon, I owned an auto repair shop. I had 3 full-time mechanics and a summer-time helper.  We were busy. It was common to have 30-40 cars in the back, waiting to be worked on.  Needless to say, we changed a LOT of spark plugs. (This was before the use of unleaded gas and 100,000 mile spark plugs.)  We worked on pretty much everything, with a lot of aluminum heads.  Porsche, Mercedes, a thousand VW's, Japanese stuff, American stuff... One of my mechanics owned a Formula Ford race car so that was in the mix.  And we always used Permatex High-Temp Anti-Seize on any spark plug that went into an aluminum head.  And not once in the 7 years that I owned the shop did we have a problem with the anti-seize.  I also used it on exhaust systems, which get a whole lot hotter than a cylinder head. Four or more years later when the exhaust system had to come back apart, the nut and bolts simply unscrewed. They looked so good that they could be reused. And even at the crazy high temps that exhaust systems run at, I never saw any evidence of the anti-seize breaking down.

Aircraft exhaust systems commonly have slip joints. This is so that the pieces of pipe can expand and contract without undue stress. The joint is a rather snug male-female type with no clamps. I use the same anti-seize on these joints when I put them together. And I have taken them apart years later, and the pipes just slip apart with no galling or rust.  And to explain further, some aircraft exhaust systems (usually with turbos) are made of Inconel because they run so hot that normal stainless steel won't hold up.  And I have never had or even heard of a problem with anti-seize.

Did you know that we are required to use anti-seize on airplane spark plugs? But this may not be a direct apples-to-apples comparison because all aircraft heads have heli-coils installed.  But no one ever worries about the anti-seize breaking down.

Backing up a bit... I got my first motorcycle (a well-used Honda CL350) when I was 15. I didn't know anything about turning wrenches. The spark plugs were so tight that they would squeak coming out. The local Yamaha shop owner (good guy, took me under his wing) told me about using anti-seize.  And I have used it on every bike since. so... 48 years.  Forty-eight years of using Permatex Anti-Seize on motorcycles, cars, boats and even airplanes... and I never, not once, had a problem.  Now Hooligan, I'm not saying that your experience didn't happen. But do I have an idea why...

Obviously, the anti-seize did not dissolve the threads. And I don't believe that you stripped the head threads when you loosened the plugs. Aluminum threads wrapped around the spark plug is the classic symptom of an over-tightened plug.  But you didn't over-tighten it, so how did the threads pull out?

First, it's important to realize that heat is a really bad thing for aluminum.  Aluminum gets weaker as the temperature goes up.  By 400 degrees (F) it has lost half of it strength. And it's really easy to hit 400 degrees. I know this because airplane engines, being air-cooled, have no water temp gauge, so a cylinder head temperature (CHT) gauge is installed in the instrument panel. And on warm days or slow speed we watch that gauge like a hawk. When an engine overhaul costs around $25,000, you tend to pay attention to such things. And it's alarming to see how easy it is to reach the 350-degree maximum. (I  think it would be really interesting to put a CHT gauge on an FJ.)

I believe that you applied anti-seize to the spark plugs and carefully tightened them to the recommended torque value. But because anti-seize is such a good lubricant, you actually tensioned the plugs too much.  (Hence, the warning on the NGK website that Randy referred to.) So now the plugs were too tight, but the aluminum threads held just fine... when the engine was cold.  Then you rode the bike and, somewhere... summer, stop-and-go traffic, high-speed... the engine got hot. Really hot...

Once it got really hot, probably 400 or higher, the aluminum became much weaker. The plug still had tension on it. So now you had a plug with the proper torque, but too much tension, threaded into aluminum that got weaker as the temp went up. Finally, the tension was more than the weak aluminum could withstand, and the threads sheared off. But the plug didn't pop out because the sheared threads jammed the plug in the head. Later, you unscrewed the plug (with great difficulty) and the threads came out with it.

Sorry for your troubles.

Anti-seize is good stuff, but you need to have a very light touch with the wrenches when you use it.
Bill

[fjbiker84]

With the considerable help and expertise at the FJMonkey Garage we were able to extract the one remaining bolt and then gain access to the broken off bolt.  Mark was able to unscrew the broken bolt by hand with a sharp screwdriver.  The remaining bolt was in very tightly so I'm assuming it is a combination of being installed too tight (by the factory) and 33 years of aging.  One problem we noticed while reassembling everything was that approximately half of the surface around the bolt hole was cracked and that piece of metal actually came off.  Mark was able to "glue" this piece back in place with a gasket sealant compound (I think that's what he said he was using) such that the generator could then be reinstalled and the flange would have a flat surface to secure to.  Clearly, the broken bolt must have been way over tighten also. Many thanks to FJMonkey for his help today with this and, in addition, teaching me how to adjust the valves, properly clean and oil the pod filter, and do other maintenance - he also synced the carbs - which is something I'll leave to a pro!

[fjbiker84]

This is the broken off bolt that Mark removed.

[FJmonkey]

Today was a great example of "I would rather be Lucky than Good". The alternator bolt broke loose with a 6 point socket (a few hits with a hammer to seat it). Way harder to turn than a bolt that size should be. I did not see any evidence of thread lock but clear signs of corrosion. Then when figuring out how to hit the broken stud with a center punch, it moved. Grabbed a pick and the stud just backed right out. I thought the worst after the difficulty with the corrosion of the upper bolt. Cleaned up some over oiled UNI pods and reinstalled. Checked the valves just cuz we nearly had it all apart anyway. Found some out of spec gaps and made the corrections. A quick balance of the carbs and adjust idle and we wrapped it up. I enjoyed the day and the company.

Tim, post the picture of the part of the boss that broke off for Randy to see. I only used blue lock-tite paste to hold in place so the alternator flange did not get any funky side loading. It will fall off next time the alternator is removed. Maybe some JB weld when there is time for it to cure. 

[Mark Olson]

way to go Monkey , you are a fine example of the FJ group. always there to help somebody out. 

[Pat Conlon]

Yea, good on ya Mark

[fjbiker84]

Unfortunately I didn't take a picture of the little piece of metal that broke off.  If you look closely at the bolt hole you can see that the left half of the metal surface is where the piece broke from.  I would think in the future if it became necessary I could grind down the metal around that hole and use a small washer was a shim. 

[FJmonkey]

I forgot to mention that Tim's engine runs very quiet. I was a bit shocked because he has stock pipes, so little noise from exhaust. No starter chain rattle or the other "I am talking to you" noises from the engine. Aside from the age of plastics it is clear that the PO took very good care of his FJ. Tim is doing the same and keeping the '84 alive and strong.

[racerrad8]

.....We went to remove the plugs and two pulled the threads. He went on to tell me he "always" uses anti-seize on the spark plugs.


......The spark plug holes are almost as often as the drain plug in the oil pan, we probably forty or more of those per year.

Randy - RPM

The greater number of sump plugs to spark plugs Randy mentions repairing (which is actually even higher number given the 4:1 ratio of spark plugs to sump plugs per engine) is telling. Sump plugs are metal to metal and refitted without anti seize and yet these get stripped at 4 times the rate of spark plugs. I suspect torqure is relative to the fear of them falling out and that leads owners to over tighten them "just to make sure"

Noel

Actually I chalk up the oil pan stripped thread to the 80% thread engagement of the oil pan threads and the fact in the race car some people change their oil after every race day/night. If it comes in & out 2-4 time a month the aluminum is going to fail. Plus people very seldom replace the oil plug gasket...

Plus the torque value Yamaha has on the plug which is double of the spark plugs.

I only use the Heli-Coil so the oil can still drain through the insert. Other solid inserts leave 3/4" of dirty oil in the pan.




That's my opinion based on everything I was taught, everything I learned, everything I've practiced and everything I've experienced in a lifetime as a mechanic. As well as working basically solely on the FJ lump for the past 23 years and not just my personal bike.

Randy - RPM

[jscgdunn]

Randy,
Do you snip the coils off after installation?

Thanks,

Jeff

[racerrad8]

Randy,
Do you snip the coils off after installation?

Thanks,

Jeff

No, the spiral heli-coil allows the oil to drain through. I will snap a photo of the next one I heli-coil.

Don't let me forget...

Randy - RPM

[Pat Conlon]

Randy, if you don't cut the coils, what am I looking at in the picture?

A trimmed Time-Sert?

[racerrad8]

Randy, if you don't cut the coils, what am I looking at in the picture?

A trimmed Time-Sert?

A stock pan

Here is one with a the heli-coil installed.

I took one with a light showing through the gap in the heli-coil.

Randy - RPM

[jscgdunn]

Thanks got it!

[racerrad8]

I got an email last night from the guy with the two XJR1300's in SoCal. He pulled the #4 plug and the threads galled at the very top.

So, since all of the threads did not gall, how does one explain the galling of the upper threads?

Randy - RPM